JP2022138628A - Adsorbent and method for producing the same - Google Patents

Abstract

To provide an adsorbent which can be used for water quality improvement, has low ignitability, and can be safely treated, and a method for producing the same.SOLUTION: An adsorbent has a core containing a porous carbide, a binder and iron powder, and a coating layer covering at least a part of the core. The adsorbent can have a pellet shape with a length to a diameter of 0.5 or more and 5 or less and the diameter of 1 mm or more and 20 mm or less. The coating layer may include a material selected from sodium silicate, potassium silicate, a silicon oxide, a resin, iron powder, gypsum and cement.SELECTED DRAWING: Figure 1

Description

One embodiment of the present invention relates to an adsorbent and method of making the same.

An adsorbent made of iron supported on a porous carbide having carbon prepared from biomass as a basic material can adsorb phosphate ions derived from phosphoric acid. It is known that it can be used to improve water quality in water areas. In addition, since the adsorbent that adsorbs phosphate ions can also be used as fertilizer, by spraying the adsorbent after adsorbing phosphate ions on the soil, the carbon dioxide fixed by the plants can be effectively used. , it becomes possible to store carbon dioxide in the soil. Biomass-derived adsorbents therefore play a central role in carbon storage for fixing greenhouse gases in the atmosphere (see Patent Document 1 and Non-Patent Document 1).

JP-A-2007-75706

Akira Shibata, "Simple carbonization of biomass and carbon-storing vegetables COOL VEGETM for regional development", Journal of High Temperature Society, March 2011, Vol. 37, No. 2, p. 37-42

An object of one of the embodiments of the present invention is to provide an adsorbent and a manufacturing method thereof. Another object of one of the embodiments of the present invention is to provide an adsorbent that can be used for improving water quality, has low flammability, and can be safely handled, and a method for producing the same. Another object of one of the embodiments of the present invention is to provide an adsorbent that can be used to improve water quality and can maintain its shape in water for a long period of time, and a method for producing the same. Alternatively, it is an object of one embodiment of the present invention to provide a system for sequestering carbon through atmospheric carbon dioxide fixation.

One of the embodiments of the invention is an adsorbent. The adsorbent has a core comprising porous carbide, a binder, and iron powder, and a coating layer covering at least a portion of the core.

One embodiment of the present invention is a method of making an adsorbent. The manufacturing method includes mixing a porous carbide with a binder and iron powder to form a mixture, and forming a coating layer over at least a portion of the mixture.

According to the embodiments of the present invention, it is possible to provide an adsorbent that exhibits long-term effectiveness in improving the water quality of water areas such as rivers, lakes, and the sea, and that is highly safe, and a method for producing the same. In addition, it becomes possible to produce a fertilizer effective for growing plants at a low cost. Furthermore, carbon dioxide in the atmosphere can be stored underground in the form of carbon, contributing to the suppression of the greenhouse effect.

1A and 1B are a schematic perspective view and an end view of an adsorbent according to one embodiment of the present invention; FIG. 4 is a flow chart showing a method for manufacturing an adsorbent according to one embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS The conceptual diagram which shows the carbon dioxide storage system which is one of the embodiment of this invention.

Hereinafter, each embodiment of the present invention will be described with reference to the drawings. However, the present invention can be implemented in various aspects without departing from the gist thereof, and should not be construed as being limited to the description of the embodiments illustrated below.

In order to make the description clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual embodiment, but this is only an example and does not limit the interpretation of the present invention. not something to do.

In this specification and claims, the expression "a structure is exposed from another structure" means that a part of a structure is not covered by another structure. The portion not covered by the structure also includes a mode covered by another structure.

<First embodiment>
In this embodiment, an adsorbent 100 according to one embodiment of the present invention and a manufacturing method thereof will be described.
1. Adsorbent 1-1. Structure A schematic perspective view of the adsorbent 100 is shown in FIG. 1(A), and a schematic view of an end face perpendicular to the length direction is shown in FIG. 1(B). As shown in these figures, the adsorbent 100 basically comprises a core 102 and a coating layer 104 covering the core 102 .

The shape of the adsorbent 100 is arbitrary, and may be a plate shape, a spherical shape, or a so-called pellet shape as shown in FIG. 1(A). In the case of a pellet shape, as shown in FIG. 1B, the shape of the adsorbent 100 may be a cylinder, and although not shown, it may be an elliptical cylinder, a triangular cylinder, a square cylinder, a pentagonal cylinder, a hexagonal cylinder, or the like with polygonal end faces ( prism) may be used. Also, the adsorbent 100 may have a partially deficient cylindrical, elliptical, or prismatic shape.

