Adsorbent

Abstract

To provide an adsorbent capable of efficiently adsorbing phosphorus in water as well as nitrogen.SOLUTION: A method for producing an adsorbent includes forming a coating layer that covers at least a part of a core containing porous carbide through stepwise addition of a mist-like solvent under the presence of carbon dioxide while mixing the core with an additive. The additive may include a magnesium compound. The magnesium compound may be magnesium hydroxide. The coating layer may contain Mg in an amount of 1 mass% or more and 30 mass% or less with respect to the total mass of the core and the coating layer.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] One embodiment of the present invention relates to a method for producing an adsorbent. [Background technology]

[0002] It is known that an adsorbent containing iron and porous carbide having carbon prepared from biomass as a basic material can adsorb phosphate ions derived from phosphoric acid, and can therefore be used to improve the water quality in water bodies such as rivers, lakes, and oceans. In addition, by coating the surface of this adsorbent with an inorganic compound such as gypsum (calcium sulfate), it is possible to prevent the adsorbent from disintegrating in water (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-138550 [Patent Document 2] JP 2022-138628 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one embodiment of the present invention is to provide an efficient method for producing an adsorbent. [Means for solving the problem]

[0005] One embodiment of the invention is a method for making an adsorbent, comprising mixing a porous charred core with an additive in the presence of carbon dioxide while incrementally adding atomized solvent to form a coating layer over at least a portion of the core. [Brief description of the drawings]

[0006] [Figure 1A]FIG. 1 is a schematic perspective view of an adsorbent according to one embodiment of the present invention. [Figure 1B] FIG. 1 is a schematic end view of an adsorbent according to one embodiment of the present invention. [Figure 1C] FIG. 4 is a schematic end view of an adsorbent according to a modified example of the present invention. [Diagram 2] 1 is a flowchart showing a method for producing an adsorbent according to one embodiment of the present invention. [Figure 3A] FIG. 2 is a schematic side view illustrating a coating device used in a method for producing an adsorbent according to one embodiment of the present invention. [Figure 3B] FIG. 2 is a schematic top view illustrating a coating device used in a method for producing an adsorbent according to one embodiment of the present invention. [Figure 4] FIG. 1 is a conceptual diagram showing a carbon dioxide storage system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, each embodiment of the present invention will be described with reference to the drawings, etc. However, the present invention can be embodied in various forms without departing from the gist of the present invention, and should not be construed as being limited to the description of the embodiments exemplified below.

[0008] In order to make the explanation clearer, the drawings may show the width, thickness, shape, etc. of each part diagrammatically compared to the actual embodiment, but these are merely examples and are not intended to limit the interpretation of the present invention.

[0009] In this specification and claims, the expression "a structure is exposed from another structure" means an embodiment in which a part of a structure is not covered by another structure, and includes an embodiment in which the part not covered by the other structure is covered by yet another structure.

[0010] Hereinafter, an adsorbent according to one embodiment of the present invention and a method for producing the same, a water purification method using the adsorbent, and a carbon dioxide storage system using the adsorbent will be described.

[0011] 1. Structure of the adsorbent (1) Overall structure FIG. 1A shows a schematic perspective view of the adsorbent 100, and FIG. 1B shows a schematic view of an end surface perpendicular to the length direction. As shown in these figures, the adsorbent 100 basically comprises a core 102 and a coating layer 104 covering the core 102. The coating layer 104 may cover the entire surface of the core 102, or, although not shown, may cover only a part of the surface of the core 102. In the latter case, other parts of the surface of the core 102 are exposed from the coating layer 104. By covering the surface of the core 102 with the coating layer 104, physical strength is imparted to the adsorbent 100. Therefore, even if the adsorbent 100 is placed in water for a long period of time to improve the water quality of water bodies such as rivers, lakes, and seas, the adsorbent 100 is prevented from being eroded by water and collapsing, and can function as an adsorbent for a long period of time.

[0012] A schematic diagram of an end surface perpendicular to the length direction of a modified adsorbent 100a is shown in FIG. 1C. As shown in FIG. 1C, the adsorbent 100a may have an intermediate layer 106 between the core 102 and the coating layer 104 as an optional configuration. Like the coating layer 104, the intermediate layer 106 may cover the entire surface of the core 102, or may cover only a portion of the surface of the core 102. A portion of the core 102 may be exposed from both the coating layer 104 and the intermediate layer 106, or may be in direct contact with the coating layer 104. A portion of the intermediate layer 106 may also be exposed from the coating layer 104.

