Activated carbon adsorbent

Abstract

The present invention aims to provide an activated carbon adsorbent that can maintain a high level of adsorption performance for low-molecular-weight compounds even when both low-molecular-weight and high-molecular-weight compounds coexist. The solution involves achieving a pore diameter peak (Wp) of 0.52–0.70 nm based on the pore volume calculated using the GCMC method for CO2 adsorption; a pore volume (VSN) of 0.45–0.55 cm³ / g for sub-nanopores with a pore diameter of less than 1.0 nm calculated using the aforementioned GCMC method; a pore volume (VME) of 0.01–1.00 cm³ / g for pore diameters of 3–50 nm calculated using the DH method for N2 adsorption; and an average pore diameter of 1.7–5.0 nm measured using the BET method.

Description

Activated carbon adsorbent This invention relates to an activated carbon adsorbent with excellent adsorption performance for toxic substances. Kidney or liver disease is widely known to cause uremia or encephalopathy such as altered consciousness due to the accumulation of toxic substances in the blood. As a treatment for mild kidney or liver disease, some researchers have developed oral adsorbents that utilize the adsorption properties of activated carbon. These activated carbon adsorbents are designed to selectively adsorb substances that should be removed, such as uremic toxins, while minimizing the adsorption of beneficial substances like enzymes in the body. Generally speaking, since enzymes are high molecular weight compounds with molecular weights of tens of thousands, while toxins are low molecular weight compounds with molecular weights of hundreds, it is believed that in activated carbon adsorbents, high selective adsorption can be achieved by perfecting the micropores that serve as adsorption sites for toxins. Therefore, some have proposed activated carbon adsorbents that combine selective adsorption rate and indole adsorption rate by reducing the volume of mesopores to macropores (for example, see Patent Document 1); and activated carbon adsorbents that reduce the pore volume of mesopores relative to the pore volume of micropores, thereby improving the adsorption performance of harmful substances in the presence of bile acids (for example, see Patent Document 2). Regarding the activated carbon adsorbent in Patent Document 1, the general method for evaluating its adsorption capacity involves contacting toxins and enzymes with activated carbon in individual systems and measuring the adsorption rate of each substance. This is done through adsorption tests of multiple single components, and the adsorption selectivity is evaluated based on the performance of each test. However, it is generally accepted that in the actual in vivo environment, the activated carbon adsorbent is affected by various digestive enzymes and other high-molecular-weight compounds that hinder toxin adsorption before it adsorbs toxins. Therefore, in previous performance evaluations based on single-component adsorption tests, it is difficult to obtain an appropriate assessment of the adsorption phenomena in the in vivo environment where digestive enzymes and other substances are present. Furthermore, the activated carbon adsorbent in Patent Document 2 uses a method to evaluate the adsorption performance of toxic substances based on an experiment in which indole is adsorbed in the presence of a large amount of bile acids contained in bile. However, since the molecular weight of bile acids coexisting with indole is extremely small compared to high molecular weight compounds such as digestive enzymes, it is difficult to properly evaluate the adsorption phenomenon in the presence of digestive enzymes and other high molecular weight compounds in the body. Therefore, the inventors of this case, envisioning its use in the in vivo environment where digestive enzymes and other substances exist, have diligently conducted repeated research, ultimately inventing an activated carbon adsorbent that can maintain a high level of adsorption performance for low-molecular-weight compounds even when both low-molecular-weight compounds, which are equivalent to toxic substances, and high-molecular-weight compounds, which may hinder the adsorption of toxins, coexist. [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Patent No. 6386571 [Patent Document 2] Japanese Patent No. 6306721 [The problem that the invention aims to solve] This invention is proposed in view of the above-mentioned circumstances, and provides an activated carbon adsorbent that can maintain the adsorption performance of low-molecular-weight compounds at a high level even when both low-molecular-weight and high-molecular-weight compounds coexist. [Means of Problem Solving] That is, the first invention relates to an activated carbon adsorbent, characterized by: based on CO The peak value (W) of the pore diameter based on the pore volume calculated by the GCMC method for adsorption. p The pore size is 0.52–0.70 nm, and the pore volume (V) of sub-nanopores with a pore diameter of less than 1.0 nm, calculated by the aforementioned GCMC method, is... SN The value is 0.45–0.55 cm. 3 / g, based on N 2. The pore volume (V) with a pore diameter of 3–50 nm calculated by the DH method for adsorption. ME The value is 0.01–1.00 cm. 3 / g, the average pore diameter measured by the BET method is 1.7 to 5.0 nm. The second invention relates to the pore volume (V) of the aforementioned sub-nanopores as specified in the first invention, as defined by the following formula (i). SN ) and the aforementioned pore volume (V) with a pore diameter of 3-50 nm ME The volume ratio (V) SN / ME The range is 3 to 50. The third invention relates to the hardness (H) of activated carbon particles with a particle size of 300 μm, calculated from the average hardness of activated carbon particles with a diameter of 150–500 μm in the first or second invention. D300 The range is 2.0 to 30.0 N. The fourth invention relates to the fact that, in the first or second invention, the aforementioned activated carbon adsorbent is a therapeutic or preventative agent for oral administration of nephropathy or hepatopathy. The fifth invention relates to the third invention, where the aforementioned activated carbon adsorbent is used as a therapeutic or preventative agent for orally administered nephropathy or hepatopathy. [Effects of the Invention] According to the activated carbon adsorbent of the first invention, since based on CO The peak value (W) of the pore diameter based on the pore volume calculated by the GCMC method for adsorption. pThe pore size is 0.52–0.70 nm, and the pore volume (V) of sub-nanopores with a pore diameter of less than 1.0 nm, calculated by the aforementioned GCMC method, is... SN The value is 0.45–0.55 cm. 3 / g, based on N 2. The pore volume (V) with a pore diameter of 3–50 nm calculated by the DH method for adsorption. ME The value is 0.01–1.00 cm. 3 / g, the average pore diameter measured by the BET method is 1.7 to 5.0 nm, and it can maintain the adsorption performance of low molecular weight compounds at a