Adsorbent, method for producing the same, and method for purifying water using the adsorbent

Abstract

To provide an adsorbent capable of efficiently adsorbing phosphorus in water as well as nitrogen.SOLUTION: An adsorbent includes a core containing porous carbide, a first coating layer that covers at least a part of the core and contains magnesium carbonate, and a second coating layer that covers at least a part of the first coating layer and contains an alkaline earth metal compound. The second coating layer may contain an alkaline earth metal in an amount of 1 mass% or more and 30 mass% or less with respect to the total mass of the core, the first coating layer, and the second coating layer.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] One embodiment of the present invention relates to an adsorbent material. Alternatively, one embodiment of the present invention relates to a method for purifying water using the adsorbent material. [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] One of the embodiments of the present invention aims to provide an adsorbent having a novel structure, a method for producing the adsorbent, and a method for purifying water in various water areas using the adsorbent. Alternatively, one of the embodiments of the present invention aims to provide an adsorbent capable of efficiently adsorbing not only phosphorus in water but also nitrogen, and a method for producing the adsorbent. Alternatively, one of the embodiments of the present invention aims to provide a system for improving water quality and simultaneously storing carbon through fixation of atmospheric carbon dioxide. [Means for solving the problem]

[0005] One embodiment of the present invention is an adsorbent. The adsorbent has a core containing a porous carbide, a first coating layer covering at least a portion of the core and containing magnesium carbonate, and a second coating layer covering at least a portion of the first coating layer and containing an alkaline earth metal compound. The second coating layer contains 1% by mass or more and 30% by mass or less of an alkaline earth metal based on the total mass of the core, the first coating layer, and the second coating layer.

[0006] One embodiment of the invention is a method for purifying water, comprising contacting water containing phosphorus and nitrogen with the adsorbent material described above.

[0007] One embodiment of the present invention is a method for producing an adsorbent, which includes carbonizing an organic material to produce a porous charcoal, coating the porous charcoal with magnesium hydroxide and then treating the porous charcoal with a carbon dioxide-containing gas, and coating the porous charcoal that has been treated with the carbon dioxide-containing gas with an alkaline earth metal compound. [Brief description of the drawings]

[0008] [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. [Diagram 2] 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

[0009] 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.

[0010] 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.

[0011] 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.

[0012] Hereinafter, an adsorbent according to one embodiment of the present invention and a method for producing the adsorbent, a water purification method using the adsorbent, and a carbon dioxide storage system using the adsorbent will be described. 1. Structure of the adsorbent (1) Overall structure A schematic perspective view of the adsorbent 100 is shown in FIG. 1A, and a schematic view of an end surface perpendicular to the length direction is shown in FIG. 1B. As shown in these figures, the adsorbent 100 basically comprises a core 102, a first coating layer 104 covering the core 102, and a second coating layer 106 covering the first coating layer 104. The first coating layer 104 may cover the entire surface of the core 102, or may cover only a portion of the surface of the core 102 (not shown). Similarly, the second coating layer 106 may cover the entire surface of the first coating layer 104, or may cover only a portion of the surface of the first coating layer 104. Thus, a portion of the core 102 may be exposed from both the first coating layer 104 and the second coating layer 106, or may be in direct contact with the second coating layer 106. A portion of the first coating layer 104 may also be exposed from the second coating layer 106.

[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. The porous carbide is a carbide 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 the organic matter is biomass. Here, biomass refers to substances derived from living organisms and their metabolites. Specifically, examples of the biomass include plank-shaped or column-shaped wood, thinning wood, pruning waste, construction waste wood, powdered sawdust, particle boats, and other wooden molded products. There is no restriction on the type of wood, and it may be cedar, cypress, or bamboo. Alternatively, agricultural waste such as rice husks, bagasse, corn cobs and leaves, and agricultural by-products such as straw, wheat straw, and hay are also examples of biomass. Alternatively, examples of the biomass include plants that are the raw material for fibers such as hemp, flax, cotton, sisal, abaca, and coconut hair. Alternatively, it may be algae such as seaweed. Alternatively, food waste, silage obtained from animal manure, etc. can be used. As described later, by using biomass as a raw material for porous charcoal, a system for storing carbon dioxide from the atmosphere can be constructed.

[0016] (3) First Coating Layer The first coating layer 104 is a layer containing magnesium carbonate. There is no restriction on the thickness of the first coating layer 104, 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 first coating layer 104 may contain other magnesium compounds such as magnesium hydroxide, magnesium oxide, magnesium hydrogen carbonate, and magnesium sulfate in addition to magnesium carbonate.