[0013] The shape of the adsorbent 100 is arbitrary, and may be a plate shape, or may be a pellet shape as shown in FIG. 1A. In the case of a pellet shape, the shape of the adsorbent 100 may be a sphere or a cylinder, or may be a cylinder (prism) with polygonal end faces, such as an elliptical cylinder, triangular prism, quadrangular prism, pentagonal prism, or hexagonal prism (not shown). The adsorbent 100 may also have the shape of a sphere, cylinder, elliptical cylinder, or prism with a missing part. Therefore, the adsorbent 100 does not need to have the shape of a perfect sphere, cylinder, or prism, and may occupy, for example, 75% or more of the volume of the adsorbent 100 relative to the total volume of a cylinder with the smallest volume in which the adsorbent 100 is inscribed.

[0014] When the adsorbent 100 is a cylinder or can be regarded as a cylinder, its diameter D may be 1 mm or more and 20 mm or less, 2 mm or more and 11 mm or less, or 3 mm or more and 8 mm or less. 2 More than 300mm 2 The aspect ratio of the adsorbent 100, i.e., the ratio of the length L to the diameter D (L / D), is also arbitrary and can be, for example, 0.5 to 5.0. Specifically, the length L can be 0.5 mm to 100 mm, 1 mm to 20 mm, 3 mm to 15 mm, or 6 mm to 12 mm.

[0015] (2) Core The core 102 mainly determines the shape of the adsorbent 100, and has a porous carbide as a basic skeleton. Therefore, the core 102 contains carbon as a main component.

[0016] Porous charcoal is a charcoal produced by using organic matter as a raw material and heating and carbonizing the organic matter under conditions of low oxygen concentration. An example of organic matter is biomass. Here, biomass refers to substances derived from living organisms and their metabolites. Specifically, wooden molded products such as plank-shaped or column-shaped wood, thinning wood, pruning waste, construction waste wood, powdered sawdust, and particle boats can be mentioned. There is no restriction on the type of wood, and cedar, cypress, and bamboo can be used. Other examples of biomass include agricultural waste such as rice husks, bagasse, corn cobs and leaves, and agricultural by-products such as straw, wheat straw, and hay. Other examples include plants that are the raw material for fibers such as hemp, flax, cotton, sisal, abaca, and palm hair. Other examples include algae such as seaweed. Other examples include food waste and silage obtained from animal manure. As will be described later, by using biomass as the raw material for porous charcoal, a system for storing carbon dioxide in the atmosphere can be constructed.

[0017] The core 102 may further include a first binder as an optional component. The first binder functions as an auxiliary component for forming the core 102 in the granulation process described later. As the first binder, an organic binder and / or an inorganic binder can be used. As the organic binder, for example, one or more selected from molasses, blackstrap molasses, starch, dextrin, corn starch, rice bran, polyvinyl alcohol, a copolymer of vinyl acetate and ethylene or a saponified product thereof, pulp waste liquor, lignin sulfonate, carboxymethyl cellulose, hydroxypropyl methyl cellulose, sodium alginate, phenolic resin, and tar pitch can be mentioned. As the inorganic binder, for example, cement, granulated blast furnace slag, fly ash, gypsum (calcium sulfate), calcined gypsum obtained by heating and dehydrating gypsum, sodium silicate, etc. can be mentioned. In particular, inorganic binders are easy to handle and have low solubility in water, so that they are less likely to run off into water areas, and therefore have a small impact on the environment. Furthermore, inorganic binders are preferable because they have high weather resistance and can provide the core 102 with sufficient strength.

[0018] Core 102 may further include an alkaline earth metal as an optional component. The alkaline earth metal is included in core 102 as an alkaline earth metal compound, more specifically, as a magnesium compound or a calcium compound. Examples of magnesium compounds include magnesium hydroxide, magnesium sulfate, magnesium carbonate, magnesium bicarbonate, magnesium oxide, etc., and examples of calcium compounds include calcium hydroxide, calcium sulfate, calcium carbonate, calcium bicarbonate, calcium oxide, etc.