When the adsorbent 100 is cylindrical, 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. Alternatively, the end face area of the adsorbent 100 may be 0.8 mm ² or more and 300 mm ² or less. The aspect ratio of the adsorbent 100, that is, the ratio of the length L to the diameter D (L/D) is also arbitrary, and can be, for example, 0.5 or more and 5 or less. Specifically, the length L can be 1 mm or more and 20 mm or less, 3 mm or more and 15 mm or less, or 6 mm or more and 12 mm or less.

The core 102 is a structure for exhibiting the function of the adsorbent 100, and has a porous carbide as a basic skeleton. On the other hand, the coating layer 104 has a configuration that contributes to improving the safety of the adsorbent 100 by imparting physical strength to the core 102 and reducing ignitability. The coating layer 104 may be provided so as to cover the entire surface of the core 102, or as shown in FIG. It may be provided so as to be exposed from the coating layer 104 .

1-2. Core The core 102 includes porous carbide, iron (zero-valent iron) supported on its surface and pores, and a binder. Due to the supported iron, phosphoric acid present in water and its ions become iron phosphate, which is adsorbed on the porous carbide. Therefore, this adsorbent 100 can be used as an adsorbent for effectively improving the water quality of water areas such as rivers, lakes, and seas. The adsorbent 100 may contain iron compounds and may also contain compounds of metals selected from alkali metals and alkaline earth metals. Also, the adsorbent 100 may further contain water as another component.

(1) Porous charcoal The porous charcoal is a charcoal produced by using an organic substance as a raw material and heating and carbonizing the organic substance under conditions of low oxygen concentration. A biomass is illustrated as an organic matter. Porous charcoal derived from biomass includes charcoal, bamboo charcoal, white charcoal, black charcoal, sawdust charcoal, coconut charcoal, and rice husk charcoal. As will be described later, by using biomass as a raw material for porous charcoal, it is possible to construct a system for storing carbon dioxide in the atmosphere, and it works as a reaction site to prevent the adsorbent 100 from collapsing in water. Alkali metal and alkaline earth metal ions can be provided.

Carbonization is performed by heating the organic matter in an inert gas atmosphere such as nitrogen gas or argon gas, an oxygen-free atmosphere, a low-oxygen atmosphere, a reducing atmosphere, or a reduced-pressure atmosphere. When carbonization is performed in a reduced pressure atmosphere, a low vacuum state of 10 ² Pa or more and 10 ⁵ Pa or less, a medium vacuum state of 10 ⁻¹ Pa or more and 10 ² Pa or less, and a high vacuum state of 10 ⁻⁵ Pa or more and 10 ⁻¹ Pa or less. , or in an ultra-high vacuum state of 10 ⁻⁵ Pa or less. When carbonization is performed in a low-oxygen atmosphere, the oxygen concentration can be 0.01% or more and 3% or less, or 0.1% or more and 2% or less. The heating temperature for carbonization may be 400° C. or higher and 1200° C. or lower, 500° C. or higher and 1100° C. or lower, 600° C. or higher and 1000° C. or lower, or 600° C. or higher and 900° C. or lower. The heating time may be 10 minutes or more and 10 days or less, or 10 minutes or more and 5 hours or less.

Carbonization is carried out using internal combustion or externally heated carbonization furnaces. Examples of the carbonization furnace include a batch-type closed coal kiln, a continuous rotary kiln, an oscillating carbonization furnace, and a screw furnace. Carbonization of biomass generates dry distillation gas, and pores with various shapes and sizes are formed, which are a complex mixture of pores caused by the structure of biomass and pores formed by desorption of dry distillation gas. A fine porous carbide is produced. Carbonized gases mainly include combustible or reducing gases such as hydrogen, carbon monoxide, methane, propane, and alkanes represented by butane. Since the dry distillation gas is taken out at a high temperature (700° C. to 1300° C.), its thermal energy and combustibility can be used as an energy source for power generation and hot water supply.

Here, biomass refers to substances derived from living organisms and their metabolites, which are a kind of organic matter. Examples of biomass include materials derived from trees. Specific examples include wood products such as plate-like or column-like wood, thinning wood, pruning waste wood, construction waste wood, powdered sawdust, and particle boats. There are no restrictions on the type of wood, and cedar, cypress, and bamboo may 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, straw, and hay. Other examples include plants used as raw materials for fibers such as hemp, flax, cotton, sisal, abaca, and palm hair. Alternatively, algae such as seaweed may be used. Other examples include food waste and silage obtained from animal manure.