[0017] By covering the entire or part of the core with the first coating layer 104, the second coating layer 106 can be formed uniformly on the first coating layer 104, and peeling in water can be prevented.

[0018] (4) Second Coating Layer The second coating layer 106 includes an alkaline earth metal compound. The second coating layer 106 may further include a binder and / or iron. There is no restriction on the thickness of the second coating layer 106, 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 second coating layer 106, which contributes to the adsorption of phosphorus and nitrogen in water, is thicker than the first coating layer 104.

[0019] Examples of the alkaline earth metal compound include magnesium compounds and calcium compounds, such as hydroxides, sulfates, carbonates, hydrogencarbonates, and oxides of magnesium or calcium. The second coating layer 106 may contain one or more of the above alkaline earth metal compounds. Among these alkaline earth metal compounds, magnesium hydroxide, magnesium oxide, or magnesium carbonate is preferred because they are inexpensive, the second coating layer 106 can be easily formed, and they have high adhesion to the core 102 and the first coating layer 104.

[0020] The binder, which is an optional component, functions as an auxiliary component for forming the second coating layer 106. As the 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, blast furnace slag powder, fly ash, gypsum (calcium sulfate), calcined gypsum obtained by heating and dehydrating gypsum, sodium silicate, etc. can be mentioned. In particular, inorganic binders are preferable because they are highly weather resistant, 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.

[0021] Iron, which is an optional component, is added to the second coating layer 106 as iron powder. Therefore, the second coating layer 106 may contain iron oxide or iron hydroxide generated by surface oxidation, along with zero-valent iron. The iron in the iron oxide and iron hydroxide may be divalent or trivalent. Also, iron may exist in a mixed valence state. Therefore, examples of 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 second coating layer 106 may contain sulfur, phosphorus, manganese, silicon, vanadium, copper, and 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%.

[0022] 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 second coating layer 106. 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.

[0023] (5) Composition The porous carbide, which is the basic skeleton of the core 102, is contained in the adsorbent 100 in a composition of 50% by mass to 99% by mass, 50% by mass to 90% by mass, or 60% by mass to 90% by mass, based on the dry mass of the adsorbent 100 (i.e., the total mass of the core 102, the first coating layer 104, and the second coating layer 106 excluding water, which is taken as 100% by mass). By adopting the above composition, the core 102 can be formed with light weight and sufficient strength. The composition of the porous carbide is controlled by adjusting the charge ratio of the materials constituting the first coating layer 104 and the second coating layer 106 to the porous carbide 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, for example, combustion and infrared absorption.

[0024] The composition of magnesium carbonate contained in the first coating layer 104 depends on the thickness and area of ​​the first coating layer 104, but 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, relative to the total mass of the adsorbent 100. This composition is controlled by adjusting the charge ratio of the materials constituting the core 102 and the second coating layer 106 to the materials constituting the first coating layer 104 during the manufacture of the adsorbent 100. The magnesium contained in the first coating layer 104 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 second coating layer 106 contains a magnesium compound, the quantitative value obtained is the quantitative value of magnesium contained in the first coating layer 104 and the second coating layer 106.

[0025] The composition of the alkaline earth metal contained in the second coating layer 106 depends on the thickness and area of ​​the second coating layer 106, but may be, for example, 1% by mass to 30% by mass, 1% by mass to 20% by mass, or 50% by mass to 10% by mass, relative to the total mass of the adsorbent 100. Alternatively, the alkaline earth metal compound may be contained in the second coating layer 106 at a composition of 1% by mass to 30% by mass, 5% by mass to 30% by mass, or 5% by mass to 25% by mass, relative to the mass of the adsorbent 100. This composition is controlled by adjusting the charge ratio of the materials contained in the core 102 and the first coating layer 104 to the second coating layer 106 during the manufacture of the adsorbent 100. The alkaline earth metal contained in the second coating layer 106 may be determined from a quantitative value obtained using ICP-OES, ICP-MS, or the like. However, when the second coating layer 106 contains magnesium, the quantitative value of magnesium is the quantitative value of magnesium contained in the first coating layer 104 and the second coating layer 106.