[0019] The core 102 may further include iron as an optional component. The iron is added to the core 102 as iron powder. Therefore, the core 102 may include iron oxide or iron hydroxide generated by surface oxidation, in addition to zero-valent iron. The iron in the iron oxide and iron hydroxide may be divalent or trivalent. Also, the iron may exist in a mixed valence state. Therefore, examples of the iron oxide include wustite (FeO), hematite or maghemite (Fe2O3), and magnetite (Fe3O4). In addition to oxygen, the iron powder may contain sulfur, phosphorus, manganese, silicon, vanadium, copper, titanium, and the like as impurities. In other words, the core 102 may contain sulfur, phosphorus, manganese, silicon, vanadium, copper, or titanium. The purity of the iron in the iron powder may be selected from the range of 90.0% to 99.9% or 95.0% to 99.0%.

[0020] There is no restriction on the size of the iron powder, i.e., the average particle size, and the average particle size is, for example, 20 μm to 500 μm or 50 μm to 200 μm. Here, the average particle size of the iron powder is a value obtained by analyzing an image obtained by observing the iron powder under a microscope, determining the particle sizes of a plurality of iron particles, and averaging them. For example, the diameter of a circle inscribing the projection surface of each iron particle in the microscope image or the length of one side of a square can be used as the particle size of each iron particle. There is also no restriction on the shape of the iron powder, and for example, iron powder having an average circularity of 50 to 100, 70 to 95, or 80 to 90 may be included in the core 102. Here, the average circularity is one of the parameters that represent the shape of each iron particle included in the iron powder, and is a value obtained by analyzing an image obtained by observing the iron powder under a microscope, determining the circularity of a plurality of iron particles, and averaging them. For example, the circularity can be a value obtained by dividing the perimeter of a circle having an area equal to the area of ​​the projection surface of each iron particle in the microscope image by the perimeter of the projection surface of each iron particle in the microscope image. Alternatively, the circularity may be determined by dividing the area of ​​the projection surface by the area of ​​a circle inscribed in the projection surface.

[0021] (3) Coating layer The coating layer 104 includes a magnesium compound. The coating layer 104 may further include a binder (hereinafter, a second binder) and / or iron. There is no restriction on the thickness of the coating layer 104, and it may be, for example, 10 μm to 5 mm, 20 μm to 3 mm, 50 μm to 500 μm, or 100 μm to 300 μm. Preferably, the coating layer 104 that contributes to the adsorption of phosphorus and nitrogen in water is thicker than the intermediate layer 106.

[0022] Examples of magnesium compounds include magnesium hydroxide, magnesium sulfate, magnesium carbonate, magnesium hydrogen carbonate, magnesium oxide, and the like, and one or more selected from these are contained in the coating layer 104. Among these magnesium compounds, magnesium hydroxide, magnesium oxide, or magnesium carbonate is preferred because they are inexpensive, allow easy formation of the coating layer 104, and have high adhesion to the core 102.

[0023] The second binder may contain materials that can be used in the first binder. The second binder and the first binder may contain the same materials or different materials.

[0024] The iron of any composition may include materials available as iron powder in the core 102. The iron powder in the core 102 and the coating layer 104 may include materials that are the same in composition, particle size, and shape, or may include materials that are different.

[0025] (4) Middle class The intermediate layer 106 may be a layer containing magnesium carbonate. There are no restrictions on the thickness of the intermediate layer 106, and it may be appropriately selected from the range of, for example, 1 μm to 500 μm, 10 μm to 300 μm, or 20 μm to 100 μm. The intermediate layer 106 may contain other magnesium compounds such as magnesium hydroxide, magnesium oxide, magnesium hydrogen carbonate, and magnesium sulfate in addition to magnesium carbonate.

[0026] By covering the entirety or part of the core 102 with the intermediate layer 106, the coating layer 104 can be formed uniformly on the intermediate layer 106, and peeling off in water can be prevented.

[0027] (5) Composition All materials are mixed together to make a total of 100% by mass. The porous carbide, which is the basic skeleton of the core 102, is contained in the adsorbent 100 in a composition of 20% by mass to 99% by mass, 50% by mass to 90% by mass, or 60% by mass to 90% by mass with respect to the dry mass of the adsorbent 100 (i.e., the total mass of the core 102 and the coating layer 104 excluding water). By adopting the above composition, a core 102 that is lightweight and has sufficient strength can be formed. The composition of the porous carbide is controlled by adjusting the charge ratio during the production of the adsorbent 100. The composition of the porous carbide in the adsorbent 100 may also be determined from a quantitative value of carbon obtained by using, for example, a combustion / infrared absorption method.