high level even when low molecular weight compounds and high molecular weight compounds coexist. According to the activated carbon adsorbent of the second invention, in the first invention, due to the aforementioned micropore volume (V) of the sub-nanopores SN ) and the aforementioned pore volume (V) with a pore diameter of 3-50 nm ME The volume ratio (V) SN / ME The value is 3-50, which can inhibit the decrease in the adsorption performance of toxic substances. According to the activated carbon adsorbent of the third invention, in the first or second invention, the hardness (H) of activated carbon particles with a particle size of 300 μm is calculated from the average hardness of activated carbon particles with a diameter of 150 to 500 μm. D300 The N value is 2.0–30.0 N, which can maintain the shape of activated carbon particles and inhibit the decrease in adsorption performance. According to the fourth invention, the activated carbon adsorbent, in the first or second invention, is a therapeutic or preventative agent for oral administration of nephropathy or hepatopathy, and is highly effective in selectively adsorbing pathogens of nephropathy or hepatopathy, thus making it suitable as a therapeutic or preventative agent. According to the activated carbon adsorbent of the fifth invention, in the third invention, since the aforementioned activated carbon adsorbent is a treatment or preventive agent for oral administration of nephropathy or hepatopathy, it has a high selective adsorption effect on pathogens of nephropathy or hepatopathy, and is therefore suitable as a treatment or preventive agent. [Forms of Invention Implementation] The activated carbon adsorbent of this invention effectively adsorbs low-molecular-weight compounds in an environment where low-molecular-weight compounds and high-molecular-weight compounds coexist. This is achieved through the use of the peak value (W) of the pore diameter. p ), the pore volume (V) of sub-nanopores with a pore diameter of less than 1.0 nm SN ), pore volume (V) with a diameter of 3-50 nm ME Its physical properties are defined by the average pore diameter, where the coexistence environment is assumed to be used in the in vivo environment where digestive enzymes, etc., exist. Activated carbon adsorbents are suitable for oral administration, for example, using activated carbon as an adsorbent and forming tablets with additives as binders. Activated carbon adsorbents as oral medications are particularly useful as treatments or preventative agents for oral nephropathy or hepatopathy. That is, activated carbon adsorbents, due to their high selective adsorption of pathogens causing nephropathy or hepatopathy, can be administered orally to adsorb and retain these pathogens within the pores of their surface and excrete them from the body, thereby inhibiting symptom exacerbation or improving the condition. Furthermore, since activated carbon adsorbents can reduce the concentration of pathogens causing disease or chronic symptoms in the body through pre-oral administration, they are also considered effective as preventative agents to inhibit symptom exacerbation in cases of congenital or acquired metabolic abnormalities or suspected cases of such abnormalities. Kidney diseases include, for example, chronic renal failure, acute renal failure, chronic pyelonephritis, acute pyelonephritis, chronic nephritis, acute nephritis syndrome, acute progressive nephritis syndrome, chronic nephritis syndrome, nephrotic syndrome, nephrosclerosis, interstitial nephritis, tubular disease, lipoid nephropathy, diabetic nephropathy, renovascular hypertension, and hypertension syndrome, as well as secondary kidney disease accompanying these primary diseases or mild renal failure before dialysis. Liver diseases include, for example, fulminant hepatitis, chronic hepatitis, viral hepatitis, alcoholic hepatitis, liver fibrosis, cirrhosis, liver cancer, autoimmune hepatitis, drug-induced liver injury, primary biliary cirrhosis, tremor, encephalopathy, metabolic abnormalities, and functional disorders. The preferred raw material for activated carbon adsorbents is resin carbides, such as phenolic resins. Phenolic resin carbides can enhance activation, increase specific surface area, and improve the ratio (volume ratio) of the sum of mesopore volumes to the sum of micropore volumes, thus more easily improving the adsorption performance of toxic substances. Examples of phenolic resins include phenolic varnish-type or methyl phenolic-type resins, as well as composite phenolic resins. The activated carbon from phenolic resins is preferably made into granules or spheres with an average particle size ranging from 20 to 1000 μm. If the average particle size of the activated carbon is too small, it will be too dense when made into tablets, which may lead to poor disintegration. If the average particle size of the activated carbon is too large, the surface area for contact and bonding between the activated carbon particles will increase due to the additives acting as binders, which will weaken the binding force and may result in lower tablet hardness. Besides phenolic resins, cellulose can also be used as a raw material for activated carbon adsorbents. When using cellulose as a raw material, by creating macroporous activated carbon and using additives to formulate it into tablet form, it has been found that the decrease in adsorption performance caused by activated carbon can be suppressed. The peak of the pore diameter (W) p (Based on CO) The pore volume calculated by the GCMC method for adsorption is the maximum value of the baseline pore diameter. This pore volume (cm²) 3 The pore volume ( / g) is the pore volume of smaller micropores (diameter less than 1.4 nm) calculated by analyzing the carbon dioxide adsorption isotherm at 298 K using GC-MC. The peak of the pore diameter, based on the pore volume, increases in diameter as the activated carbon is activated. A suitable pore diameter peak is 0.52–0.70 nm. If the pore diameter peak is too small, there is a risk of insufficient adsorption of toxic substances. If the pore diameter peak is too large, it indicates over-activation, potentially leading to the adsorption of large molecular weight beneficial substances such as enzymes in biological systems. The pore volume (V) of sub-nanopores with a pore diameter of less than 1.0 nm SN The values ​​were calculated by determining the carbon dioxide adsorption isotherm at 298 K and analyzing it using the GCMC method. The micropore volume of sub-nanopores is an indicator of the adsorption performance of low-molecular-weight compounds of toxic substances. A suitable micropore volume is 0.45–0.55 cm³. 3 / g. If the pore volume of sub-nanopores is too small, there is a risk that the adsorption performance of toxic substances may be insufficient. When the pore volume of sub-nanopores reaches a certain level, the sub-nanopores will associate with each other to form larger micropores of 1 nm or more. Therefore, it is necessary to appropriately regulate their upper limit. The pore volume (V) with a diameter