Patent Description:
A water cleaner for purifying water frequently uses an activated carbon as was disclosed in <CIT> and <CIT>, for example. Further, a water cleaner is frequently attached directly to, for example, a water outlet and used.

<CIT> discloses a porous carbon material suitable for incorporation in smoke filters for cigarettes having a BET surface area of at least <NUM> m2/g and a pore structure that includes mesopores and micropores.

<CIT> discloses a two-stage design for a water purification system, with water to be purified first passing through a first stage containing particulate filtration media, and a second stage containing a porous filtration block which comprises a porous carbon material.

<CIT> and <CIT> provide a porous carbon material using a plant-derived material having a silicon content of <NUM> wt. % or more as a raw material, having a specific surface area value by a nitrogen BET method of <NUM><NUM>/gram or more, a silicon content of <NUM> wt. % or less, and a pore volume by a BJH method and an MP method of <NUM><NUM>/gram or more.

In such a conventional water cleaner, there is a problem that when a filtration flow rate is large, that is, when a flow rate of water flowing through a water cleaner is large, in some cases, a water purifying function cannot be fully exerted. Further, in order to increase a specific surface area, a powdered activated carbon is frequently used. In this case, there may be a problem that a powdered activated carbon leaks out of a water cleaner together with purified water. Further, there is a strong demand for a decontaminant, a carbon/polymer composite, and a decontamination sheet member, which can more effectively remove a contaminant. Still further, there is also a demand for controlling the water hardness by flowing through a filter medium. However, as far as the inventors have investigated, a technology that can achieve such a demand has not been known.

Therefore, an object of the present invention is to provide a method for producing a decontaminant which can more effectively remove a contaminant. The above object is solved by the claimed matter according to claim <NUM>.

The method for producing a decontaminant according to the present invention as defined in claim <NUM> for achieving the object comprises.

to obtain a decontaminant in the form of a porous carbon material:.

A carbon/polymer composite (not according to the present invention) may include the decontaminant in form of the porous carbon material produced according to the method of of the present invention, and a binder.

A filter medium (not according to the present invention) may include the decontaminant in form of the porous carbon material produced with the method according to the present invention.

In the decontaminants produced in the method according to the present invention, since a value of a specific surface area, a value of volumes of various kinds of fine pores and a pore distribution of a porous carbon material used are specified, a contaminant can be removed at a high efficiency, a fluid can be cleansed at a high filtration flow rate, and a desired substance can be removed at a high efficiency. Further, since a particle size of a porous carbon material is specified, it is difficult for a porous carbon material to flow out together with a fluid. In the decontaminants produced in the method according to the present invention, in addition to adsorption of contaminants, for example, on the basis of a chemical reaction such as HClO + C (porous carbon material) -> CO (surface of porous carbon material) + H+ + Cl-, the chlorine component can be removed. Further, in the filter media, since a value of a specific surface area, a value of volumes of fine pores, and a pore distribution of a porous carbon material used are specified, and a raw material is specified, hardness of the water that has passed through the filter medium can be controlled.

The following figures refer to the examples, whereby in Tables <NUM> to <NUM> it is explicitly stated which example contains a decontaminant produced by the method according to the invention and which does not.

Hereinafter, with reference to drawings, the present invention will be described based on Examples. However, the present invention is not limited to the Examples. Various kinds of numerical values and materials in the Examples are illustrations. Description will be carried out in the following order.

In porous carbon materials which make up the decontaminants produced according to the present invention a bulk density of the porous carbon material is <NUM>/cm<NUM> to <NUM>/cm<NUM>,. When the bulk density of the porous carbon material is specified as in the above range, there is no fear that the porous carbon material disturbs a flow of a fluid. That is, the pressure loss of a fluid, which is caused by the porous carbon material, can be suppressed.

The porous carbon material of the produced decontaminant in the present invention is specified to have a particle size of <NUM> or more. Such a specification is based on<NPL>". That is, when a test is conducted by using a metal mesh having a nominal opening of <NUM> (so-called metal mesh of <NUM> (<NUM> mesh)) and a porous carbon material that does not pass the metal mesh is <NUM>% by mass or more, a particle size is defined to be <NUM> or more. Further, in the following description, such a porous carbon material is called as "<NUM> on the product" ("<NUM> mesh on product") and a porous carbon material that passed the metal mesh of <NUM> (<NUM> mesh) is called as "<NUM> pass product" ("<NUM> mesh pass product"). When a particle size is measured, the measurement is conducted in a state where the porous carbon material is used, that is, in a state including primary particles and secondary particles generated by flocculation of a plurality of primary particles.

Further, a measurement of fine pores by mercury porosimetry is conducted in accordance with <NPL>". Specifically, by using a mercury porosimeter (trade name: PASCAL440, manufactured by Thermo Electron Corporation), mercury porosimetry was conducted. A fine pore measurement region was set to <NUM> to <NUM>.

The decontaminant produced according to the method of the invention can be used for cleaning, for example, water or air, broadly, for cleaning a fluid. Alternatively, the decontaminant produced according to the method of the present invention can be used as a remover for removing, for example, a harmful material or a waste material. The decontaminant produced according to the method of the present invention can be used in a form of a sheet, in a state filled in a column or a cartridge, in a state housed in a water-permeating bag, in a state formed into a desired shape with a binder, or in a state of powder, for example. In the case where the decontaminant is used being dispersed in a solution, a surface thereof can be subjected to hydrophilic or hydrophobic treatment, to be used. From the carbon/polymer composite or the decontamination sheet member, for example, a filter for an air purifier, a mask, a protective glove and protective shoes can be formed.

In the decontamination sheet members a woven fabric or a nonwoven fabric can be mentioned as a support member, and as a material forming the support member, cellulose, polypropylene and polyester can be mentioned. As a form of the decontamination sheet member, a form in which the porous carbon material is sandwiched between one support member and another support member, and a form in which the porous carbon material is blended in a support member can be mentioned. Alternatively, as a form of the decontamination sheet member, a form in which the carbon/polymer composite is sandwiched between one support member and another support member and a form in which the carbon/polymer composite is blended in a support member can be mentioned. As a binder which make up the carbon/polymer composite, for example, carboxynitrocellulose can be mentioned.

A purification apparatus suitable for incorporating the filter medium , specifically, a water cleaner may have a structure (combined use of the filter medium and a filtration membrane) that further includes a filtration membrane (for example, hollow fiber membrane or flat membrane having <NUM> to <NUM> holes), a structure (combined use of the filter medium and a reverse osmosis membrane) that further includes a reverse osmosis membrane (RO), a structure (combined use of the filter medium and a ceramic filter medium) that further includes a ceramic filter medium (ceramic filter medium having fine pores), or a structure (combined use of the filter medium and an ion exchange resin) that further includes an ion exchange resin. In general, filtrate water passed through a reverse osmosis membrane (RO) would hardly contain a mineral component. However, by passing through a reverse osmosis membrane (RO) and then passing through a filter medium, a mineral component can be imparted to the filtrate water.

As types of the water cleaners, a continuous water cleaner, a batch water cleaner and a reverse osmosis membrane water cleaner can be mentioned, or a faucet-coupled water cleaner in which a water cleaner body is directly attached to an tip part of a water faucet, a stationary water cleaner (also referred to as top sink water cleaner or table top water cleaner), a water faucet-integrated water cleaner in which a water cleaner is incorporated in a water faucet, a under-sink water cleaner that is installed in a sink of a kitchen (built-in water cleaner), a pot water cleaner in which a water cleaner is incorporated in a container such as a pot and a pitcher (pitcher water cleaner), a central water cleaner that is directly attached to a water pipe after a water meter, a portable water cleaner and a straw water cleaner can be mentioned. The water cleaner can have a constitution and structure the same as those of a water cleaner of the past. In the water cleaner, a filter medium (porous carbon material) can be used in a cartridge, for example, and to the cartridge, a water inlet and a water outlet may be provided. The "water" that is a target of purification in the water cleaner is not limited to the "water" defined in<NPL>".

Alternatively, as a member suitable for incorporating the filter medium, a cap or a cover in a bottle (so-called PET bottle), a laminate container, a plastic container, a glass container, a glass bottle, which are provided with a cap, a cover, a straw member, or a spray member can be mentioned. Here, when a filter medium is disposed inside a cap or a cover, and a liquid or water (drinkable water, a lotion, or the like) in a bottle, a laminate container, a plastic container, a glass container, a glass bottle or the like is passed through the filter medium disposed inside the cap or cover and is drunk, or used, a mineral ingredient can be contained in filtrate water. Alternatively, a form in which the filter medium is housed in a bag having water permeability, and the bag is put in a liquid or water (drinkable water, a lotion, or the like) inside various kinds of containers such as a bottle (so-called PET bottle), a laminate container, a plastic container, a glass container, a glass bottle, a pot and a pitcher, can be adopted.