[0028] When the core 102 contains the first binder, the first binder is contained in the adsorbent 100 in a composition of 1% by mass to 50% by mass, 10% by mass to 40% by mass, or 10% by mass to 30% by mass, based on the total mass of the adsorbent 100. By adopting the above composition, the core 102 can be easily molded. The composition of the first binder is controlled by adjusting the charge ratio during the manufacture of the adsorbent 100. The composition of the first binder may also be determined from a measured value. For example, when the first binder contains calcium sulfate, the composition may be determined from a quantitative value of sulfur obtained using ICP atomic emission spectrometry (ICP-AES) or combustion / infrared absorption method, or a quantitative value of calcium obtained using atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), potassium permanganate volumetric method, or the like.

[0029] When the core 102 contains an alkaline earth metal, the alkaline earth metal is contained in a composition of 1 mass % to 50 mass %, 5 mass % to 30 mass %, or 10 mass % to 20 mass % relative to the total mass of the adsorbent 100. The composition of the alkaline earth metal is controlled by adjusting the charge ratio during the production of the adsorbent 100. The composition of the alkaline earth metal may also be quantified by, for example, ICP-OES or inductively coupled plasma mass spectrometry (ICP-MS).

[0030] When core 102 contains iron, the iron content is from 1 mass % to 20 mass %, from 1 mass % to 10 mass %, or from 5 mass % to 10 mass % relative to the total mass of adsorbent 100. The iron composition is controlled by adjusting the charge ratio during production of adsorbent 100. The iron composition may also be quantified by, for example, ICP-OES or ICP-MS.

[0031] The magnesium compound contained in the coating layer 104 is contained in a composition of 1% by mass to 30% by mass, or 5% by mass to 30% by mass, relative to the total mass of the adsorbent 100. Alternatively, the composition of the magnesium compound may be adjusted so that the magnesium contained in the coating layer 104 is 1% by mass to 30% by mass, 5% by mass to 25% by mass, or 10% by mass to 20% by mass, relative to the total mass of the adsorbent 100. Since the mass of the coating layer 104 is extremely small compared to the mass of the core 102, the coating layer 104 contains an extremely high concentration of magnesium. Specifically, the coating layer 104 may contain 1% by mass to 30% by mass of magnesium relative to the dry mass of the coating layer 104. The magnesium compound or the composition of magnesium is controlled by adjusting the charge ratio during the production of the adsorbent 100. In addition, for example, the magnesium may be quantified by applying ICP-OES or inductively coupled plasma mass spectrometry (ICP-MS), and the composition of magnesium and the magnesium compound may be determined from the obtained measured value.

[0032] The second binder is contained in a composition of 0.1% by mass to 10% by mass, 1% by mass to 5% by mass, or 1% by mass to 3% by mass, relative to the total mass of the adsorbent 100. The composition of the second binder is also controlled by adjusting the charge ratio during the manufacture of the adsorbent 100. As with the first binder, the composition of the second binder may be determined from a measured value. When the magnesium compound and the second binder contained in the coating layer 104 satisfy the above composition, it is possible to prevent the adsorbent 100 from collapsing in water and to achieve high adsorption capacity for phosphorus and nitrogen.

[0033] When coating layer 104 contains iron, the iron content is, for example, 1% by mass to 15% by mass, 1% by mass to 10% by mass, or 5% by mass to 10% by mass, relative to the total mass of adsorbent 100. The iron composition is controlled by adjusting the charge ratio during production of adsorbent 100. The iron composition may also be quantified, for example, by ICP-OES or ICP-MS.

[0034] When the adsorbent 100a includes the intermediate layer 106, the composition of magnesium carbonate included in the intermediate layer 106 may be, for example, 0.1% by mass to 5% by mass, 0.5% by mass to 3% by mass, or 1% by mass to 3% by mass, based on the total mass of the adsorbent 100a, depending on the thickness and area of ​​the intermediate layer 106. This composition is controlled by adjusting the charge ratio of the materials included in the core 102 and the coating layer 104 to the materials included in the intermediate layer 106 during the manufacture of the adsorbent 100a. The magnesium included in the intermediate layer 106 may be determined from a quantitative value of magnesium obtained using inductively coupled plasma optical emission spectrometry (ICP-OES) or inductively coupled plasma mass spectrometry (ICP-MS). However, when the coating layer 104 includes a magnesium compound, the quantitative value obtained is the quantitative value of magnesium included in the intermediate layer 106 and the coating layer 104.