[0026] The binder is contained in the second coating layer 106 in a composition of 1% by mass to 30% by mass, 1% by mass to 20% by mass, or 5% by mass to 20% by mass with respect to the total mass of the adsorbent 100. By adopting the above composition, the second coating layer 106 can be easily formed, and the second coating layer 106 having high adhesive strength with the first coating layer 104 or the core 102 can be formed. The composition of the binder is controlled by adjusting the charge ratio during the manufacture of the adsorbent 100. The composition of the binder may also be determined from measured values. For example, when the binder contains calcium sulfate, the composition may be determined from a quantitative value of sulfur obtained using ICP atomic emission spectrometry (ICP-AES) or a combustion-infrared absorption method, or a quantitative value of calcium obtained using atomic absorption spectrometry (AAS), ICP-OES, potassium permanganate volumetric method, or the like. When the second coating layer 106 contains gypsum as a binder and calcium as an alkaline earth metal, the quantitative value of calcium is the quantitative value of calcium contained in the alkaline earth metal and the binder.

[0027] When second coating layer 106 contains iron, the iron content is, for example, 1% by mass to 10% 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 by, for example, ICP-OES or ICP-MS.

[0028] 2. Manufacturing method of adsorbent The adsorbent 100 can be manufactured by preparing a porous carbonized material obtained by carbonizing an organic substance, and then successively forming the first coating layer 104 and the second coating layer 106 thereon.

[0029] (1) Preparation of porous carbide The porous charcoal constituting the core 102 can be prepared by carbonizing an organic material (e.g., biomass) as a raw material. For example, the core 102 can be prepared by putting the organic material into a mold, applying pressure to mold the organic material (pressure molding), and carbonizing the molded organic material. 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.

[0030] The molded organic material is heated and carbonized in an inert gas atmosphere such as argon gas, a low-oxygen atmosphere, a reducing atmosphere, or a reduced pressure atmosphere to form the core 102. 2 Pa or more 10 5The 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.

[0031] Carbonization is carried out using an internal combustion or external heat carbonization furnace. Carbonization of biomass generates pyrolysis gas, and produces a porous carbonized material with pores of various shapes and sizes, which are a complex mixture of pores due to the structure of the biomass and pores formed by the desorption of pyrolysis gas. The pyrolysis gas mainly contains flammable or reducing gases such as hydrogen, carbon monoxide, and alkanes such as methane, propane, and butane. Since pyrolysis gas is extracted at a high temperature (700°C to 1300°C), its thermal energy and flammability can be used as an energy source for power generation, hot water supply, etc.

[0032] Alternatively, a carbide of an irregular shape obtained by gasification power generation of biomass (waste coal from woody biomass gasification power generation) may be put into a mold and compression molded. When the porous carbide contains pellet-shaped porous carbide, the porous carbide may be crushed into powder, and then the powdered porous carbide may be put into a mold and compression molded. In this case, the shape of the mold also determines the shape of the core 102, so a mold having a cylindrical internal structure of the above-mentioned size may be used.

[0033] (2) Formation of the first coating layer Thereafter, the core 102 is coated with the first coating layer 104. For example, the first coating layer 104 may be formed by mixing magnesium carbonate powder with the core 102. At this time, water or alcohol such as ethanol or isopropyl alcohol may be added as appropriate. Alternatively, the first coating layer 104 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.

[0034] 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.

[0035] 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.

[0036] 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 coated 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 first coating layer 104 is formed. At this time, a part of the magnesium hydroxide may become magnesium hydrogen carbonate and be included in the first coating layer 104. By utilizing the reaction between magnesium hydroxide and carbon dioxide, the first coating layer 104 can be formed without using relatively expensive magnesium carbonate, so that the adsorbent 100 can be manufactured at low cost.

[0037] In the method described above, the first coating layer 104 is formed by reaction of magnesium hydroxide on the core 102 with carbon dioxide, but magnesium hydroxide may be supplied to the core 102 while a carbon dioxide-containing gas is supplied to the agitator.

[0038] (3) Formation of the second coating layer The second coating layer 106 can be formed by mixing the core 102 on which the first coating layer 104 is formed with a powder of an alkaline earth metal compound. For example, the alkaline earth metal compound may be brought into contact with the core 102 while stirring the core 102. When the second coating layer 106 contains a binder and / or iron, the binder and / or iron powder may be further added and the mixture may be stirred. At this time, water or an alcohol such as ethanol or isopropyl alcohol may be added as appropriate.

[0039] Alternatively, an alkaline earth metal compound, or a mixture of an alkaline earth metal compound and a binder, a mixture of an alkaline earth metal compound and iron powder, or a mixture of an alkaline earth metal compound, a binder, and an iron powder may be mixed with a solvent such as water or an alcohol such as ethanol or isopropanol to prepare a dispersion, and the dispersion may be spray-coated or dip-coated onto the core 102 on which the first coating layer 104 is formed to form the second coating layer 106. After the second coating layer 106 is formed, curing may be performed as necessary. For example, curing may be performed by leaving the core 102 at rest at a temperature of room temperature or higher and 50° C. or lower for a period of one day to one month. The above steps result in the adsorbent 100.