The raw material of a porous carbon material used in the present invention is a plant-derived material containing silicon (Si), specifically, a content of a residue on ignition (ash residue) in a porous carbon material is <NUM>% by mass or less. Further, a content of a residue on ignition (ash residue) in a porous carbon material precursor or a carbonaceous substance, which will be described below, is desirably <NUM>% by mass or more. Here, a residue on ignition (ash residue) indicates a percentage by mass of a substance remained when a specimen dried at <NUM> for <NUM> hours is heated up to <NUM> in air (dry air), and, specifically, can be measured based on a thermogravimetric (TG) method.

The porous carbon materials or porous carbon materials which can make up filter media is obtained in such a manner that after a plant-derived material is carbonized at <NUM> to <NUM>, the carbonized material is treated with an acid or an alkali. In the method for producing a decontaminant in form of a porous carbon material, a material that is obtained by carbonizing the plant-derived material at <NUM> to <NUM> and before an acid or alkali treatment is applied is called as a "porous carbon material precursor" or a "carbonaceous substance".

In the method of the invention, after an acid or alkali treatment, a step of conducting an activation treatment is included, and, after the activation treatment, an acid or alkali treatment is conducted. Further, in the method, although depending on the plant-derived material being used, before carbonizing the plant-derived material, at a temperature of from <NUM> to <NUM>, lower than a temperature for carbonizing, the plant-derived material may be preheated (pre-carbonizing treatment) in a state where oxygen is shut off. Thereby, since a tar component that would be generated in the course of carbonization can be extracted, the tar component that would be generated in the course of carbonization can be reduced or removed. A state where oxygen is shut off can be achieved by using, for example, an inert gas atmosphere such as nitrogen gas and argon gas, or a vacuum atmosphere, or a kind of smothering state of the plant-derived material. Further, in the method of the present invention, though depending on the plant-derived material, in some cases, in order to reduce mineral components or moisture contained in the plant-derived material, or, in order to prevent an unusual odor from occurring in the course of carbonization, the plant-derived material may be dipped in an acid or alkali, or in alcohol (for example, methyl alcohol, ethyl alcohol, or isopropyl alcohol). In the method of the present invention, after that, a pre-carbonizing treatment may be conducted. Examples of materials that are desirable to be heated in an inert gas atmosphere include plants that abundantly generate pyroligneous acid (tar and light oil). Further, examples of materials that are desirable to be treated with alcohol include seaweeds that abundantly contain iodine or various kinds of minerals.

According to the method of the present invention, the plant-derived material is carbonized at <NUM> to <NUM>. Here, the carbonization generally means to heat an organic substance (porous carbon material or a plant-derived material in a porous carbon material that can make up filter media ) to convert to a carbonaceous substance (for example, see JIS M0104-<NUM>). As an atmosphere for carbonization, an atmosphere where oxygen is shut off can be mentioned, and, specifically, a vacuum atmosphere, an inert gas atmosphere such as nitrogen gas and argon gas, and an atmosphere where a material of plant origin is put into a kind of smothering state can be mentioned. An example of a rate of temperature increase until reaching the carbonization temperature, under such an atmosphere, may be <NUM>/ min or more, desirably <NUM>/ min or more, and more desirably <NUM>/ min or more, but is not limited thereto. Further, an example of the upper limit of a carbonization time may be <NUM> hours, desirably <NUM> hours, and more desirably <NUM> hours, without particularly limiting thereto. The lower limit of a carbonization time can be set to a time where the plant-derived material is surely carbonized. Further, the plant-derived material may be pulverized to a desired particle size, and may be classified, as desired. The plant-derived material may be pre-washed. Alternatively, the obtained porous carbon material precursor or porous carbon material may be pulverized to a desired particle size, and may be classified, as desired. Or, the porous carbon material after the activation treatment may be pulverized to a desired particle size, and may be classified, as desired. Further, the finally obtained porous carbon material may be subjected to sterilization treatment. Without particularly limiting a type, a formation, and a structure of a furnace used for carbonization, either a continuous furnace or a batch furnace can be used.

In the method, as was described above, an activation treatment is conducted, the number of micro pores (described below) having a pore diameter smaller than <NUM> can be increased. As a method of the activation treatment, a gas activation method is used. Here, the gas activation method is a method by using oxygen, water vapor, carbon dioxide or air as an activator, and by heating a porous carbon material under such an atmosphere, at <NUM> to <NUM>, desirably at <NUM> to <NUM>, and more desirably at <NUM> to <NUM>, for several tens of minutes to several hours, so that a fine structure is developed due to volatile components or carbon molecules in the porous carbon material. More specifically, a heating temperature may be appropriately selected based on a type of the plant-derived material, a type and a concentration of gas.

On a surface of a porous carbon material, or, on a surface of a porous carbon material that can make up a filter medium , a chemical treatment or a molecular modification may be applied. As a chemical treatment, for example, a treatment in which carboxyl groups are generated on the surface by a nitric acid treatment can be mentioned. Further, by conducting a treatment the same as the activation treatment with water vapor, oxygen, alkali, or the like on the surface of the porous carbon material, various kinds of functional groups such as a hydroxyl group, a carboxyl group, a ketone group and an ester group can be generated. Further, by reacting with a chemical species or a protein having a hydroxyl group, a carboxyl group, an amino group, or the like, which is capable of reacting with a porous carbon material, a molecular modification can be conducted.

According to the method, by treating with an acid or an alkali, a silicon component in the plant-derived material after carbonization is allowed to be removed. Here, as a silicon component, silicon oxides such as silicon dioxide, silicon oxide, and silicon oxide salts can be mentioned. Thus, when the silicon component in the plant-derived material after carbonization is removed, a porous carbon material having a large specific surface area can be obtained. In some instances, a dry etching method may be used to remove the silicon component in the plant-derived material after carbonization. Further, for example, by dipping in an inorganic acid such as hydrochloric acid, nitric acid and sulfuric acid, a mineral component contained in the plant-derived material after carbonization may be removed.

Porous carbon materials may have a plant-derived material as a raw material. Here, as a plant-derived material, husks and straws of rice, barley, wheat, rye, Japanese millet, foxtail millet; coffee beans, tea leaves (for example, leaves of green tea and black tea), sugar canes (more specifically, bagasse), corns (more specifically, cores of corns), above-described fruit skin (for example, skin of citrus fruits such as mandarin orange, and skin of banana), or reeds and Wakame stems can be mentioned without limiting thereto. Other than the above, for example, vascular plants that live on land, ferns, bryophytes, algae, and seaweeds can be mentioned. These materials may be used singularly or in a combination of several kinds thereof as a raw material. Further, both a shape and a form of the plant-derived material are not particularly limited, for example, husks or straws may be used as it is, or dried products can be used. Further, materials after various kinds of processing such as fermentation process, roasting process and extraction process, in food and beverage processing of beer, liquor or the like, can also be used. In particular, from the viewpoint of recycling industrial wastes, it is desirable that straws and husks after processing of threshing or the like are used. These straws and husks after processing can be abundantly and readily available, for example, from agriculture cooperatives, alcohol manufacturers, and food-processing companies.

In porous carbon materials, non-metal elements such as magnesium (Mg), potassium (K), calcium (Ca), phosphorus (P) and sulfur (S), and metal elements such as transition elements may be contained. A content of magnesium (Mg) of <NUM>% by mass or more and <NUM>% by mass or less, a content of potassium (K) of <NUM>% by mass or more and <NUM>% by mass or less, a content of calcium (Ca) of <NUM>% by mass or more and <NUM>% by mass or less, a content of phosphorus (P) of <NUM>% by mass or more and <NUM>% by mass or less, and a content of sulfur (S) of <NUM>% by mass or more and <NUM>% by mass or less can be mentioned. Contents of these elements are desirable to be small from the viewpoint of an increase in a value of a specific surface area. A porous carbon material may contain other elements than the above elements, and it goes without saying that also ranges of contents of the various kinds of elements may be altered.

In porous carbon materials, or in porous carbon materials that can make up filter media , various kinds of elements can be analyzed by energy dispersive X-ray spectrometry with, for example, an energy dispersive X-ray spectrometer (for example, JED-2200F manufactured by JEOL). Here, measurement conditions may be set to, for example, a scanning voltage of <NUM> kV and an irradiation current of <NUM>µA.

Porous carbon materials, or porous carbon materials that can make up filter media have many fine pores. As a fine pore, a "meso fine pore" having a pore diameter from <NUM> to <NUM>, a "micro fine pore" having a pore diameter smaller than <NUM>, and a "macro fine pore" having a pore diameter exceeding <NUM> are included. In a porous carbon material, a volume of fine pores by an MP method is desirably <NUM><NUM>/g or more, as was described above.

In porous carbon materials, or in porous carbon materials that can make up filter media , a value of a specific surface area by a nitrogen BET method (hereinafter, in some cases, simply referred to as "value of specific surface area") is <NUM> × <NUM><NUM> m<NUM>/g or more, desirably <NUM> × <NUM><NUM> m<NUM>/g or more for obtaining even better functionality.