[0035] 2. Manufacturing method of adsorbent 2 shows a flow chart illustrating a method for producing the adsorbent 100. The adsorbent 100 can be produced by granulating a mixture of a porous carbide obtained by carbonizing an organic substance and a first binder to form a core 102, and then coating the core 102 with a coating layer 104. When an alkaline earth metal compound or iron is contained in the core 102, an alkaline earth metal compound or iron powder is further added to the mixture.

[0036] (1) Preparation of porous carbide Porous carbides are prepared by heating and carbonizing organic matter in an inert gas atmosphere such as argon gas, a low-oxygen atmosphere, a reducing atmosphere, or a reduced pressure atmosphere. 2 Pa or more 10 5 The carbonization may be performed by heating the organic matter at a pressure of 10 Pa or less. Alternatively, the carbonization may be performed by heating at normal pressure under conditions of an oxygen concentration of 0.01% to 3% or 0.1% to 2%. The heating temperature in the carbonization may be 400°C to 1200°C, 500°C to 1100°C, or 600°C to 1000°C. The heating time may be 10 minutes to 10 days, or 10 minutes to 5 hours.

[0037] Carbonization is carried out using an internal combustion or external heat carbonization furnace. Carbonization of biomass generates dry distillation gas, and a porous carbonized material is produced in which pores of various shapes and sizes are formed, which are a complex mixture of pores due to the structure of the biomass and pores formed by desorption of the dry distillation gas. Dry distillation gas mainly contains combustible or reducing gases such as hydrogen, carbon monoxide, and alkanes such as methane, propane, and butane. Dry distillation gas is extracted at high temperatures (700°C to 1300°C), so its thermal energy and combustibility can be used as an energy source for power generation and hot water supply. The porous carbonized material obtained by carbonization is appropriately crushed and processed into powder before the subsequent granulation process. As the porous carbonized material, an irregularly shaped carbonized material obtained by gasification power generation of biomass (waste charcoal from wood biomass gasification power generation) can be used.

[0038] Alternatively, the porous carbonized material constituting the core 102 may be formed by putting an organic material (e.g., biomass) as a raw material into a mold, applying pressure to mold the organic material (pressure molding), and carbonizing the molded organic material to form the core 102. In this case, the shape of the mold is reflected in the shape of the core 102. Therefore, the shape of the inside of the mold may be determined in consideration of the shape of the core 102, and may be, for example, a cylindrical shape with a diameter of 1 mm to 20 mm, 2 mm to 11 mm, or 3 mm to 8 mm, and a height of 1 mm to 20 mm, 3 mm to 15 mm, or 6 mm to 12 mm.

[0039] (2) Mixing / granulation The porous carbide is then mixed with a first binder. If the core 102 contains an alkaline earth metal compound or iron, the alkaline earth metal compound and iron powder are further mixed. When mixing these components, water may be added as needed. Adding water can prevent dust generation and can mix the porous carbide and iron powder more uniformly.

[0040] The mixture of the porous carbide and the first binder may be granulated and molded into a certain shape such as pellets. The granulation may be performed using a compression type granulator, an extrusion type granulator, a roll type granulator, a blade type granulator, a melting type granulator, or a spray type granulator. The porous carbide molded by granulation may be appropriately cured. For example, the curing may be performed by leaving the mixture at rest at a temperature of room temperature or higher and 70° C. or lower for a period of one day or more and one month or less. The core 102 is formed by the above steps.

[0041] (3) Formation of the middle class When the intermediate layer 106 is formed, the intermediate layer 106 is coated on the core 102. For example, the intermediate layer 106 may be formed by mixing magnesium carbonate powder with the core 102. The coating may be performed using a coating device described later. At this time, water or alcohol such as ethanol or isopropyl alcohol may be added as appropriate. Alternatively, the intermediate layer 106 may be formed by preparing a suspension of magnesium carbonate in water or alcohol and spray coating or dip coating the suspension on the core 102.

[0042] Alternatively, the core 102 is mixed with magnesium hydroxide powder to coat the core 102 with magnesium hydroxide. The magnesium hydroxide powder may contain other magnesium compounds (e.g., magnesium oxide, magnesium carbonate, magnesium bicarbonate, magnesium sulfate, etc.). In this case, water or alcohol such as ethanol or isopropyl alcohol may be added as appropriate. Alternatively, a suspension of magnesium hydroxide in water or alcohol may be prepared, and the suspension may be spray-coated or dip-coated onto the core 102 to coat the core 102 with magnesium hydroxide.