The size and shape of the porous carbide are not particularly limited, but the average particle size may be 1 μm or more and 50 mm or less or 1 μm or more and 1 mm or less. By having the average particle diameter within this range, the porous carbide and the iron powder can be uniformly mixed in the later-described mixing and kneading steps.

Due to the pores formed inside, the porous carbide has a large specific surface area. Specifically, the specific surface area of the porous carbide is 100 m ² /g or more and 900 m ² /g or less, or 100 m ² /g or more and 800 m ² /g or less, or 150 m ² /g or more and 400 m ² /g or less. be. The specific surface area is measured using a mercury intrusion method, a gas adsorption method exemplified by the BJH method or the HK method, or the like.

(2) Iron and Iron Compound As will be described later, iron is mixed with porous carbide as iron powder and supported. There are no restrictions on the shape of the iron powder. For example, an iron powder having an average circularity of 50 to 100, 70 to 95, or 80 to 90 may be used. Here, the average circularity is one of the parameters representing the shape of each iron particle contained in the iron powder, and the image obtained by microscopic observation of the iron powder is analyzed to obtain the circularity of multiple iron particles. , which is the average value. As the degree of circularity, for example, a value obtained by dividing the perimeter of a circle having an area equal to the area of the projection plane by the perimeter of the projection plane of each iron particle in the microscope image can be used. Alternatively, a value obtained by dividing the area of the projection plane by the area of the circle inscribed in the projection plane may be employed as the degree of circularity.

There are no restrictions on the average particle size of the iron powder. For example, the iron powder may have an average particle size in the range of 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 microscopic observation of the iron powder, determining the particle size of a plurality of iron particles, and averaging the obtained values. As the particle diameter of each iron particle, for example, the diameter of a circle or the length of one side of a square inscribed in the projected plane of each iron particle in a microscope image can be used.

The iron powder may contain trace amounts of other elements. Other elements include carbon, oxygen, sulfur, phosphorus, manganese, silicon, vanadium, copper and titanium. Therefore, the purity of the iron powder may be 90.0% or more and 99.9% or less or 95.0% or more and 99.0% or less.

Incidentally, part of the iron powder may be carried on the porous carbide in an oxidized state, that is, as an iron compound. Iron compounds include iron oxide and iron hydroxide. The iron contained in the iron compound may exist in a state of divalent, trivalent, or a mixed valence in which divalent and trivalent valences are mixed. Therefore, when the iron compound is iron hydroxide, it may be ferrous hydroxide or ferric hydroxide. When the iron compound is iron oxide, it may be wustite (FeO), hematite or maghemite _{( Fe2O3} ), or magnetite _{( Fe3O4} ).

(3) Binder The binder is used to efficiently disperse the porous carbide and the iron powder in the kneading step, which will be described later, and integrate iron and iron compounds with the porous carbide. Although there are no restrictions on the type of binder, an organic binder and/or an inorganic binder can be used. Examples of organic binders include molasses, blackstrap molasses, starch, dextrin, corn starch, rice bran, polyvinyl alcohol, copolymers of vinyl acetate and ethylene or saponified products thereof, pulp waste liquid, ligninsulfonate, carboxymethylcellulose, hydroxypropyl. One or more selected from methylcellulose, sodium alginate, phenolic resin, tar pitch, and the like. Among them, molasses is inexpensive, contains few harmful components, and contains many solid components. Examples of inorganic binders include cement, ground granulated blast furnace slag, fly ash, gypsum (calcium sulfate), calcined gypsum obtained by heating and dehydrating gypsum, and sodium silicate.

(4) Compounds of alkali metals and alkaline earth metals Compounds of metals selected from alkali metals and alkaline earth metals include halides, oxides and hydroxides of sodium, potassium, lithium, cesium, magnesium, and calcium. substances, sulfates, nitrates, carbonates, and bicarbonates. These compounds may be added during the production of the adsorbent 100, but when biomass is used as the raw material for the porous carbide, they may be alkali metal or alkaline earth metal compounds contained in the biomass.

When the alkali metal or alkaline earth metal compounds are carbonates or hydrogen carbonates, for example hydroxides, chlorides or oxides of alkali metals or alkaline earth metals contained in or added to porous carbides Carbonate or bicarbonate obtained by reaction (hereinafter referred to as carbonation) of carbon dioxide, sulfate, or nitrate with carbon dioxide may also be used.