of 3–50 nm ME ) is based on N 2. Values ​​calculated using the Dolimore-Heal (DH) method for adsorption. This pore volume corresponds to the pore volume of mesopores with a pore diameter of 3–50 nm, calculated by analyzing the nitrogen adsorption isotherm at 77 K using the DH method. The pore volume of 3–50 nm corresponds to the pore volume of mesopores containing digestive enzymes and other macromolecular compounds, and is an indicator of the adsorption performance of these macromolecular compounds. A suitable pore volume of 3–50 nm is 0.01–1.00 ml / g, preferably 0.01–0.20 ml / g. If the pore volume of 3–50 nm is too small, the diffusion pathways of toxic substances to the micropores may be blocked due to the influence of various enzymes and other macromolecular compounds present in the body, potentially leading to insufficient adsorption of toxic substances. If the volume of micropores with a diameter of 3 to 50 nm is too large, there is a risk of excessive adsorption of useful substances with large molecular weights, such as enzymes in living organisms. The average pore diameter is the value measured using the BET method. Specifically, assuming the pores are cylindrical, the pore volume (mL / g) is determined by analyzing the pore distribution using the DH and MP methods based on the nitrogen adsorption isotherm at 77 K, and the specific surface area (m²) is determined by analyzing the nitrogen adsorption isotherm at 77 K using the BET method. 2 / g), calculated by the following formula (ii). A suitable average pore diameter is 1.7–5.0 nm, preferably 1.7–2.5 nm. If the average pore diameter is too small, the adsorption capacity for toxic substances may decrease. If the average pore diameter is too large, there is a risk of excessive adsorption of large molecular weight useful substances such as enzymes in living organisms. For the activated carbon adsorbent of the present invention, the pore volume (V) of the sub-nanopores specified by the following formula (i) SN ) and the micropore volume (V) of mesopores with a diameter ranging from 3 to 50 nm. ME The volume ratio (V) SN / ME The optimal value is 3-50. This volume ratio (V) SN / ME Volume ratio (V1) is the ratio of the pore volume of sub-nanopores targeting low-molecular-weight compounds to the pore volume of mesopores with a diameter of 3–50 nm targeting high-molecular-weight compounds. A value of 3–50 indicates that the pore volume targeting low-molecular-weight compounds is greater than that targeting high-molecular-weight compounds. This helps to suppress the decrease in adsorption performance for toxic substances when both types of compounds coexist. SN / MEIf the volume ratio is too small, the pore volume for adsorbing low-molecular-weight compounds may be insufficient, potentially leading to reduced adsorption performance. (Volume ratio) SN / ME If the pore size is too large, the volume of the mesopores, which serve as diffusion pathways for toxic substances, will be insufficient, which may hinder the adsorption of toxic substances and reduce the adsorption performance of toxic substances. Furthermore, by satisfying the above-mentioned range in terms of volume ratio, the excessive adsorption of polymers in the presence of both low-molecular-weight and high-molecular-weight compounds can be suppressed. In particular, if the volume ratio is too small, the pore volume targeting polymers becomes too large, which may lead to excessive adsorption of polymers and is therefore undesirable. Furthermore, the activated carbon adsorbent of the present invention has a hardness (H) of 300 μm activated carbon particles calculated from the average hardness of activated carbon particles with a diameter of 150–500 μm. D300 The preferred hardness is 2.0–30.0 N. The average hardness is generally calculated based on the average compressive strength of any particle among activated carbon particles with a diameter of 150–500 μm in orally administered activated carbon adsorbents. In particular, to suppress hardness inhomogeneity caused by particle size differences between samples, it is preferable to derive a linear function from the compressive strength of activated carbon particles around any 20 points to calculate the hardness (H) of the most frequently occurring particle size (300 μm) of the activated carbon adsorbent. D300 The hardness (H) of activated carbon particles with a particle size of 300 μm. D300 If the hardness is too low, the activated carbon particles are prone to disintegration, potentially failing to achieve the desired adsorption performance. Hardness (H) D300 If the temperature is too high, activation generally cannot proceed sufficiently, meaning that the pores required for the adsorption of toxic substances are insufficient. The hardness of activated carbon particles with a diameter of 300 μm is 2.0–30.0 N, which helps maintain the shape of the activated carbon particles and inhibits the decrease in adsorption performance. The activated carbon adsorbent of this invention, as shown in the embodiments described later, has a pore diameter peak of 0.52–0.70 nm and a pore volume of 0.45–0.55 cm³ for sub-nanopores with a pore diameter of less than 1.0 nm. 3 / g, with a pore diameter of 3–50 nm and a pore volume of 0.01–1.0 cm³. 3 When the average pore diameter is 1.7–5.0 nm, the adsorption performance of low molecular weight compounds can be maintained at a high level even when low molecular weight compounds and high molecular weight compounds coexist. Therefore, using the schematic diagrams in Figures 1 and 2, the adsorption phenomenon of activated carbon adsorbents is explained by the peak of the pore diameter, the pore volume of sub-nanopores with a pore diameter of less than 1.0 nm, the pore volume of pores with a pore diameter of 3–50 nm, and the average pore diameter. Furthermore, in the figures, symbol 10 represents activated carbon particles, 20 represents macropores, 30 represents mesopores, 40 represents micropores, 100 represents activated carbon particles of a conventional activated carbon adsorbent, X and X1 represent low-molecular-weight compounds such as urea toxins, and Y and Y1 represent high-molecular-weight compounds such as enzymes. The activated carbon adsorbent of the present invention, as specified above, is shown in Figure 1. It is assumed that multiple mesopores 30 are formed within the macropores 20 of the activated carbon particles 10, and multiple micropores 40 are further formed within each mesopore 30. That is, it has a structure with a greater number of micropores 40 corresponding to low molecular weight compounds and mesopores 30 corresponding to high molecular weight compounds. On the other hand, conventional activated carbon adsorbents have a smaller pore volume than mesopores compared to micropores. As shown in Figure 2, the mesopores 30 within the macropores 20 of activated carbon particles 100 are fewer, presumably forming a fine pore structure with multiple micropores 40 within each mesopore 30. Since the activated carbon particles 100 have a smaller pore volume than mesopores 30 compared to