The nitrogen BET method is a method in which nitrogen as adsorbate molecules is adsorbed onto and desorbed from the adsorbent (here, the porous carbon material) to measure an adsorption isotherm, and the measurement data is analyzed based on a BET formula represented by the formula (<NUM>). Based on this method, a specific surface area, a fine pore volume can be calculated. Specifically, in the case of calculating the specific surface area by a nitrogen BET method, first, nitrogen as adsorbate molecules is adsorbed onto and desorbed from the porous carbon material to obtain the adsorption isotherm. Then, from the adsorption isotherm thus obtained, [p/{Va(p<NUM>-p)}] is calculated based on the formula (<NUM>) or on the formula (<NUM>') obtained by modification of the formula (<NUM>), and the calculation result is plotted against the equilibrium relative pressure (p/p<NUM>). Next, regarding the plot as a straight line, the inclination s (=[(C-<NUM>)/(C·Vm)]) and the intercept i (=[<NUM>/(C·Vm)]) of the straight line are calculated based on the least squares method. Then, from the inclination s and the intercept i thus obtained, Vm and C are calculated based on the formula (<NUM>-<NUM>) and the formula (<NUM>-<NUM>). Further, the specific surface area asBET is calculated from Vm based on the formula (<NUM>) (see<NPL>). Incidentally, the nitrogen BET method is a measuring method according to the "<NPL>. <MAT> <MAT> <MAT> <MAT> <MAT>
where.

In the case of calculating the fine pore volume Vp by the nitrogen BET method, for example, linear interpolation is applied to the adsorption data of the adsorption isotherm obtained, and the adsorption amount V at a relative pressure set by a fine pore volume calculation relative pressure is obtained. From this adsorption volume V, the fine pore volume Vp can be calculated based on the formula (<NUM>) (see<NPL>). Incidentally, the fine pore volume based on the nitrogen BET method may hereinafter be referred to simply as "fine pore volume"). <MAT>
where.

The pore diameter of meso fine pores can, for example, be calculated as a pore size distribution from the fine pore volume variation rate relative to the pore diameter, based on the BJH method. The BJH method is a method that is widely used as a pore size distribution analyzing method. In the case of analyzing the pore size distribution based on the BJH method, first, nitrogen as adsorbate molecules is adsorbed onto and desorbed from a porous carbon material to obtain a desorption isotherm. Next, based on the desorption isotherm thus obtained, a thickness of an adsorbed layer at the time of stepwise adsorption/desorption of adsorbate molecules from the condition where the fine pores are filled with the adsorbate molecules (for example, nitrogen) and an inside diameter (twice the core radius) of the pores generated in that instance are obtained, then the fine pore radius rp is calculated based on the formula (<NUM>), and the fine pore volume is calculated based on the formula (<NUM>). Then, based on the fine pore radius and the fine pore volume, the fine pore volume variation rate (dVp/drp) relative to the pore diameter (2rp) is plotted, whereby the pore size distribution curve is obtained (see <NPL>). <MAT> <MAT> where <MAT>
where.

The pore diameter of micro fine pores can be calculated as a pore size distribution from the fine pore volume variation rate relative to the pore diameter, based on, for example, the MP method. In the case of analyzing the pore size distribution by the MP method, first, nitrogen is adsorbed onto the porous carbon material to obtain an adsorption isotherm. Next, the adsorption isotherm is converted into fine pore volume relative to a thickness t of the adsorbed layer (plotted against t). Then, based on the curvature of the plot (variation of fine pore volume relative to variation in thickness t of adsorbed layer), a pore size distribution curve can be obtained (see<NPL>).

In the non-localized density functional theory method (NLDFT method) specified in<NPL>" and<NPL>", a software that comes with an automatic specific surface area/fine pore distribution measuring apparatus "BELSORP-MAX" manufactured by BEL JAPAN, INC. is used as analysis software. A model is formed so as to have a cylindrical shape and carbon black (CB) is assumed as the prerequisite, and a distribution function of a fine pore distribution parameter is set as "no-assumption". The smoothing is carried out ten times for the resulting distribution data.

The porous carbon material precursor is treated with an acid or an alkali. In this case, as a specific treatment method, for example, a method of dipping the porous carbon material precursor in an aqueous solution of an acid or an alkali, or a method of causing the porous carbon material precursor and an acid or an alkali to react with each other in a gas phase can be mentioned. More specifically, when the porous carbon material precursor is treated with an acid, a fluorine compound that shows an acidic property, such as hydrogen fluoride, a hydrofluoric acid, ammonium fluoride, calcium fluoride and sodium fluoride can be mentioned. When the fluorine compound is used, an amount of fluorine elements may be four times larger than the amount of silicon elements in a silicon component contained in the porous carbon material precursor, and a concentration of a fluorine compound aqueous solution is desirably <NUM>% by mass or more. When the silicon components (such as the silicon dioxide) contained in the porous carbon material precursor are removed away by using a hydrofluoric acid, the silicon dioxide reacts with the hydrofluoric acid as shown either in Chemical Formula (A) or in Chemical Formula (B) and is removed away either as a hexafluorosilicic acid (H<NUM>SiF<NUM>) or as silicon tetrafluoride (SiF<NUM>). Thus, a porous carbon material can be obtained. Then, after that, the rinsing and the drying may be conducted. When a porous carbon material precursor is treated with an acid, by treating with an inorganic acid such as hydrochloric acid, nitric acid and sulfuric acid, mineral components contained in the porous carbon material precursor can be removed.

SiO<NUM> + 6HF → H<NUM>SiF<NUM> + <NUM><NUM>O     (A).

SiO<NUM> + 4HF → SiF<NUM> + <NUM><NUM>O     (B).

On the other hand, when the porous carbon material precursor is treated with an alkali (base), sodium hydroxide, for example, can be used as the alkali. When an aqueous solution of the alkali is used, pH of an aqueous solution may be <NUM> or more. When the silicon components (for example, silicon dioxide) contained in the porous carbon material precursor are removed away with an aqueous solution of sodium hydroxide, silicon dioxide reacts with the sodium hydroxide as shown in chemical formula (C) by heating the aqueous solution of sodium hydroxide and is removed away as sodium silicate (Na<NUM>SiO<NUM>), thereby a porous carbon material can be obtained. Also, when the porous carbon material precursor is treated by reacting with sodium hydroxide in a gas phase, silicon dioxide reacts with the sodium hydroxide as shown in chemical formula (C) by heating a solid substance of sodium hydroxide and is removed away as sodium silicate (Na<NUM>SiO<NUM>), thereby a porous carbon material can be obtained. Then, after that, the rinsing and the drying may be conducted.

SiO<NUM> + 2NaOH →Na<NUM>SiO<NUM> + H<NUM>O     (C).

Or, as porous carbon materials, or, porous carbon materials that may form filter media , for example, also a porous carbon material disclosed in <CIT> which includes vacancies having three-dimensional regularity (porous carbon material having a so-called inverted-opal structure), specifically, a porous carbon material which includes spherical vacancies that have an average diameter of <NUM> × <NUM>-<NUM> to <NUM> × <NUM>-<NUM> m being three-dimensionally disposed, and which has the specific surface area of <NUM> × <NUM><NUM> m<NUM>/g or more. Desirably, a porous carbon material which includes vacancies disposed in an arrangement corresponding macroscopically to a crystal structure, or vacancies disposed on a surface thereof in an arrangement macroscopically corresponding to a (<NUM>) plane orientation in a face-centered cubic structure can be used.

Example <NUM> relates to decontaminants produced with the method according to the present invention, carbon/polymer composites (not according to the present invention), decontamination sheet members (not according to the present invention), and filter media (not according to the present invention).

A decontaminant produced according to the method of the present invention or a filter medium of Example <NUM> is formed of a porous carbon material that, according to an expression of a decontaminant or a filter medium , has a value of a specific surface area by the nitrogen BET method of <NUM> × <NUM><NUM> m<NUM>/g or more, a volume of fine pores based on a BJH method of <NUM><NUM>/g or more, desirably <NUM><NUM>/g or more, and more desirably <NUM><NUM>/g or more, and a particle size of <NUM> or more. Further, the decontaminant or the filter medium of Example <NUM> is formed of a porous carbon material that, according to an expression of a decontaminant or a filter medium , has a value of a specific surface area by the nitrogen BET method of <NUM> × <NUM><NUM> m<NUM>/g or more, a total of volumes of fine pores having a diameter of <NUM> × <NUM>-<NUM> m to <NUM> × <NUM>-<NUM> m obtained according to the non-localized density functional theory (NLDFT method) (referred to as "volume A" for convenience) of <NUM><NUM>/g or more, and a particle size of <NUM> or more. Still further, the decontaminant or the filter medium of Example <NUM> is formed of a porous carbon material that, according to an expression of a decontaminant or a filter medium , has a value of a specific surface area by the nitrogen BET method of <NUM> × <NUM><NUM> m<NUM>/g or more, at least one peak in the range of <NUM> to <NUM>, in a pore diameter distribution obtained by a non-localized density function theory, a ratio of a total of volumes of fine pores having pore diameters in the range of <NUM> to <NUM>, with respect to a sum total of volumes of all fine pores, of <NUM> or more, and a particle size of <NUM> or more. Furthermore, the decontaminant or the filter medium of Example <NUM> is formed of a porous carbon material that, according to an expression of a decontaminant or a filter medium , has a value of a specific surface area by the nitrogen BET method of <NUM> × <NUM><NUM> m<NUM>/g or more, a volume of fine pores by mercury porosimetry of <NUM><NUM>/g or more, and a particle size of <NUM> or more.