[0043] Thereafter, a carbon dioxide-containing gas is supplied to the core 102 on whose surface a thin layer of magnesium hydroxide is formed. The concentration of carbon dioxide in the carbon dioxide-containing gas may be higher than the carbon dioxide concentration in the atmosphere (about 400 ppm), and may be, for example, 1% by volume to 100% by volume, 10% by volume to 100% by volume, 50% by volume to 100% by volume, or 75% by volume to 99% by volume. Therefore, the source of the carbon dioxide-containing gas may be a cylinder or tank filled with carbon dioxide, or a facility that emits a large amount of carbon dioxide (for example, a chemical plant, a waste incineration facility, a thermal power plant, or various other factories). In the latter case, the exhaust gas from the facility, or a purified gas obtained by subjecting the exhaust gas to dedusting, desulfurization, denitrification, or the like, may be used as the carbon dioxide-containing gas.

[0044] The treatment with the carbon dioxide-containing gas may be performed by supplying the carbon dioxide-containing gas at normal pressure to the agitator at a temperature between room temperature and 40°C. Alternatively, the core 102 covered with magnesium hydroxide may be placed in a sealable curing container or curing chamber, and the carbon dioxide-containing gas may be introduced into the curing container or curing chamber. The pressure of the carbon dioxide-containing gas at this time is selected from pressures equal to or higher than atmospheric pressure. Specifically, the pressure of the carbon dioxide-containing gas may be selected from a range of 0.013 MPa to 1.30 MPa. As a result, all or a part of the magnesium hydroxide on the surface of the core 102 reacts with carbon dioxide to give magnesium carbonate, and as a result, the intermediate layer 106 is formed. At this time, a part of the magnesium hydroxide may become magnesium hydrogen carbonate and be included in the intermediate layer 106. By utilizing the reaction between magnesium hydroxide and carbon dioxide, the intermediate layer 106 can be formed without using relatively expensive magnesium carbonate, so that the adsorbent 100 can be manufactured at low cost.

[0045] (4) Formation of coating layer The coating layer 104 can be formed by mixing an additive such as a magnesium compound and a second binder with the core 102. The coating can be performed using a coating device or the like. A schematic side view of a coating device 200 used in the manufacturing method of the adsorbent 100 is shown in FIG. 3A, and a schematic top view of the same is shown in FIG. 3B. The coating device 200 includes a drum 210 and a support portion 220. The support portion 220 supports the drum 210 so that the drum 210 can rotate. The drum 210 rotates about a rotation axis C. The drum 210 has a side portion 212 and a bottom portion 214. The side portion 212 and the bottom portion 214 rotate about the rotation axis C. The rotation direction and rotation speed of the side portion 212 and the bottom portion 214 are controlled independently of each other.

[0046] For example, the additive containing the magnesium compound and the second binder, or a mixture thereof, may be brought into contact with the core 102 while stirring the core 102 in the drum 210 using the coating device 200. At this time, a solvent such as water, alcohol such as ethanol or isopropanol, etc. may be used as appropriate. The additive is preferably added stepwise in multiple batches. The solvent is preferably added stepwise in multiple batches in a mist state. By adding the solvent stepwise in multiple batches in a mist state, the additive can be prevented from coagulating, and the coating layer 104 can be formed uniformly on the surface of the core 102.

[0047] The carbon dioxide-containing gas may be supplied while the additive is in contact with the core 102. The carbon dioxide-containing gas may contain other gases such as air. The concentration of carbon dioxide in the carbon dioxide-containing gas may be higher than the carbon dioxide concentration in the atmosphere (about 400 ppm), and may be, for example, 1% by volume to 100% by volume, 10% by volume to 100% by volume, 50% by volume to 100% by volume, or 75% by volume to 99% by volume. Therefore, the source of the carbon dioxide-containing gas may be a cylinder or tank filled with carbon dioxide, or a facility that emits a large amount of carbon dioxide (for example, a chemical plant, a waste incineration facility, a thermal power plant, or various other factories). In the latter case, the exhaust gas from the facility, or a purified gas obtained by performing dedusting, desulfurization, denitrification, etc. on the exhaust gas, may be used as the carbon dioxide-containing gas. By supplying the carbon dioxide-containing gas while the additive is in contact with the core 102, it is possible to suppress the aggregation of the additive, and it is possible to form the coating layer 104 uniformly. Furthermore, adhesion between the adsorbents 100 via the coating layer 104 can be suppressed.