micropores 40, it is believed that adsorption tests on a single component will show higher adsorption performance for low molecular weight compound X. However, in an environment where low-molecular-weight compounds and high-molecular-weight compounds coexist, as shown in Figure 2, when high-molecular-weight compound Y1 is adsorbed onto the mesopore 30, the entrances of the mesopore 30, which contains multiple micropores 40, are blocked by the high-molecular-weight compound Y1. Since the mesopore 30 containing micropores 40 corresponds to the diffusion path required for the low-molecular-weight compound to diffuse when it is adsorbed onto the micropore, it is estimated that the blockage of the entrances of the mesopore 30 by the high-molecular-weight compound Y1 will hinder the path of low-molecular-weight compound X1 to the micropore 40. Furthermore, since there are fewer mesopores 30 within the macropore 20, the proportion of the diffusion path of low-molecular-weight compound X1 that is obstructed increases, and it is estimated that the adsorption performance of the low-molecular-weight compound will decrease. In contrast, the activated carbon particles 10 of the activated carbon adsorbent of the present invention have multiple mesopores 30 formed within the macropores 20. As shown in FIG1, even if a portion of the mesopores 30 are blocked by the polymer compound Y1, multiple other open mesopores 30 still exist, which is believed to ensure the path of the low-molecular-weight compound X1 to the micropores 40. Therefore, the proportion of the diffusion path of the low-molecular-weight compound X1 that is obstructed is reduced, and it is believed that the reduction in the adsorption performance of the low-molecular-weight compound can be suppressed. The activated carbon adsorbent of the present invention can be obtained by a known manufacturing method. The known manufacturing method involves: a carbonization step, in which activated carbon raw material is carbonized; and an activation step, in which the carbide obtained by the carbonization step is activated. In the carbonization step, the activated carbon raw material is contained in a sintering furnace such as a cylindrical electric furnace, and the furnace is placed in an inert environment such as nitrogen, argon, or helium. The carbonization is carried out at 300–1000°C, preferably 450–700°C, for 1–20 hours to obtain the carbide. In the activation step, the carbide obtained in the carbonization step is placed in a known heating furnace or similar environment and activated with steam at 750–1000°C, preferably 800–1000°C, and more preferably 850–950°C. The activation time can be adjusted according to the production scale and equipment, and is preferably, for example, about 0.5–50 hours. In addition to steam activation, gas activation such as carbon dioxide can also be used in the activation step. The activated carbon is then washed with dilute hydrochloric acid, and after washing with dilute hydrochloric acid, it is washed with water until the pH reaches approximately 5–7. Furthermore, the pH value is measured according to JIS K 1474 (2014). After washing with dilute hydrochloric acid, the adsorbent undergoes heating treatment in a mixture of oxygen and nitrogen, followed by water washing, as needed, to remove ash and other impurities, or residual hydrochloric acid from the heating treatment. The oxygen concentration during heating treatment is 0.1–21% by volume, the heating temperature is 150–1000℃, preferably 400–800℃, and the heating time is preferably 15 minutes to 2 hours. The activated carbon adsorbent, through various treatments to adjust the amount of surface oxides, further increases this amount through heating treatment following acid washing. The shape of the activated carbon adsorbent is not particularly limited. After activation treatment or subsequent heat treatment, it is preferable to sieve it into granular or spherical particles with an average particle size of 20–1000 μm, preferably 150–350 μm. By sieving the particle size within the above range, the surface area of ​​the activated carbon adsorbent can be appropriately ensured. Furthermore, by adjusting and classifying the particle size, the adsorption rate of the activated carbon adsorbent can be kept constant, and the adsorption capacity can be made more stable. That is, through uniform particle size, the adsorption performance in the digestive tract is stable, the hardness of the particles can be maintained, and further pulverization in the digestive tract after oral administration can be inhibited. In addition, the suitable shape of activated carbon adsorbent is spherical, but variations in the degree of sphericity caused by manufacturing are still permissible, so granular particles are also included. Phenolic resins used as raw materials for activated carbon have an aromatic ring structure in their molecules, which increases the carbonization yield. Furthermore, activation produces activated carbon with a larger surface area. Compared to activated carbon from conventional materials such as wood, coconut shells, or petroleum asphalt, the activated carbon has smaller pore sizes and higher packing density. Therefore, it is suitable for the adsorption of nitrogen-containing, low-molecular-weight (molecular weight range of tens to hundreds) ionic organic compounds, such as indophenol sulfate, aminoisobutyric acid, and tryptophan, which are pathogens of uremia or their precursors. Moreover, compared to conventional activated carbon raw materials such as wood, phenolic resins contain less ash (nitrogen, phosphorus, sodium, magnesium, etc.) and have a higher carbon content per unit mass. Therefore, activated carbon with fewer impurities can be obtained. [Example] [Preparation of activated carbon adsorbent] Using the activated carbon raw material described later, the material was placed in a cylindrical electric furnace and sealed with nitrogen gas for heating treatment. Water vapor was then injected into the furnace for activation treatment, thus obtaining the activated carbon adsorbents of Test Examples 1 to 16. [Example 1] The activated carbon raw material was a phenolic varnish-type cresol composite spherical phenolic resin produced by a well-known manufacturing method. 1 kg of this phenolic resin was placed in a cylindrical electric furnace and sealed with nitrogen. The temperature was increased to 75°C for 1 hour and maintained at 600°C for 1 hour to carbonize the spherical phenolic resin inside the furnace. Subsequently, the resulting carbonized material was heated to 900°C, and steam was injected into the furnace. The temperature was maintained at 900°C for 4 hours, and steam was added to activate it, thus obtaining the activated carbon adsorbent of Example 1. [Example 2] The activated carbon raw material used was spherical phenolic resin (manufactured by Lignyte Co., Ltd.). 