Fine pores (meso fine pores) by the BJH method, fine pores (micro fine pores) by the MP method, and fine pores by the mercury porosimetry are obtained by removing, at least, silicon from a plant-derived material containing silicon. A volume of fine pores of the porous carbon material by the mercury porosimetry is more desirably <NUM><NUM>/g or more, and a volume of fine pores by the MP method is desirably <NUM><NUM>/g or more. Further, the bulk density of the porous carbon material is <NUM>/cm<NUM> to <NUM>/cm<NUM>.

In Example <NUM>, as a plant-derived material that is a raw material of the porous carbon material, rice (paddy) husk was used. The porous carbon material in Example <NUM> is obtained by carbonizing husk as a raw material into a carbonaceous substance (porous carbon material precursor), followed by treating with an acid. Hereinafter, a method for manufacturing a porous carbon material in Example <NUM> will be described.

In manufacture of a porous carbon material in Example <NUM>, a plant-derived material was carbonized at <NUM> to <NUM> and, after that, by treating with an acid or an alkali, a porous carbon material was obtained. That is, firstly, husks of rice were heated (pre-carbonizing treatment) in an inert gas atmosphere. Specifically, husks of rice were carbonized by heating at <NUM> for <NUM> hours in a nitrogen gas flow to obtain a carbide. When such a treatment is applied, a tar component to be generated in the following carbonizing treatment can be reduced or removed. Thereafter, <NUM> of the carbide was charged in an alumina crucible and heated up to <NUM> at a rate of temperature increase of <NUM>/min in a nitrogen gas flow (<NUM>/min). Then, after carbonizing at <NUM> for <NUM> hour to convert to a carbonaceous substance (porous carbon material precursor), the carbonaceous substance was cooled to room temperature. During carbonizing and cooling, a nitrogen gas was continued to flow. Next, the porous carbon material precursor was treated with an acid by dipping in an aqueous solution of <NUM>% by volume of hydrofluoric acid overnight, and, after that, the resultant was washed using water and ethyl alcohol until pH7 was obtained. Then, after drying at <NUM>, by activating by heating at <NUM> for <NUM> hours in a water vapor (<NUM>/min), a porous carbon material of Example <NUM> was obtained. When the porous carbon material of Example <NUM> was pulverized and sieved, and a portion of <NUM> (<NUM> mesh) pass and <NUM> (<NUM> mesh) on product was sampled, Example 1A was obtained.

By sieving a filter medium used in a commercially available water cleaner, portions of <NUM> (<NUM> mesh) pass and <NUM> (<NUM> mesh) on product were sampled as Comparative Example 1A and Comparative Example 1B. A filter medium in Comparative Example 1A is formed of silica, and a filter medium in Comparative Example 1B is formed of bamboo charcoal.

BELSORP-mini (manufactured by BEL JAPAN INC. ) was used as a measurement instrument for obtaining the specific surface area and the fine pore volume, and a test for adsorbing and desorbing nitrogen was carried out. With regard to the measurement condition, a measurement equilibrium relative pressure (p/p<NUM>) was set in the range of <NUM> to <NUM>. Also, the specific surface area and the fine pore volume were calculated based on the BELSORP analysis software. In addition, the test for adsorbing and desorbing nitrogen was carried out by using the measurement instrument described above, thereby calculating the pore diameter distribution of the meso fine pores and the micro fine pores based on both the BJH method and the MP method using the BELSORP analysis software. In addition, the automatic specific surface area/pore distribution measuring apparatus "BELSORP-MAX" manufactured by BEL JAPAN, INC. was used for the analysis based on the non-localized density functional theory method. It is noted that for the measurement, drying was carried out at <NUM> for <NUM> hours as a pretreatment for a specimen.

When a specific surface area and a volume of fine pores of each of filter media of Example 1A, Comparative Example 1A and Comparative Example 1B were measured, results shown in Table <NUM> were obtained. In Table <NUM>, a "specific surface area" indicates a value of a specific surface area by the nitrogen BET method, and a unit thereof is m<NUM>/g. Further, a "MP method" and a "BJH method" indicate measurement results of volumes of fine pores (micro fine pores) by the MP method and measurement results of volumes of fine pores (meso fine pore to macro fine pore) by the BJH method, respectively, and a unit thereof is cm<NUM>/g. Further, in Table <NUM>, a "volume of all fine pores" indicates a value of a volume of all fine pores by the nitrogen BET method, and a unit thereof is cm<NUM>/g. Still further, a ratio (volume ratio) of a total of volumes of fine pores having a pore diameter in the range of <NUM> to <NUM> with respect to a total of volumes (volume A, sum total of volumes of all fine pores) of fine pores having a pore diameter of <NUM> × <NUM>-<NUM> m to <NUM> × <NUM>-<NUM> m based on the non-localized density functional theory method (NLDFT method) is shown in Table <NUM>. Here, although measurement results of a fine pore volume based on the BJH method and a sum total of volumes of all fine pores (volume A) based on the NLDFT method show large values in Comparative Example <NUM>, this is because a filter medium in Comparative Example 1A is not formed of a porous carbon material but is formed of silica.

In order to measure an adsorption amount, aqueous solutions each containing <NUM> mol/L of Methylene blue and <NUM> mmol/L of Black <NUM> were prepared, <NUM> of a specimen was charged in each of <NUM> aqueous solutions. The solutions were stirred at <NUM> rpm with a mix rotor (stirrer) for <NUM> minute, <NUM> minute, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes and <NUM> minutes, after stirring, the solutions were filtrated, and, based on a test method that measures an absorbance change of the resulted filtrate, a relationship between a stirring time and an adsorption amount of each of Methylene blue and Black <NUM> per <NUM> of filter medium was calculated from a value of a calibration curve obtained from absorbance per unit mass.

Results thereof are shown in (A) and (B) of <FIG>. Adsorption amounts of Methylene blue and Black <NUM> of a filter medium of Example 1A are remarkably larger than those of filter media of Comparative Example 1A and Comparative Example 1B. This is considered that it is because a large volume of meso fine pores and macro fine pores, which are not observed in Comparative Examples, had an influence. Here, a vertical axis in <FIG> shows an adsorption amount (unit: mg/g), and a horizontal axis shows a test time (time during which a filter medium is dipped in a test liquid, unit thereof is minute). Further, a triangle mark shows data of Example 1A, a square mark shows data of Comparative Example 1A, and a circle mark shows data of Comparative Example 1B.

Further, a filter medium of Example <NUM>, in another manufacture lot, was manually pulverized with a mortar as a filter medium of Example 1B. The filter medium of Example 1B includes a <NUM> (<NUM> mesh) on product and has a particle size from <NUM> to <NUM>. Further, a filter medium of a simultaneously obtained <NUM> (<NUM> mesh) pass product was taken as Reference Example <NUM>. By measuring a specific surface area and a fine pore volume, results shown in Table <NUM> were obtained. Still further, activated carbons were taken out of commercially available water cleaners and activated carbons having a particle size from <NUM> to <NUM> were sampled, and these were evaluated as Comparative Example 1C and Comparative Example 1D.

Further, <NUM> of each of specimens of Example 1B, Reference Example <NUM>, Comparative Example 1C and Comparative Example 1D was charged in a cartridge, an aqueous solution of Methylene blue was flowed to the cartridge at a flow rate of <NUM>/minute, and a concentration of Methylene blue of water flowed out of the cartridge was measured. Results thereof are shown in <FIG>. In <FIG>, a vertical axis shows an adsorption rate (removal rate) of Methylene blue, which is a value obtained by normalizing with an adsorption amount (removal rate) of a filter medium of Reference Example <NUM> set to <NUM>%. Further, a horizontal axis shows a flow rate of an aqueous solution of Methylene blue. It is obvious also from <FIG> that Methylene blue adsorption amounts of filter media of Example 1B (shown with square) and Reference Example <NUM> (shown with rhombus) are remarkably larger than that of Comparative Example 1C (shown with triangle) or Comparative Example 1D (shown with circle).

A sectional view of a water cleaner of Example <NUM> is shown in <FIG>. The water cleaner of Example <NUM> is a continuous water cleaner and a faucet-coupled water cleaner where a water cleaner body is directly attached to an tip part of a water faucet. The water cleaner of Example <NUM> includes a water cleaner body <NUM>, a first packing part <NUM> that is disposed inside the water cleaner body <NUM> and in which a porous carbon material <NUM> of Example 1A or Example 1B, or Reference Example <NUM> is packed, and a second packing part <NUM> in which cotton <NUM> is packed. Tap water discharged from a water faucet passes from an inlet <NUM> disposed to the water cleaner body <NUM> through a porous carbon material <NUM> and cotton <NUM> and is discharged from an outlet <NUM> disposed to the water cleaner body <NUM>.