[0048] The treatment with the carbon dioxide-containing gas in forming the coating layer may be performed, for example, by supplying the carbon dioxide-containing gas at normal pressure to the coating device 200 at a temperature between room temperature and 40°C. The pressure of the carbon dioxide-containing gas at this time is selected from pressures equal to or higher than atmospheric pressure. Specifically, the pressure of the carbon dioxide-containing gas may be selected from a range of 0.013 MPa to 1.30 MPa. As a result, all or a part of the magnesium compound in the additive on the surface of the core 102 reacts with carbon dioxide to give magnesium carbonate, and as a result, the coating layer 104 is formed. At this time, a part of the magnesium compound may become magnesium hydrogen carbonate and be included in the coating layer 104. By including magnesium carbonate in the coating layer 104, peeling of the coating layer 104 can be suppressed.

[0049] The drum 210 can form a vortex flow in the core 102 by rotating the side surface portion 212 and the bottom surface portion 214 in opposite directions. The drum 210 can form a vortex flow in the core 102 by changing the rotation speed of the side surface portion 212 and the bottom surface portion 214. The drum 210 can further form a flow with a high stirring effect by tilting the rotation axis C.

[0050] The drum 210 can control the formation of the coating layer 104 by decreasing the rotation speed of the side surface portion 212 and the bottom surface portion 214 over time. The rotation speed of the side surface portion 212 and the bottom surface portion 214 may be, for example, 60 rpm in the first half and 30 rpm in the second half.

[0051] The rotation axis C of the drum 210 may be tilted over time. In other words, the angle of the rotation axis C with respect to the vertical direction may be increased over time. The angle between the rotation axis C of the side surface portion 212 and the bottom surface portion 214 may be, for example, 30° in the first half and 45° in the second half.

[0052] In one embodiment of the method for producing an adsorbent according to the present invention, a vortex is formed in the core 102 within the drum 210 while the core 102 is being coated, thereby making it possible to suppress agglomeration of the resulting adsorbent 100.

[0053] Alternatively, a dispersion obtained by mixing a mixture of the magnesium compound and the second binder with a solvent may be added to the core 102. Examples of the solvent include the above-mentioned water and alcohol. The coating layer 104 is formed on the surface of the core 102 by spray coating or dip coating the core 102 with the above-mentioned dispersion.

[0054] (5)Curing After the coating layer 104 is formed, curing may be performed as necessary. As with curing after granulation, curing may be performed, for example, by leaving the mixture at rest at a temperature of from room temperature to 50° C. for a period of from one day to one month. Through the above steps, the adsorbent 100 is obtained.

[0055] 3. Water purification using adsorbents The adsorbent 100 has a coating layer 104 having a high magnesium composition on its surface. Phosphorus and nitrogen are typical examples of water pollutants in various water bodies such as rivers, lakes, and oceans, and in purified water ponds. Magnesium reacts with nitrogen (particularly inorganic nitrogen such as ammonia nitrogen) and phosphorus (particularly inorganic phosphorus such as orthophosphate phosphorus and polymerized phosphoric acid) to give magnesium ammonium phosphate. Since magnesium ammonium phosphate is poorly soluble in water, by contacting the adsorbent 100 with water containing phosphorus and nitrogen, the phosphorus and nitrogen in the water can be fixed on the adsorbent 100 as magnesium ammonium phosphate. In other words, the adsorbent 100 functions as an adsorbent capable of removing phosphorus and nitrogen, which are pollutants in various water bodies.

[0056] Furthermore, since the core 102 contains porous carbide, it is possible to adsorb and remove various organic compounds such as trihalomethanes and their precursors, anionic surfactants, and pesticides that may be contained in water. If the core 102 contains iron, the iron reacts with phosphorus, a water pollutant, to give iron phosphate. Since iron phosphate also has low solubility in water, it is taken up into the porous carbide, and as a result, phosphorus is fixed to the adsorbent 100. Therefore, the iron contained in the core 102 can also contribute to the removal of phosphorus, a pollutant in various water areas.

[0057] Water purification using the adsorbent 100 may be performed in a batch or continuous manner. For example, the adsorbent 100 may be filled in a container or bag made of a meshed metal plate, cloth, or the like, and brought into contact with the water to be purified.