10 kg of this spherical phenolic resin was placed in a cylindrical electric furnace and sealed with nitrogen. The temperature was increased at 50°C for 1 hour and maintained at 600°C for 1 hour to carbonize the spherical phenolic resin inside the furnace. Subsequently, the resulting carbonized material was heated to 900°C, and steam was injected into the furnace. The temperature was maintained at 900°C for 10 hours, and steam was added to activate it, thus obtaining the activated carbon adsorbent of Example 2. [Trial Example 3] Trial Example 3 is an activated carbon adsorbent obtained based on Trial Example 2, with the activation time set to 27 hours or less. [Trial Example 4] Trial Example 4 is an activated carbon adsorbent obtained based on Trial Example 2, with the activation time set to 33 hours or less. [Trial Example 5] Trial Example 5 is an activated carbon adsorbent obtained based on Trial Example 2, with the activation time set to 37 hours or less. [Example 6] Example 6 is a spherical adsorbent carbon (manufactured by Daewon Pharm. Co. Ltd, "Renamezin") using furan resin as the activated carbon raw material. [Prototype 7] Prototype 7 is a spherical adsorbent carbon made of phenolic resin (manufactured by Nichii Kogyo Co., Ltd., "Nichii Kogyo"). [Trial Example 8] Trial Example 8 is an activated carbon adsorbent obtained based on Trial Example 2, with the activation time set to something other than 40 hours. [Trial Example 9] Trial Example 9 is an activated carbon adsorbent obtained based on Trial Example 2, with the activation time set to 52 hours or less. [Trial Example 10] Trial Example 10 is an activated carbon adsorbent obtained based on Trial Example 2, with the activation time set to 56 hours or less. [Trial Example 11] Trial Example 11 is an activated carbon adsorbent obtained based on Trial Example 2, with the activation time set to something other than 60 hours. [Example 12] The activated carbon raw material was spherical furan resin manufactured by Asahi Organic Materials Co., Ltd. 500g of this furan resin was placed in a cylindrical electric furnace and sealed with nitrogen. The temperature was increased at 50°C for 1 hour and maintained at 500°C for 1 hour to carbonize the spherical furan resin inside the furnace. Subsequently, the resulting carbonized material was heated to 900°C, and steam was injected into the furnace. The temperature was maintained at 900°C for 5 hours, and steam was added to activate it, thus obtaining the activated carbon adsorbent of Example 12. [Example 13] The activated carbon raw material used was the same phenolic varnish-type cresol composite spherical phenolic resin as in Example 1. 6 kg of this phenolic resin was placed in a cylindrical electric furnace and sealed with nitrogen. The temperature was maintained at 150–250°C to allow it to harden sufficiently. The temperature was then increased by 50°C per hour and maintained at 600°C for 1 hour to carbonize the spherical phenolic resin in the furnace. The resulting carbonized material was then heated to 850°C, and steam was injected into the furnace. The temperature was maintained at 850°C for 36 hours, and steam was added to activate the carbon, thus obtaining the activated carbon adsorbent of Example 13. [Trial Example 14] Trial Example 14 is an activated carbon adsorbent obtained in accordance with Trial Example 1, except that the activated carbon raw material used is the same as that of Trial Example 1, and the heating rate is set to 50°C / 1 hour and the activation time is set to 6 hours. [Example 15] The activated carbon raw material was spherical cellulose resin that had undergone flame retardant treatment, manufactured using a well-known method. 400g of this flame-retardant cellulose resin was placed in a cylindrical electric retort furnace and sealed with nitrogen. The temperature was increased at 50°C for 1 hour and maintained at 250°C for 1 hour. Subsequently, the resulting carbonized material was heated to 900°C, and steam was injected into the furnace. The temperature was maintained at 900°C for 3 hours, and steam was added to activate it, thus obtaining the activated carbon adsorbent of Example 15. [Example 16] Example 16 is an activated carbon adsorbent obtained in accordance with Example 1, except that the activated carbon raw material used is the same as that of Example 1, which is phenolic varnish type cresol composite spherical phenolic resin, and the heating rate is set to 50°C / 1 hour and the activation time is set to 8 hours. [Determination of Activated Carbon] For the activated carbon adsorbents in Examples 1-16, the following parameters were determined: pore volume of sub-nanopores, pore volume of ultramicropores, pore diameter peak, total micropore volume, pore volume of pores with diameters of 3-50 nm, monolayer adsorption capacity, total specific surface area, total pore volume, average pore diameter, average diameter of activated carbon particles, average hardness of activated carbon particles, hardness of particles with a diameter of 300 μm, and volume ratio. The determination results for each example are shown in Tables 1-3 below. [Pore Volume of Sub-nanopores] For the activated carbon adsorbents of Examples 1-16, the pore volume (cm³) of sub-nanopores (pore diameter less than 1 nm) was measured. 3 / g). The pore volume of the sub-nanopores was determined using a surface area / pore distribution measuring device (MicrotracBEL Co., Ltd. "BELSORP-miniII"), measuring the carbon dioxide adsorption isotherm at 298K. The obtained carbon dioxide adsorption isotherm was analyzed by GCMC method with the activated carbon adsorbent set to graphite carbon and the pore shape set to a slit model. [Pore Volume of Ultramicropores] For the activated carbon adsorbents in Examples 1-16, the carbon dioxide adsorption isotherms obtained in the above measurements were similarly analyzed by GCMC, and the pore volume (cm³) of pores with a diameter less than 0.7 nm (ultramicropores) was calculated. 3 / g). [Peak of pore diameter] For the activated carbon adsorbents of Examples 1 to 16, the carbon dioxide adsorption isotherms obtained in the above measurements were analyzed by GCMC method to determine the peak of pore diameter based on the pore volume of each pore diameter. [Pore Volume of All-Micropores] For the activated carbon adsorbents in Examples 1-16, an automated specific surface area / pore distribution measuring device (MicrotracBEL Co., Ltd. "BELSORP-miniII") was used to measure the nitrogen adsorption isotherm at 77 K, and the pore distribution was analyzed by the MP method (Micropore method) to determine the pore volume (cm³) of 0.42-2 nm (all-micropores). 3 / g). [Pore volume with a diameter of 3–50 nm] For the activated carbon adsorbents in Examples 1–16, the pore volume (cm³) of 3–50 nm was determined by analyzing the pore distribution using the DH method on the nitrogen adsorption isotherms obtained in the above measurements. 3 / g). [Monolayer Adsorption Capacity] For the activated carbon adsorbents in Examples 1-16, the monolayer adsorption capacity (cm³) was determined by the BET method based on the nitrogen adsorption isotherms obtained in the above measurements. 