A schematic diagram showing a sectional structure of a decontamination sheet member of Example <NUM> is shown in <FIG>. The decontamination sheet member of Example <NUM> includes a porous carbon material of Example 1A or Example 1B, or Reference Example <NUM>, and, a support member. Specifically, the decontamination sheet member of Example <NUM> has a structure where between a support member (nonwoven fabric <NUM>) and another support member (nonwoven fabric <NUM>), which are composed of cellulose, a sheet-like porous carbon material, that is, a carbon/polymer composite <NUM> is sandwiched. The carbon/polymer composite <NUM> includes a porous carbon material of Example 1A or Example 1B, or Reference Example <NUM>, and a binder, and the binder includes, for example, carboxy nitrocellulose. A decontamination sheet member can be formed also by coating a porous carbon material of Example 1A or Example 1B, or, Reference Example <NUM> on a support member, or by blending a porous carbon material of Example <NUM> in a support member.

Example <NUM> is modification of Example <NUM>. In Example <NUM>, an evaluation test of a removal rate of chlorine was conducted.

In manufacture of a porous carbon material in Example <NUM>, a plant-derived material was carbonized at <NUM> to <NUM> and, after that, by treating with an acid or an alkali, a porous carbon material was obtained. That is, firstly, husks of rice were heated (pre-carbonizing treatment) in an inert gas atmosphere. Specifically, husks of rice were carbonized by heating at <NUM> for <NUM> hours in a nitrogen gas flow to obtain a carbide. When such a treatment is applied, a tar component to be generated in the following carbonizing treatment can be reduced or removed. Thereafter, <NUM> of the carbide was charged in an alumina crucible and heated up to <NUM> at a rate of temperature increase of <NUM>/min in a nitrogen gas flow (<NUM>/min). Then, after carbonizing at <NUM> for <NUM> hour to convert to a carbonaceous substance (porous carbon material precursor), the carbonaceous substance was cooled to room temperature. During carbonizing and cooling, a nitrogen gas was continued to flow. Next, the porous carbon material precursor was treated with an acid by dipping in an aqueous solution of <NUM>% by volume of hydrofluoric acid overnight, and, after that, the resultant was washed using water and ethyl alcohol until pH7 was obtained. Then, after drying at <NUM>, by activating by heating at <NUM> for <NUM> hours in a water vapor (<NUM>/min), a porous carbon material of Example <NUM> was obtained.

By measuring a specific surface area and a volume of fine pores of a filter medium in Example <NUM>, results shown in Table <NUM> were obtained. By pulverizing a filter medium of Example <NUM> to control a particle size, a <NUM> (<NUM> mesh) on product was obtained. Example 2A and Example 2B having two kinds of particle size distributions were prepared. Measurement results of particle size distribution with a sieve are shown in Table <NUM>. Further, activated carbons were taken out of commercially available water cleaners, and these were evaluated as Comparative Example 2A, Comparative Example 2B and Comparative Example 2C. Further, masses (unit: gram) when the respective specimens were packed in first packing parts <NUM> having the same volume are shown in Table <NUM>. A packing ratio when each of the specimens is packed in the first packing part <NUM> is called as "packing rate" in some cases. Further, volume ratios of a total of volumes of fine pores having a pore diameter in the range of <NUM> to <NUM> with respect to a total of volumes of fine pores (sum total of volumes of all fine pores) having a diameter of <NUM> × <NUM>-<NUM> m to <NUM> × <NUM>-<NUM> m based on the NLDFT method are shown in Table <NUM>. Still further, measurement results by mercury porosimetry are shown below. Further, measurement results of residue on ignition (ash residue) remained when specimens dried at <NUM> for <NUM> hours were heated up to <NUM> under dry air of <NUM>/min based on a thermogravimetric method (TG) are shown below. Measurement results of the residue on ignition (ash residue) in porous carbon materials of Example <NUM> and Example <NUM>, and measurement results of the residue on ignition (ash residue) in porous carbon material precursors before acid treatment are also shown together.

In the test, a glass tube having an inner diameter of <NUM> was packed with each of specimens having a volume of <NUM>, and water having a chlorine concentration of <NUM>/L was flowed into the glass tube at a flow rate of <NUM>/min. Measurement results of chlorine removal rate obtained based on a method that <MAT> are shown in <FIG>. A flow rate of <NUM>/min is as follows, in terms of spatial velocity (SV).

From <FIG>, it is found that filter media made of porous carbon materials of Example 2A and Example 2B have chlorine removal rates remarkably higher than those of Comparative Example 2A, Comparative Example 2B, and Comparative Example 2C.

Also Example <NUM> is a modification of Example <NUM>. In Example <NUM>, evaluation tests of a removal rate of chlorine, a removal rate of <NUM>,<NUM>,<NUM>-trichloroethane, and a removal rate of <NUM>-chloro-<NUM>,<NUM>-bisethylamino-<NUM>,<NUM>,<NUM>-triazine (CAT) were conducted. A removal rate was calculated from the following formula by gas chromatography. As a porous carbon material that forms a filter medium of Example <NUM>, a porous carbon material (<NUM> (<NUM> mesh) on product) of Example 2A was used. As Comparative Example <NUM>, a filter medium the same as that of Comparative Example 2C was used.

With filter media of Example <NUM> and Comparative Example <NUM>, glass tubes having an inner diameter of <NUM> were packed with each of specimens having a volume of <NUM>, and each of water having a chlorine concentration of <NUM>/L, an aqueous solution of <NUM>,<NUM>,<NUM>-trichloroethane of a concentration of <NUM>/L, and an aqueous solution of CAT of a concentration of <NUM>/L was flowed at a flow rate of <NUM>/min into a glass tube. Removal rates of chlorine, <NUM>,<NUM>,<NUM>-trichloroethane, and CAT are shown in (A), (B) and (C) of <FIG>. From (A), (B) and (C) of <FIG>, it was found that a filter medium formed of a porous carbon material of Example <NUM> has a removal rate remarkably higher than that of Comparative Example <NUM>. A flow rate of <NUM>/min is as follows, in terms of spatial velocity (SV).

In eutrophicated lakes and ponds, mainly in summer, in some cases, blue algae (microcystis and the like) extraordinarily propagate to form a thick layer as if a water surface has a green bloom. This is called as blue-green algae. The blue algae are known to generate toxins harmful to a human body. Among many toxins, a toxin called microcystin LR is particularly alarming. When microcystin LR enters a living body, a liver is largely damaged. Its toxicity is reported in an experiment with mice. Toxic blue green algae that generate microcystin LR propagate in lakes in Australia, Europe and USA and in various places in Asia. In lakes in China, in which a damage is large, blue-green algae that have drastically increased in lakes do not disappear all year long. Since the lakes are used for drinkable water and agricultural water, toxins generated by the blue-green algae in lakes are problematic also in ensuring human drinkable water, and it is strongly demanded that the problem is solved.

In Example <NUM>, adsorption of microcystin LR (number average molecular weight: <NUM>) was evaluated. A porous carbon material that forms a filter medium of Example <NUM> was obtained according to a method roughly the same as that described in Example <NUM>. Specifically, in Example <NUM>, an activation treatment was conducted by heating at <NUM> for <NUM> hours in a water vapor flow (<NUM>/min). Except this point, a method the same as that described in Example <NUM> was used for obtaining the porous carbon material. A specific surface area and a volume of fine pores of a filter medium in Example <NUM> were measured, and results shown in Table <NUM> were obtained. A volume ratio of a total of volumes of fine pores having a pore diameter in the range of <NUM> to <NUM> with respect to a total of volumes of fine pores (volume A, sum total of volumes of all fine pores) having a diameter of <NUM> × <NUM> ° m to <NUM> × <NUM>-<NUM> m based on the NLDFT method is shown in Table <NUM>. A filter medium in Example <NUM> is a <NUM> (<NUM> mesh) pass and <NUM> (<NUM> mesh) on product. Further, as Comparative Example <NUM>, particulate activated carbon (<NUM> (<NUM> mesh) pass and <NUM> (<NUM> mesh) on product) manufactured by Wako Pure Chemical Industries Ltd.

Microcystin concentrations of solutions of filter media of Example <NUM> and Comparative Example <NUM> were obtained before and after the reaction by colorimetry with a UV/visible spectrophotometer, and removal rates thereof were calculated. Results thereof are shown in <FIG>. It was found that a filter medium formed of a porous carbon material of Example <NUM> has a removal rate remarkably higher than that of Comparative Example <NUM>.