[0040] 3. Water purification using adsorbents The adsorbent 100 includes a porous carbide in the core 102, and further includes a second coating layer 106 containing an alkaline earth metal compound on the surface. Phosphorus and nitrogen are typical examples of water pollutants in various water areas such as rivers, lakes, and seas, and purified water ponds. Magnesium and calcium, which are alkaline earth metals, react 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 and calcium ammonium phosphate, respectively. Since magnesium ammonium phosphate and calcium ammonium phosphate are 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 or calcium ammonium phosphate. In other words, the adsorbent 100 functions as an adsorbent capable of removing phosphorus and nitrogen, which are pollutants in various water areas.

[0041] Furthermore, since the core 102 contains porous carbide, it is possible to adsorb and remove trihalomethanes and their precursors, anionic surfactants, various organic compounds such as pesticides, etc. that may be contained in water. When the second coating layer 106 contains iron, the iron reacts with phosphoric acid, 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 second coating layer 106 can also contribute to the removal of phosphorus, which is a pollutant in various water areas.

[0042] 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.

[0043] As described above, the adsorbent 100 has the first coating layer 104 containing magnesium carbonate between the core 102 and the second coating layer 106. Therefore, the second coating layer 106 shows high affinity to the first coating layer 104. This can prevent the second coating layer 106 from peeling off in water. Also, as described above, the core 102 is formed by carbonizing an organic material that has been molded under pressure in advance, or by pressure molding a powdered carbonized material, so that the shape stability in water is high. Therefore, the disintegration or decomposition of the adsorbent 100 in water is slow, and the adsorbent 100 can be in contact with water for a long period of time. Therefore, the adsorbent 100 can function as an adsorbent that can be used for a long period of time.

[0044] 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. 2, in the production of the adsorbent 100, a porous carbonized material obtained by carbonizing an organic matter such as biomass functions as a core 102. At this time, by using 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. 2, (1)).

[0045] The core 102 is coated with magnesium carbonate and further coated with a second coating layer 106 containing an alkaline earth metal to give the adsorbent 100 (FIG. 2, (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, calcium ammonium phosphate, or iron phosphate (FIG. 2, (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 through photosynthesis (FIG. 2, (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.

[0046] 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. [Explanation of symbols]

[0047] 100: Adsorbent, 102: Core, 104: First coating layer, 106: Second coating layer

Claims

1. A core comprising a porous carbide; a first coating layer covering at least a portion of the core and comprising magnesium carbonate; and a second coating layer covering at least a portion of the first coating layer and including an alkaline earth metal compound; The adsorbent, wherein the second coating layer comprises from 1% by weight to 30% by weight of an alkaline earth metal based on the total weight of the core, the first coating layer, and the second coating layer.

2. The adsorbent according to claim 1 , wherein the porous charcoal is contained in a composition of 50 mass % or more and 99 mass % or less with respect to the total mass.

3. The adsorbent of claim 1 , wherein the second coating layer further comprises 5% by weight to 30% by weight of a binder, based on the total weight.

4. 4. The adsorbent material of claim 3, wherein the binder comprises a material selected from sodium silicate, potassium silicate, silicon oxide, gypsum, and cement.

5. 2. The adsorbent of claim 1, wherein the second coating layer further comprises from 5% to 15% by weight of iron based on the total weight.

6. 10. The adsorbent of claim 1, wherein the alkaline earth metal compound comprises one or more compounds selected from magnesium hydroxide, magnesium oxide, magnesium sulfate, calcium hydroxide, calcium oxide, and calcium sulfate.

7. A method for purifying water, comprising contacting water containing phosphorus and nitrogen with the adsorbent of claim 1.

8. Carbonizing the organic matter to produce a porous charcoal; coating the porous carbide with magnesium hydroxide and then treating it with a carbon dioxide-containing gas; and coating the porous charcoal treated with the carbon dioxide-containing gas with an alkaline earth metal compound.

9. The method of claim 8 , wherein the coating of the alkaline earth metal compound is performed by mixing the porous carbide with the alkaline earth metal compound.

10. The method of claim 8 , wherein the coating of the alkaline earth metal compound is performed by mixing the porous carbide with the alkaline earth metal compound and a binder.

11. The method according to claim 8, wherein the alkaline earth metal compound is magnesium hydroxide.

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