3 / g). [Total Specific Surface Area] For the activated carbon adsorbents of Examples 1-16, the total specific surface area (m²) was determined by the BET method based on the nitrogen adsorption isotherms obtained in the above measurements. 2 / g)(BET specific surface area. [Total Pore Volume] For the activated carbon adsorbents of Examples 1-16, the total pore volume (cm³) was determined by the BET method based on the nitrogen adsorption isotherms obtained in the above measurements. 3 / g). [Average pore diameter] For the activated carbon adsorbents of Examples 1-16, the total specific surface area (m²) obtained in the above measurements was used. 2 The average pore diameter (nm) is calculated from the values ​​of (g) and total pore volume (mL / g) using the aforementioned formula (ii). [Average Diameter of Activated Carbon Particles] For the activated carbon adsorbents of Test Examples 1 to 16, 20 random points were taken from activated carbon particles with a diameter of 150 to 500 μm, and the particle diameter was measured using a digital micrometer (manufactured by Shinwa Measurement Co., Ltd.). The average value was taken as the average diameter (μm). [Average Hardness of Activated Carbon Particles] For the activated carbon adsorbents of Test Examples 1 to 16, the maximum compressive strength of activated carbon particles with diameters measured by the aforementioned digital micrometer was determined using a digital tensile tester (IMADA Co., Ltd. "ZTA-50N") before the activated carbon particles were destroyed, and the average value of the test particles was taken as the average hardness (N). [Hardness of 300μm Particle Size] For the activated carbon adsorbents in Examples 1-16, the particle diameter and compressive strength data of 20 activated carbon particles measured by the aforementioned method were plotted, and a linear function was derived using a calculation software. After confirming that the correlation coefficient of the graph excluding deviation values ​​was 0.7 or higher, the hardness of 300μm particle size was calculated using the linear function formula. [Volume Ratio] For the activated carbon adsorbents of Examples 1-16, the pore volume (cm³) of the sub-nanopores obtained in the above determination was used. 3 / g) and the micropore volume (cm³) of mesopores with a micropore diameter in the range of 3–50 nm. 3 The value of / g) is used to calculate the volume ratio using the aforementioned formula (i). [Adsorption performance test] For the activated carbon adsorbents of test examples 1 to 16, as an adsorption performance test of low molecular weight compounds in the coexistence of low molecular weight compounds and high molecular weight compounds, a toxin adsorption test and a coexistence adsorption test (1) and a coexistence adsorption test (2) were conducted. [Toxin Adsorption Test] In the toxin adsorption test, three nitrogen-containing low-molecular-weight compounds, namely tryptophan, indole, and indoleacetic acid, which are toxic substances that may cause uremia, were selected. Each substance was dissolved separately in a phosphate buffer solution at pH 7.4 to prepare a mixed solution of the three toxins at a concentration of 0.1 g / L. 0.1 g of activated carbon adsorbent (Examples 1-16), which had been pre-dried at 120°C for at least 15 minutes in a static desiccator, was added to each of the three toxin mixed solutions, and the mixture was shaken at 37°C for 3 hours. Subsequently, the filtrate obtained by filtration using a membrane filter was analyzed using high-performance liquid chromatography (HPLC) (Agilent Technologies Inc. "1260 Infinity II LC system") with gradient extraction. The adsorption rate (%) was determined by the difference in peak area before and after adsorption for each adsorbed substance (tryptophan, indole, and indoleacetic acid). In the gradient extraction, mobile phase A used an aqueous solution containing 0.05% trifluoroacetic acid, and mobile phase B used an ethanolic solution containing 0.05% trifluoroacetic acid. The separation column used was an "XBridge (registered trademark) Premier Protein BEH C4 300Å 2.5μm Column" (manufactured by Waters Corporation, Japan). The column heating temperature was set to 60°C, and the target substance was detected using a UV wavelength of 278nm. Detailed gradient extraction conditions are shown in Table 4. [Coexistence Adsorption Test (1)] In the coexistence adsorption test (1), three toxic substances were selected: tryptophan, indole, and indoleacetic acid. One enzyme (high molecular weight compound) was selected: α-amylase. The three toxic substances were dissolved at 0.1 g / L and α-amylase at 1 g / L in a phosphate buffer solution at pH 7.4 to prepare a mixed solution of the three toxins and enzymes. The adsorption rate (%) of each adsorbed substance (tryptophan, indole, indoleacetic acid, and α-amylase) was determined using the same procedure as in the toxin adsorption test. Furthermore, because the molecular weight of α-amylase is higher than that of the toxic substances, the measured peak intensity was lower, so the concentration was set at 10 times higher. [Coexistence Adsorption Test (2)] In the coexistence adsorption test (2), the toxic substances selected were "tryptophan", "indole", and "indoleacetic acid", and the enzymes selected were "α-amylase", "pepsin", "trypsin", and "lipase". Each substance was dissolved in a phosphate buffer solution at pH 7.4 to prepare a mixed solution of the three toxins and four enzymes with a concentration of 0.1 g / L. The adsorption rate (%) of each adsorbed substance (tryptophan, indole, and indoleacetic acid) was calculated using the same procedure as in the toxin adsorption test. In addition, in the coexistence adsorption test (2), due to the technical difficulties in separating the enzymes, the adsorption rate was only calculated for the toxic substances. [Calculation of Adsorption Reduction Rate] For each of the toxin adsorption test, coexistence adsorption test (1), and coexistence adsorption test (2), the average adsorption rate of the toxins in each adsorption test ([adsorption rate of 3 toxins] ÷ 3) is calculated from the adsorption rates of the three toxins (tryptophan, indole, and indoleacetic acid). Using the average adsorption rate of the toxins in the toxin adsorption test as the standard adsorption rate, and the average adsorption rate of the toxins in the coexistence adsorption test (1) or coexistence adsorption test (2) as the coexistence adsorption rate of each coexistence adsorption test, the adsorption reduction rate (%) is calculated using the following formula (iii). Furthermore, the adsorption reduction rate is an indicator of the degree to which the adsorption rate of low molecular weight compounds decreases in the presence of high molecular weight compounds compared to an environment where high molecular weight compounds do not coexist. [Evaluation of Adsorption Performance] The molecular weights of tryptophan, indoleacetic acid, and indole decrease in the order of 204, 175, and 117, respectively. Indole, in particular, is highly hydrophobic and readily adsorbs onto activated carbon, making it less susceptible to the influence