In Example <NUM>, particle size dependency was evaluated. As a porous carbon material that forms a filter medium of Example <NUM>, a porous carbon material (<NUM> (<NUM> mesh) pass and <NUM> (<NUM> mesh) on product) in Example <NUM> was used. Further, a <NUM> (<NUM> mesh) pass product of the porous carbon material of Example <NUM> was used as Reference Example <NUM>. Still further, as Comparative Example 5A, particulate activated carbon (<NUM> (<NUM> mesh) pass and <NUM> (<NUM> mesh) on product) was used, and as Comparative Example 5B, a <NUM> (<NUM> mesh) pass product obtained by pulverizing the particulate activated carbon of Comparative Example <NUM> was used.

By using each of filter media of Example <NUM>, Reference Example <NUM>, Comparative Example 5A and Comparative Example 5B as a specimen, <NUM> of the specimen and <NUM> of indole solution (<NUM> × <NUM>-<NUM> mol/L) were charged in a <NUM> screw tube, and, based on a method of quantifying an indole adsorption amount after <NUM> hour, particle size dependency was evaluated. Results thereof are shown in <FIG>. It was found that filter media formed of porous carbon materials of Example <NUM> and Reference Example <NUM> are free from particle size dependency compared with those of Comparative Example 5A and Comparative Example 5B.

The existing activated carbons obtained from a coconut shell or petroleum pitch as a raw material are used in a filter member for water purification, and also in functional foods, cosmetics. However, these activated carbons contain less mineral components and are not suitable for controlling a releasing amount of minerals into water.

Example <NUM> relates to filter. A filter medium of Example <NUM> includes a porous carbon material having a value of a specific surface area by the nitrogen BET method of <NUM> × <NUM><NUM> m<NUM>/g or more, a volume of fine pores by the BHJ method of <NUM><NUM>/g or more, and having a plant containing at least one kind of component selected from the group consisting of sodium, magnesium, potassium and calcium as a raw material. Alternatively, a filter medium of Example <NUM> includes a porous carbon material having a value of a specific surface area by the nitrogen BET method of <NUM> × <NUM><NUM> m<NUM>/g or more, a total of volumes of fine pores having a diameter of <NUM> × <NUM>-<NUM> to <NUM> × <NUM>-<NUM> m obtained by a non-localized density functional theory method of <NUM><NUM>/g or more, desirably <NUM><NUM>/g or more, and having a plant containing at least one kind of component selected from the group consisting of sodium, magnesium, potassium and calcium as a raw material. Or a filter medium of Example <NUM> includes a porous carbon material having a value of a specific surface area by the nitrogen BET method of <NUM> × <NUM><NUM> m<NUM>/g or more, having at least one peak in the range of <NUM> to <NUM>, in a pore diameter distribution obtained by a non-localized density functional theory method, in which a ratio of a total of volumes of fine pores having pore diameters in the range of <NUM> to <NUM>, with respect to a sum total of volumes of all fine pores, is <NUM> or more, and having a plant containing at least one kind of component selected from the group consisting of sodium, magnesium, potassium and calcium as a raw material. Alternatively, a filter medium of Example <NUM> includes a porous carbon material having a value of a specific surface area by the nitrogen BET method of <NUM> × <NUM><NUM> m<NUM>/g or more, a volume of fine pores by mercury porosimetry of <NUM><NUM>/g or more, and having a plant containing at least one kind of component selected from the group consisting of sodium, magnesium, potassium and calcium as a raw material.

In Example <NUM>, a porous carbon material includes a plant containing at least one kind of component selected from the group consisting of sodium (Na), magnesium (Mg), potassium (K) and calcium (Ca) as a raw material. When a filter medium obtained from such a plant raw material is used, since an abundant amount of mineral components is eluted from the porous carbon material into filtrate water, water hardness can be controlled. In this case, when <NUM> of a filter medium is added in <NUM> of water (water for test) having the hardness of <NUM> or less and is allowed to stand for <NUM> hours, the hardness becomes <NUM> or more.

More specifically, in Example <NUM>, skins of citrus fruits such as a mandarin orange skin (Example 6A), an orange skin (Example 6B), and a grape fruit skin (Example 6C), and a skin of a banana (Example 6D) were used as a raw material. Further, Kuraray Coal GW manufactured by Kuraray Chemical Co. was used as Comparative Example <NUM>.

When a porous carbon material making up a filter medium of Example <NUM> was manufactured, the various kinds of plant raw materials were dried at <NUM> for <NUM> hours. Thereafter, a pre-carbonizing treatment was conducted at <NUM> in a nitrogen gas flow for <NUM> hours. Then, after heating at <NUM> for <NUM> hour, the products were cooled to room temperature and pulverized with a mortar. Thus-obtained specimens (carbonaceous material, porous carbon material precursor) are referred to as specimens of Example 6a, Example 6b, Example 6c and Example 6d, for convenience. Thereafter, the respective specimens were dipped in concentrated hydrochloric acid for <NUM> hours, followed by washing until a wash solution became neutral. Thus, specimens of Example 6a', Example 6b', Example 6c' and Example 6d' were obtained. Next, by activating the specimens of Example 6a', Example 6b', Example 6c' and Example 6d' at <NUM> in water vapor flow for <NUM> hour, filter media including porous carbon materials of Example 6A, Example 6B, Example 6C and Example 6D could be obtained.

Composition analysis results of specimens of Example 6A, Example 6B, Example 6C and Example 6D and of a specimen of Comparative Example <NUM> are shown in Table <NUM> below. Further, results of X-ray diffractometry of specimens of Example 6a, Example 6b, Example 6c and Example 6d and porous carbon materials of Example 6a', Example 6b', Example 6c' and Example 6d' are shown in (A) to (D) of <FIG>. Filter media of Example 6A, Example 6B, Example 6C and Example 6D all were <NUM> mesh pass products. Further, when a specific surface area and a pore volume were measured, results shown in Table <NUM> and (A) and (B) of <FIG> were obtained. Further, volume ratios of a total of volumes of fine pores having a pore diameter in the range of <NUM> to <NUM> with respect to a total of volumes of fine pores having a diameter of <NUM> × <NUM>-<NUM> to <NUM> × <NUM>-<NUM> m (volume A, sum total of volumes of all fine pores) based on the NLDFT method are shown in Table <NUM>. Further, a graph showing measurement results of pore diameter distribution obtained by the non-localized density functional theory method of filter media of Example 6A, Example 6B, Example 6C and Example 6D, and Comparative Example <NUM> is shown in <FIG>.

From Table <NUM>, it was found that specimens of Example 6A, Example 6B, Example 6C and Example 6D contain mineral components more abundant than a specimen of Comparative Example <NUM>. Further, from results of X-ray diffractometry, crystalline peaks derived from the mineral components that were found in specimens of Example 6a, Example 6b, Example 6c and Example 6d were not observed from filter media of Example 6a', Example 6b', Example 6c' and Example 6d'. From this, it is considered that although a mineral content is partially removed once by acid treatment with concentrated hydrochloric acid, by an activation treatment, a mineral content inside the filter medium becomes prominent again.

Each of specimens of Example 6A, Example 6B, Example 6C and Example 6D and a specimen of Comparative Example <NUM> was added at a rate of <NUM>/<NUM> to test water (hardness: <<NUM>) that is pure water, and after stirring for <NUM> hours, the resulting solution was filtrated, and amounts of various kinds of minerals contained in the obtained filtrate were quantified by ICP-AES. In Table <NUM>, mineral amounts in filtrates obtained from each of specimens and hardness of the filtrates are shown. Here, the hardness (mg/L) was calculated as that calcium concentration (mg/L) × <NUM> + magnesium concentration (mg/L) × <NUM>. For reference, also classification of water according to standard of World Health Organization (WHO) (soft water: <NUM> or more and less than <NUM>, medium-level soft water (medium hard water): <NUM> or more and less than <NUM>, hard water: <NUM> or more and less than <NUM>, very hard water: <NUM> or more) is shown.

From Table <NUM>, in each of specimens of Example <NUM>, mineral eluting characteristics higher than that of Comparative Example <NUM> could be confirmed, and it was shown that porous carbon materials of Example <NUM> are suitable for controlling the hardness of a filtrate. Further, it was found that, depending on plant raw materials used, the hardness of the filtrate could be controlled to soft water, to medium hard water, to hard water, and to very hard water.

Example <NUM> relates to filter media. Example <NUM> intends to remove dodecylbenzene sulfonate (specifically, straight chain sodium dodecylbenzene sulfonate) of a synthetic detergent component that is abundantly discharged in a water environment, an agricultural germicide chlorothalonil (TPN, C<NUM>Cl<NUM>N) and a pesticide dichlorvos (DDVP, C<NUM>H<NUM>Cl<NUM>O<NUM>P), which are abundantly used, soluble lead eluted from water pipes, free residual chlorine that is a typical contaminant in tap water, and various organic halogen compounds byproduced during disinfection by chlorine (including organic halogen compounds generated from a humic substance).

In Example <NUM>, a porous carbon material was manufactured according to the following method. Further, as Comparative Example <NUM>, Kuraray Coal GW was used.