[0058] If the coating layer 104 is made of only a mixture of magnesium compound and binder without using the core 102, molding is difficult, and the molded product cannot maintain a certain shape (e.g., spherical, pellet, cylindrical, etc.) in water for a long period of time and quickly disintegrates. Therefore, it cannot function as an adsorbent. In other words, by using the core 102, a structure that contributes to the adsorption of phosphorus and nitrogen can be constructed on the surface.

[0059] 4. Carbon dioxide storage systems A carbon dioxide storage system can be constructed using an adsorbent 100 according to one embodiment of the present invention. Specifically, as shown in Fig. 4, in the manufacture of the adsorbent 100, a porous carbonized material obtained by carbonizing an organic matter such as biomass is one of the raw materials. At this time, by using the dry distillation gas obtained by carbonizing the biomass as an energy source, it is possible to generate electricity, produce hot water, and the like (Fig. 4, (1)).

[0060] The resulting porous carbide is mixed with a first binder and an optional alkaline earth metal compound or iron powder to give a core 102, which is coated with a coating layer 104 to give an adsorbent 100 (FIG. 4, (2)). As described above, the adsorbent 100 improves water quality by adsorbing phosphorus and nitrogen contained in various water bodies and purified water reservoirs, and fixes the phosphorus and nitrogen as magnesium ammonium phosphate or iron phosphate (FIG. 4, (3)). Phosphorus and nitrogen are essential elements for plant growth, and therefore the adsorbent 100 with fixed phosphorus and nitrogen functions as fertilizer when spread on soil, contributing to plant growth. Plants use the phosphorus and nitrogen released from the adsorbent 100 as part of their nutrients and fix carbon dioxide by photosynthesis (FIG. 4, (4)). This provides not only food but also materials such as wood, and the residues of food and materials can be used again as biomass.

[0061] In this way, by applying the embodiment of the present invention, a cycle is established that includes (1) the production of porous charcoal from biomass, (2) the production of adsorbent 100, (3) the production of fertilizer through water quality improvement, and (4) the growth of plants that use this fertilizer and the regeneration of biomass. In this cycle, atmospheric carbon dioxide fixed by plants is used as porous charcoal and is stored in the ground in the form of carbon. Therefore, this cycle is a system that reduces and stores atmospheric carbon dioxide in the ground, which contributes not only to water quality improvement but also to the reduction of atmospheric carbon dioxide.

[0062] The above-described embodiments of the present invention may be combined as appropriate as long as they are not mutually inconsistent. Any embodiment in which a person skilled in the art appropriately adds or deletes components or modifies the design based on each embodiment is also included in the scope of the present invention as long as it includes the gist of the present invention.

[0063] Even if there are other effects and advantages different from those brought about by the respective embodiments described above, those which are clear from the description in this specification or which can be easily predicted by a person skilled in the art are naturally understood to be brought about by the present invention. [Explanation of symbols]

[0064] 100: adsorbent, 102: core, 104: coating layer

Claims

1. 1. A method for producing an adsorbent comprising: mixing a core comprising porous carbide with an additive in the presence of carbon dioxide while incrementally adding atomized solvent to form a coating layer covering at least a portion of the core.

2. The method of claim 1 , wherein the additive comprises a magnesium compound.

3. The method according to claim 2 , wherein the magnesium compound is magnesium hydroxide.

4. The method according to claim 2 , wherein the coating layer contains 1% by mass or more and 30% by mass or less of magnesium based on the total mass of the core and the coating layer.

5. The method according to claim 2, wherein the mixing is performed using a coating device having a drum whose side and bottom parts have the same rotation axis and are independently controlled.

6. The manufacturing method according to claim 5 , wherein the side surface portion and the bottom surface portion rotate at different rotational speeds.

7. The method of claim 5 , wherein the side surface portion and the bottom surface portion rotate in different directions.

8. The method of claim 5 , further comprising decreasing the number of rotations of the side surface portion and the bottom surface portion over time.

9. The method of claim 5 , wherein the angle of the axis of rotation is increased over time.

10. The method of claim 2 , wherein the additive is added in stages.

11. The core further comprises a first binder; The method of claim 2 , wherein the coating layer further comprises a second binder.

12. The method according to claim 2 , wherein the concentration of the carbon dioxide is from 1% by volume to 100% by volume.

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