of coexisting substances on the adsorption rate. Therefore, in each adsorption test, for the adsorption rates of tryptophan, indoleacetic acid, and the average adsorption rate of toxins, a result of 50% or higher was rated as "Good (○)," and a result below 50% was rated as "Poor (×)." For indole, an adsorption rate of 95% or higher was rated as "Good (○)," and a result below 95% was rated as "Poor (×)." Furthermore, for α-amylase, an adsorption rate below 30% and an adsorption reduction rate above 30% were rated as "Good (○)," and a result above 30% was rated as "Poor (×)." The results and evaluations are shown in Tables 5-7. [Results and Investigations] For the activated carbon adsorbents in Examples 1-16, adsorption tests were conducted on toxins (low molecular weight compounds) and enzymes (high molecular weight compounds) without coexistence, coexistence adsorption tests (1) with multiple toxic substances and one enzyme, and coexistence adsorption tests (2) with multiple toxic substances and multiple enzymes. The results shown in Tables 5-7 were used to investigate the changes in adsorption performance under the coexistence of low molecular weight compounds and high molecular weight compounds. In the toxin adsorption test, the adsorption performance for various toxic substances was measured in an environment where no polymeric compounds were present. In Test Example 1, although the average adsorption rate of the toxin was higher than the benchmark value, the adsorption performance for tryptophan and indoleacetic acid was insufficient. Furthermore, Test Example 2 did not exhibit sufficient toxin adsorption performance. On the other hand, Test Examples 3 through 16 all showed good toxin adsorption performance. In the coexistence adsorption test (1), the adsorption performance of multiple toxic substances was measured in an environment where multiple toxic substances coexist with one type of enzyme. In Test Examples 1 to 7, although the adsorption rate of some indoles was higher than the benchmark value, the overall trend was that the adsorption rate of each toxic substance was lower than the benchmark value, indicating that sufficient toxin adsorption performance could not be obtained in the coexistence of one polymer compound. Furthermore, focusing on the adsorption reduction rate, an indicator of the decrease in adsorption rate of low-molecular-weight compounds in the presence of high-molecular-weight compounds, Examples 1 and 2, which showed lower adsorption rates in the toxin adsorption test, exhibited lower adsorption reduction rates, while Examples 3 to 7, which showed good adsorption rates in the toxin adsorption test, showed higher adsorption reduction rates. This indicates that, in Examples 3 to 7, although the toxin adsorption performance was good, it was significantly reduced in the presence of one high-molecular-weight compound. In addition, Examples 1 and 2 showed that while the lower toxin adsorption performance could suppress the adsorption reduction rate, the toxin adsorption performance in the presence of a single high-molecular-weight compound was insufficient. On the other hand, in Test Examples 8-16, the average adsorption rates of each toxic substance and toxin were good in the presence of a single polymer compound, and the adsorption reduction rate was also low and good. Thus, Test Examples 8-16 show that the toxin adsorption performance is good, and the toxin adsorption performance can be maintained at a high level even in the presence of a single polymer compound. In the coexistence adsorption test (2), the adsorption performance of various toxic substances was measured under conditions where multiple toxic substances and multiple enzymes coexisted. Examples 1-7 and 8-16 showed almost the same tendency as in the coexistence adsorption test (1). Thus, it was shown that in Examples 1-7, the toxin adsorption performance decreased under the coexistence of multiple polymers, while in Examples 8-16, the toxin adsorption performance was maintained at a high level even under the coexistence of multiple polymers. Thus, it can be seen that regardless of whether one or more polymeric compounds coexist, Test Examples 8-16 maintained a high level of toxin adsorption performance in the presence of these polymeric compounds, while Test Examples 1-7 showed reduced toxin adsorption performance. Therefore, the differences in physical properties between Test Examples 8-16 and Test Examples 1-7 are discussed in Tables 1-3. Firstly, regarding the adsorption performance of toxic substances, the pore volume of sub-nanopores (pore diameter less than 1 nm) and ultramicropores (pore diameter less than 0.7 nm) corresponding to the adsorption of toxic substances (low molecular weight compounds) were compared between Test Examples 1 and 2 and Test Examples 3-16. Regarding the pore volume of sub-nanopores, Test Examples 3-16, which showed good adsorption performance, had larger values ​​than Test Examples 1 and 2, where the adsorption performance of each toxic substance in the toxin adsorption test was insufficient. On the other hand, a different trend was observed in the pore volume of ultramicropores. Therefore, the pore volume of sub-nanopores is considered an effective indicator of the adsorption performance of toxic substances. Based on the measurement results of Test Examples 3-16, the suitable conditions were determined to be 0.45–0.55 cm⁻¹. 3 Approximately / g. Secondly, regarding the adsorption performance of toxic substances under coexisting conditions, Test Examples 3-7 and Test Examples 8-16 were compared based on the peak of the micropore diameter, the total micropore volume, the micropore volume with a diameter of 3-50 nm, the monolayer adsorption capacity, the total specific surface area, the total micropore volume, the average micropore diameter, the average diameter of the activated carbon particles, the average hardness of the activated carbon particles, the hardness of particles with a diameter of 300 μm, and the volume ratio. Thus, no different trends were observed between Test Examples 3-7 and Test Examples 8-16 in terms of the total micropore volume, the monolayer adsorption capacity, the total specific surface area, the total micropore volume, the average diameter of the activated carbon particles, the average hardness of the activated carbon particles, and the hardness of particles with a diameter of 300 μm. On the other hand, different trends can be observed between Test Examples 3-7 and Test Examples 8-16 regarding the peak of the pore diameter, the pore volume of pores with diameters of 3-50 nm, the average pore diameter, and the volume ratio. The peak of the pore diameter is based on CO... 2. The GCMC method for adsorption uses micropores as the measurement range, and the peak value corresponds to the diameter of the pores within the micropores. Therefore, when comparing Test Examples 3-7 with Test Examples 8-16, the peak value of the pore diameter in Test Examples 8-16 is larger than that in Test Examples 3-7. The pore volume with a pore diameter of 3–50 nm refers