In the manufacture of a porous carbon material in Example <NUM>, after a plant-derived material was carbonized at <NUM> to <NUM>, by treating with an alkali, a porous carbon material was obtained. That is, firstly, rice husks were heated (preliminary carbonizing treatment) in an inert gas flow. Specifically, by heating rice husks in a nitrogen gas flow at <NUM> for <NUM> hours to carbonize, a carbide was obtained. When such a treatment is conducted, a tar component to be generated in the following carbonization can be reduced or removed. Thereafter, <NUM> of the carbide was charged in an alumina crucible and heated up to <NUM> at a rate of temperature increase of <NUM>/min in a nitrogen gas flow (<NUM>/min). Then, after carbonizing at <NUM> for <NUM> hour to convert to a carbonaceous substance (porous carbon material precursor), the carbonaceous substance was cooled to room temperature. During carbonizing and cooling, a nitrogen gas was continued to flow. Next, the porous carbon material precursor was treated at <NUM> with an alkali by dipping in an aqueous solution of <NUM>% by mass of sodium hydroxide overnight, and, after that, the resultant was washed using water and ethyl alcohol until pH7 was obtained. Then, after drying at <NUM>, by activating by heating at <NUM> for <NUM> hours in a water vapor flow (<NUM>/min), a porous carbon material of Example <NUM> was obtained.

Results of measurements of particle size distributions of specimens of Example <NUM> and Comparative Example <NUM> are shown in Table <NUM>. Further, results of measurement of specific surface areas and pore volumes of specimens of Example <NUM> and Comparative Example <NUM> are shown in the following Tables <NUM> and <NUM>. Measurement items and units in Tables <NUM> and <NUM> are the same as those in Tables <NUM> and <NUM>. Further, measurement results by mercury porosimetry are shown in Table <NUM>.

From each of specimens of Example <NUM> and Comparative Example <NUM>, <NUM><NUM> thereof was sampled and housed in a column with a stainless net. Then, a solution in which.

respectively were dissolved in <NUM> of water was prepared, and, the solution was flowed past through <NUM><NUM> of each of specimens at a flow rate of <NUM>/min. After that, concentrations thereof before and after water passing were measured, and the removal rates were calculated. A flow rate of <NUM>/min corresponds to the following spatial velocity (SV).

Next, the removal rate of sodium dodecylbenzene sulfonate was measured based on cell-atomic absorption spectrometry, the removal rates of chlorothalonil and dichlorvos were measured based on gas chromatography with an electron capture detector (ECO-GC), the removal rate of soluble lead was measured based on inductively-coupled plasma mass spectrometry (ICP/MS), the removal rate of free chlorine was measured based on cell-atomic absorption spectrometry, and the removal rate of total organic halogens was measured based on ion chromatography.

Measurement results of removal rate of sodium dodecylbenzene sulfonate (DBS) are shown in (A) and (B) of <FIG>, measurement results of removal rate of chlorothalonil (TPN) are shown in (A) and (B) of <FIG>, measurement results of removal rate of dichlorvos (DDVP) are shown in <FIG>, measurement results of removal rate of soluble lead are shown in <FIG>, measurement results of removal rate of free chlorine are shown in (A) and (B) of <FIG>, and measurement results of removal rate of total organic halogens are shown in <FIG>. In all of these, Example <NUM> showed the removal rates higher than those of Comparative Example <NUM>.

That is, in a filter medium of Example <NUM>, when water containing <NUM>µg/L of a substance having a molecular weight of <NUM> × <NUM><NUM> to <NUM> × <NUM><NUM> was continuously flowed at the spatial velocity of <NUM> hr-<NUM> for <NUM> hours, the time taken until the removal rate of the substance reached <NUM>% was twice or more longer than the time taken until the removal rate of the substance reached <NUM>% when a coconut shell activated carbon was used.

Further, in a filter medium of Example <NUM>, when water containing <NUM>/L of dodecylbenzene sulfonate was continuously flowed at the spatial velocity of <NUM> hr-<NUM> for <NUM> hours, the removal rate of dodecylbenzene sulfonate was <NUM>% or more.

Still further, in a filter medium of Example <NUM>, when water containing <NUM>µg/L of chlorothalonil was continuously flowed at the spatial velocity of <NUM> hr-<NUM> for <NUM> hours, the removal rate of chlorothalonil was <NUM>% or more.

Further, in a filter medium of Example <NUM>, when water containing <NUM>µg/L of dichlorvos was continuously flowed at the spatial velocity of <NUM> hr-<NUM> for <NUM> hours, the removal rate of dichlorvos was <NUM>% or more.

Still further, in a filter medium of Example <NUM>, when water containing <NUM>µg/L of soluble lead was continuously flowed at the spatial velocity of <NUM> hr-<NUM> for <NUM> hours, the removal rate of soluble lead was <NUM>% or more.

Further, in a filter medium of Example <NUM>, when water containing <NUM>/L of free chlorine was continuously flowed at the spatial velocity of <NUM> hr-<NUM> for <NUM> hours, the removal rate of free chlorine was <NUM>% or more.

Still further, in a filter medium of Example <NUM>, when water containing <NUM>µg/L in terms of chlorine of total organic halogens was continuously flowed at the spatial velocity of <NUM> hr-<NUM> for <NUM> hours, the removal rate of total organic halogens was <NUM>% or more.

From the measurement results of the removal rate of sodium dodecylbenzene sulfonate (DBS), it was found that the filter medium of Example <NUM>, in spite of the packing rate of only about <NUM>% compared with that of the activated carbon of Comparative Example <NUM>, maintained the removal rate higher than that of the activated carbon of Comparative Example <NUM>, that is, at about <NUM> hours of water passing time, the removal rate was <NUM>%, and, at about <NUM> hours of water passing time, the removal rate was <NUM>% or more, at the SV = <NUM> hr-<NUM>. On the other hand, in the activated carbon of Comparative Example <NUM>, immediate after water passing, the removal rate rapidly decreased. This is considered that it is because with the activated carbon of Comparative Example <NUM>, which has only small fine pores, adsorption rate of DBS that has a large molecular weight is low. From results of tests, in Example <NUM>, by using a stationary water cleaner (hereinafter, referred to as "stationary water cleaner-A" for convenience) that contains <NUM> of a filter medium of Example <NUM>, when assumed that water containing <NUM>/L of DBS is filtered by <NUM> liters a day at the flow rate of <NUM>/min, it was inferred that <NUM>% of DBS can be removed, for about <NUM> months. Further, also at the SV = <NUM> hr-<NUM>, the removal rate higher than that of Comparative Example <NUM> could be maintained. Then, when assumed that water containing <NUM>/L of DBS is filtered by <NUM> liters per day at the flow rate of <NUM>/min, it was inferred that <NUM>% or more of DBS can be removed, with the use of a stationary water cleaner (hereinafter, referred to as "stationary water cleaner-B" for convenience) that contains <NUM> of a filer medium of Example <NUM>, for about <NUM> months.

From measurement results of removal rate of chlorothalonil (TPN), at the SV = <NUM> hr-<NUM>, a filter medium of Example <NUM> maintained the removal rate of TPN higher than that of the activated carbon of Comparative Example <NUM>, that is, the removal rate of the filter medium of Example <NUM> maintained the removal rate of <NUM>% or more up to about <NUM> hours, which is about <NUM> times a value of the activated carbon of Comparative Example <NUM> at the water passing time of <NUM> hours. This is considered that since a molecular weight of TPN is as large as <NUM>, a filter medium of Example <NUM> that has a larger adsorption speed is more advantageous than the activated carbon of Comparative Example <NUM>. Further, since TPN has smaller solubility in water and higher adsorptivity, a high removal rate could be maintained for a long time. And, from results of tests, in Example <NUM>, when assumed that water containing <NUM>µg/L of TPN is filtered by <NUM> per day at the flow rate of <NUM>/min by using the stationary water cleaner-A, it was inferred that <NUM>% or more of TPN can be removed, for about <NUM> year. On the other hand, at the SV = <NUM> hr-<NUM>, although the removal rate is lower than that in the case of the SV = <NUM> hr-<NUM>, when assumed that water containing <NUM>µg/L of TPN is filtered by <NUM> per day at the flow rate of <NUM>/min, it was inferred that <NUM>% or more of TPN can be removed, with the use of the stationary water cleaner-B, for about <NUM> months.

Further, from measurement results of removal rate of dichlorvos (DDVP), at the SV = <NUM> hr-<NUM>, a filter medium of Example <NUM> maintained the removal rate higher than that of the activated carbon of Comparative Example <NUM>, that is, the removal rate of the filter medium of Example <NUM> maintained the removal rate of <NUM>% or more up to about <NUM> hours of water passing time. This is considered that since a molecular weight of DDVP is slightly large such as the molecular weight of <NUM>, a filter medium of Example <NUM> that has a larger adsorption speed is more advantageous than the activated carbon of Comparative Example <NUM>. Since DDVP has a very large solubility in water such as <NUM>/L and an equilibrium adsorption amount is small, the removal rate up to <NUM> hours of water passing time was <NUM>% or more. However, after that, at about <NUM> hours of the water passing time, the removal rate became <NUM>%. About <NUM> hours of the water passing time corresponds to about <NUM> months use when assumed that water containing <NUM>µg/L of DDVP is filtered <NUM> liters per day at the flow rate of <NUM>/min by using the stationary water cleaner-A, and about <NUM> hours of the water passing time corresponds to about <NUM> months use.

From measurement results of removal rate of soluble lead, at the SV = <NUM> hr-<NUM>, a filter medium of Example <NUM> maintained the removal rate higher than that of the activated carbon of Comparative Example <NUM>, and, the removal rate at about <NUM> hours of water passing time was <NUM>% or more. The removal rate of the activated carbon of Comparative Example <NUM> was <NUM>% or less at about <NUM> hours of the water passing time. This is considered to be showing that a filter medium of Example <NUM> has many active points that are liable to adsorb lead. And, from results of tests, when assumed that water containing <NUM>µg/L of soluble lead (in terms of lead) is filtered by <NUM> liters per day at the flow rate of <NUM>/min by using the stationary water cleaner-A, it was inferred that <NUM>% or more of lead can be removed, for about <NUM> months.

From measurement results of removal rate of free chlorine, at the SV = <NUM> hr-<NUM>, a filter medium of Example <NUM> maintained the removal rate higher than that of Comparative Example <NUM>, and, the removal rate even after about <NUM> hours of water passing time was about <NUM>%. Since the free chlorine is removed by a reduction reaction on a surface of the filter medium, it is inferred that a filter medium of Example <NUM> has not only a large intraparticle diffusion speed but also many active points that are liable to reduce free chlorine on a surface. And, from results of tests, when assumed that water containing <NUM>/L of free chlorine (in terms of chlorine) is filtered by <NUM> liters per day at the flow rate of <NUM>/min by using the stationary water cleaner-A, it was inferred that <NUM>% or more of free chlorine can be removed, for about <NUM> year. On the other hand, even at the SV = <NUM> hr-<NUM>, the removal rate after <NUM> hours of water passing time is about <NUM>%. And, from results of tests, when assuming that water containing <NUM>/L of free chlorine (in terms of chlorine) is filtered by <NUM> liters per day at the flow rate of <NUM>/min by using the stationary water cleaner-B,, it was inferred that <NUM>% or more of free chlorine can be removed, for about <NUM> year.

From measurement results of removal rate of total organic halogens (including organic halogen compounds generated from a humic substance), at the SV = <NUM> hr-<NUM>, a filter medium of Example <NUM> maintained the removal rate higher than that of the activated carbon of Comparative Example <NUM> up to <NUM> hours of the water passing time. Since, among the TOX components, a substance having a slightly larger molecular weight is contained, it is considered that a filter medium of Example <NUM>, which has a larger adsorption speed, has the removal rate larger than that of the activated carbon of Comparative Example <NUM>. And, from results of tests, when assuming that water containing <NUM>µg/L (in terms of chlorine) of total organic halogens (TOX) is filtered by <NUM> liters per day at the flow rate of <NUM>/min by using the stationary water cleaner-A, it was inferred that <NUM>% or more can be removed, for about <NUM> months.

Example <NUM> is a modification of Example <NUM> to Example <NUM> (Examples <NUM> and <NUM> do not contain a decontaminant produced according to the method of the present invention). In Example <NUM>, as a schematic partial sectional view is shown in (A) of <FIG>, each of filter media described in Examples <NUM> to <NUM> was assembled in a bottle (so-called PET bottle) <NUM> with a cap member <NUM>. Specifically, inside the cap member <NUM>, a filter medium <NUM> of any of Examples <NUM> to <NUM> was disposed and filters <NUM> and <NUM> were disposed on a liquid inlet side and a liquid outlet side of the cap member <NUM> to prevent the filter medium <NUM> from eluting off. Then, when a liquid or water (drinkable water, a lotion, or the like) <NUM> in the bottle <NUM> is drunk or used by passing through the filter medium <NUM> disposed inside the cap member <NUM>, for example, mineral components in the liquid (water) can be increased. The cap member <NUM> is usually closed with a cap (not shown).

Or, as a schematic sectional view is shown in (B) of <FIG>, a form in which a filter medium <NUM> of any of Examples <NUM> to <NUM> is housed in a permeable bag <NUM> and the bag <NUM> is put into a liquid or water (drinkable water, a lotion, or the like) <NUM> in a bottle <NUM> can be adopted. A reference numeral <NUM> denotes a cap for closing an opening of the bottle <NUM>. Or, as a schematic sectional view is shown in (A) of <FIG>, a filter medium <NUM> of any of Examples <NUM> to <NUM> is disposed inside a straw member <NUM> and a filter (not shown) is disposed on a liquid inlet side and a liquid outlet side of the straw member to prevent the filter medium <NUM> from flowing off. Then, when a liquid or water (drinkable water) <NUM> in the bottle <NUM> is drunk by passing through the filter medium <NUM> of Examples <NUM> to <NUM> disposed inside the straw member <NUM>, mineral components in the liquid (water) can be increased. Or, as a partially cutaway schematic diagram is shown in (B) of <FIG>, a filter medium <NUM> of any of Examples <NUM> to <NUM> is disposed inside a spray member <NUM> and a filter (not shown) is disposed on a liquid inlet side and a liquid outlet side of the spray member <NUM> to prevent the filter medium <NUM> from flowing off. Then, by pushing a push button <NUM> provided to the spray member <NUM> to allow a liquid or water (drinkable water, a lotion, or the like) <NUM> inside the bottle <NUM> to pass through the filter medium <NUM> of Examples <NUM> to <NUM> disposed inside the spray member <NUM> to spray from a spray hole <NUM>, mineral components in the liquid (water) can be increased.

In the above, the present invention was described based on preferred examples. However, the present invention is not limited to these examples and can be variously modified. A water cleaner in which as a filter medium, a filter medium described in Example <NUM> and a ceramic filter medium (ceramic filter medium having fine pores) are combined, and a water cleaner in which a filter medium described in Example <NUM> and an ion exchange resin are combined, can be made. Further, a porous carbon material that makes up a filter medium may be granulated to be used.

In Examples, a case where as a raw material of a porous carbon material, rice husks are used was described. However, other plant-derived raw materials may be used. Here, as other plants, for example, straws, reeds, or Wakame stems, vascular plants that live on land, ferns, bryophytes, algae, seaweeds can be mentioned. These materials may be used singularly or in a combination of several kinds thereof. Specifically, by carbonizing, for example, rice straws (for example, the Isehikari produced in Kagoshima) as a plant-derived material, which is a raw material of a porous carbon material, into a carbonaceous substance (porous carbon material precursor), followed by performing an acid treatment, a porous carbon material can be obtained. Alternatively, by carbonizing rice reeds as a plant-derived material, which is a raw material of a porous carbon material, into a carbonaceous substance (porous carbon material precursor), followed by performing an acid treatment, a porous carbon material can be obtained. Further, also in a porous carbon material obtained by treating with, in place of an aqueous solution of hydrofluoric acid, an alkali (base) such as an aqueous solution of sodium hydroxide, the same result could be obtained.

Claim 1:
Method for producing a decontaminant, wherein the method comprises:
providing a plant-derived material containing silicon,
carbonizing the plant-derived material at <NUM> to <NUM> to obtain a porous carbon material precursor,
treating the porous carbon material precursor with an acid or an alkali to obtain a porous carbon material and
performing a gas activation of the porous carbon material by using oxygen, water vapor, carbon dioxide or air as an activator, and heating the porous carbon material under such an atmosphere, at <NUM> to <NUM> for several tens of minutes to several hours,
to obtain a decontaminant in the form of a porous carbon material, wherein
(a) the porous carbon material having a value of a specific surface area based on a nitrogen BET method of <NUM> x <NUM><NUM> m<NUM>/g or more, a volume of fine pores based on a BJH method of <NUM><NUM>/g or more, wherein as a fine pore, a "meso fine pore" having a pore diameter from <NUM> to <NUM>, a "micro fine pore" having a pore diameter smaller than <NUM>, and a "macro fine pore" having a pore diameter exceeding <NUM> are included, and a particle size of <NUM> or more,
(b) the porous carbon material when dried at <NUM> and heated for <NUM> hours up to <NUM> in dry air results in a content of a residue on ignition (ash residue) of <NUM> % by mass or less,
(c) the bulk density of the porous carbon material is <NUM>/cm<NUM> or more and <NUM>/cm<NUM> or less, and
(d) the porous carbon material has at least one peak in the range of <NUM> to <NUM>, in a pore diameter distribution of a non-localized density functional theory method as specified in JISZ8831-<NUM>:<NUM>, in which a ratio of a total of volumes of fine pores that have diameters in the range of <NUM> to <NUM>, with respect to a sum total of volumes of all fines pores, is <NUM> or more.