to the range of pore diameters of 3–50 nm corresponding to the adsorption of enzymes (polymers) within the mesopores measured by the DH method, and can be used as an indicator of the adsorption performance of enzymes. Therefore, when comparing Test Examples 3–7 with Test Examples 8–16, the pore volumes with pore diameters of 3–50 nm in Test Examples 8–16 are all greater than those in Test Examples 3–7. The average pore diameter can be used as one of the indicators of the adsorption performance of activated carbon adsorbents. Therefore, when comparing Test Examples 3-7 with Test Examples 8-16, the average pore diameter of Test Examples 8-16 is approximately greater than that of Test Examples 3-7. Therefore, for activated carbon adsorbents, in addition to the pore volume of sub-nanopores, which serves as an indicator of toxin adsorption performance, the physical properties defined by the peak of the pore diameter, the pore volume of pores with a diameter of 3-50 nm, and the average pore diameter can also be effectively used as indicators of the ability to maintain a high level of adsorption performance for low-molecular-weight compounds (toxic substances) even when low-molecular-weight compounds and high-molecular-weight compounds coexist. Therefore, based on the relationship between test examples 3-7 and test examples 8-16, and considering the peak value of the pore diameter, the pore volume of pores with diameters of 3-50 nm, and the average pore diameter, if suitable conditions are derived from the measurement results, it is determined that the peak value of the pore diameter is approximately 0.52-0.70 nm, and the pore volume of pores with diameters of 3-50 nm is 0.01-1.00 cm³. 3 The average pore size is approximately 1.7–5.0 nm. Therefore, activated carbon adsorbents suitable for toxin adsorption in the coexistence of toxic substances (low-molecular-weight compounds) and enzymes (high-molecular-weight compounds) are estimated to have a micropore volume of 0.45–0.55 cm³. 3 It possesses excellent toxin adsorption performance at around / g, and must meet all of the following physical properties: pore diameter peak of approximately 0.52–0.70 nm, pore diameter of 3–50 nm, and pore volume of 0.01–1.00 cm³. 3 The average pore size is approximately 1.7–5.0 nm. Furthermore, comparing Test Examples 8-16, which are suitable for adsorbing toxins under coexistence conditions, Test Example 16 shows a higher adsorption rate of α-amylase in the coexistence adsorption test (1) compared to the other Test Examples 8-15. Considering further improving the quality of the activated carbon adsorbent, a lower adsorption rate of enzymes such as α-amylase under coexistence conditions is preferable as it is less likely to cause side effects such as indigestion or loss of appetite. Therefore, comparing the physical properties of Test Example 16 with those of Test Examples 8-15, the volume ratio of Test Example 16 is smaller compared to the other Test Examples 8-15. The volume ratio, an indicator of the adsorption performance of toxic substances (the volume of sub-nanopores) to the volume of pores with a diameter of 3-50 nm (the volume of enzymes), represents the balance between sub-nanopores and pores with a diameter of 3-50 nm in the activated carbon adsorbent. In Example 16, the volume ratio was 0.54, indicating an excess of pores with a diameter of 3-50 nm compared to the volume of sub-nanopores. Therefore, in Example 16, it was determined that α-amylase was over-adsorbed. Based on the measurement results of Examples 8-15, the suitable condition for avoiding over-adsorption of enzymes (high molecular weight compounds) such as α-amylase is a volume ratio of approximately 3-50. Furthermore, activated carbon adsorbents, if assuming they are formulated into tablets for oral administration, preferably possess a certain degree of hardness. A suitable hardness for activated carbon adsorbents is approximately 2.0 to 30.0 N for activated carbon particles with a particle size of 300 μm. Therefore, it can be seen that among the activated carbon adsorbents in Examples 1-16, the activated carbon adsorbents in Examples 8-13 exhibit good performance in all aspects, including toxin adsorption under coexisting conditions, prevention of excessive enzyme adsorption, and hardness. [Industrial Applicability] The activated carbon adsorbent of this invention maintains high adsorption performance for low-molecular-weight compounds even when both low-molecular-weight and high-molecular-weight compounds coexist. Furthermore, it exhibits excellent toxin adsorption performance in vivo, even when toxic substances from low-molecular-weight compounds and enzymes from high-molecular-weight compounds coexist. Therefore, it is expected to serve as a substitute for conventional activated carbon adsorbents. 10: Activated carbon particles; 20: Macropores; 30: Mesopores; 40: Micropores; 100: Activated carbon particles of conventional activated carbon adsorbents; X, X1: Low molecular weight compounds; Y, Y1: High molecular weight compounds. [Figure 1] is a schematic diagram of the adsorption phenomenon of an activated carbon adsorbent according to an embodiment of the present invention. [Figure 2] is a schematic diagram of the adsorption phenomenon of a conventional activated carbon adsorbent. 10: Activated carbon particles 20: Giant Hole 30: Mesoporous 40: Micropores X, X1: Low molecular weight compounds Y,Y1: Polymer compounds

Claims

1. An activated carbon adsorbent, characterized in that: the peak value (Wp) of the pore diameter, based on the pore volume calculated by the GCMC method for CO2 adsorption, is 0.52–0.70 nm; the pore volume (VSN) of sub-nanopores with a pore diameter of less than 1.0 nm, calculated by the aforementioned GCMC method, is 0.45–0.55 cm³ / g; the pore volume (VME) of the pore diameter of 3–50 nm, calculated by the DH method for N2 adsorption, is 0.01–1.00 cm³ / g; and the average pore diameter measured by the BET method is 1.7–5.0 nm; wherein the raw material of the aforementioned activated carbon adsorbent is a resin carbide of phenolic resin or cellulose.

2. The activated carbon adsorbent of claim 1, wherein the volume ratio (VSN / ME) of the aforementioned sub-nanopores as specified in formula (i) to the aforementioned pore volume (VME) with a pore diameter of 3 to 50 nm is 3 to 50; 3. The activated carbon adsorbent as claimed in item 1 or 2, wherein the hardness (HD300) of the activated carbon particles with a particle size of 300 μm, calculated from the average hardness of the activated carbon particles with a diameter of 150 to 500 μm, is 2.0 to 30.0 N.

4. The activated carbon adsorbent as claimed in item 1 or 2, wherein the aforementioned activated carbon adsorbent is a therapeutic or preventative agent for oral administration of nephropathy or hepatopathy.

5. The activated carbon adsorbent as claimed in claim 3, wherein the aforementioned activated carbon adsorbent is a therapeutic or preventative agent for oral administration of nephropathy or hepatopathy.

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