(5) Composition ratio The composition ratio of the configuration described above can be adjusted as appropriate. For example, the content of porous carbide in the adsorbent 100 may be adjusted in the range of 20% to 80% by mass, 40% to 80% by mass, or 60% to 80% by mass. The iron powder content may be adjusted in the range of 5% to 35% by mass, 5% to 25% by mass, or 5% to 20% by mass. The content of the binder may be adjusted in the range of 5% by mass to 50% by mass, 15% by mass to 50% by mass, or 20% by mass to 50% by mass. The sum of the contents of alkali metals and alkaline earth metals may be adjusted in the range of 1% to 30% by mass, 1% to 15% by mass, or 1% to 10% by mass.

Alternatively, the content of carbon in the adsorbent 100 may be adjusted within the range of 10% by mass or more and 80% by mass or less. The content of iron (that is, an iron element containing zero-valent iron and iron ions) in the adsorbent 100 may be adjusted within a range of 5% by mass or more and 35% by mass or less. In addition, the sum of the contents of alkali metals and alkaline earth metals may be adjusted within the range of 1% by mass or more and 30% by mass or less.

In measuring the content of porous carbide in the adsorbent 100, first, the carbon content of the porous carbide in the raw material stage is measured. For example, a method based on JIS H1617, JIS Z2615, and ASTM E1941 may be adopted using a combustion/infrared absorption method. Specifically, the porous carbide in the raw material stage is burned in a combustion furnace under an oxygen stream to generate carbon dioxide. The concentration of carbon dioxide is determined by introducing the produced carbon dioxide into an infrared spectrometer using oxygen gas and measuring its absorption with a detector. From this concentration of carbon dioxide, the mass of carbon in the porous carbide in the raw material stage is quantified as the mass of the porous carbide. After that, the content of the porous carbide may be determined from the mass of the porous carbide in the raw material stage, the binder mixed with the porous carbide, iron powder, water, and other raw materials. The content of iron powder and binder may also be calculated from the masses of iron powder, binder, porous carbide, water, etc. used in the manufacturing process of the adsorbent 100 .

In the above-described method, the reaction rate of alkali metal or alkaline earth metal hydroxides, chlorides, oxides, sulfates, or nitrates with carbon dioxide and the change in mass of the adsorbent 100 due to this reaction are considered. not. It also does not take into account the formation of iron compounds due to the oxidation of iron in the manufacturing process. However, since the mass change caused by these reactions is in a negligible range, it can be said that the reliability of the measurement results obtained by the above method is sufficiently high.

The sum of the contents of metals selected from alkali metals and alkaline earth metals can be determined by, for example, inductively coupled plasma optical emission spectroscopy (ICP-OES) or inductively coupled plasma mass spectrometry (ICP-MS) for the adsorbent 100. It can be measured by applying In ICP-OES, an argon plasma is used as a light source, and an atomized solution sample is introduced into the plasma. Metals and alkaline earth metals can be quantified. ICP-MS is a method in which argon plasma is used as an ion source, elements contained in a sample are ionized, and the ions are separated and detected based on the mass-to-charge ratio. The element can be identified from the mass-to-charge ratio of the detected ions, and the alkali metals and alkaline earth metals can be quantified by counting the detected ions.

On the other hand, the content of carbon in the adsorbent 100 can be obtained by applying the combustion/infrared absorption method to the adsorbent 100 . The content of carbon in the adsorbent 100 is the content of carbon mainly derived from the binder, carbonates and hydrogencarbonates of metals selected from alkali metals and alkaline earth metals in the porous carbide. . The iron content and the sum of the alkali metal and alkaline earth metal content can also be measured by applying ICP-OES or ICP-MS to the adsorbent 100 .

1-3. Coating Layer Coating layer 104 covers all or part of core 102 . The coating layer 104 contains, for example, an inorganic compound such as sodium silicate, calcium silicate, or silicon oxide, or resin. Iron powder, gypsum (calcium sulfate), and cement may be used as inorganic compounds. Examples of resins include acrylic resins, epoxy resins, polylactic acid, polystyrene, polyethylene, and polyesters. Preferably, an inorganic compound that has a low impact on the natural environment is used. The coating layer 104 can have a thickness of, for example, 10 μm to 1 mm, 50 μm to 500 μm, or 100 μm to 300 μm.

The coating layer 104 may be composed of a single layer, or a plurality of layers containing different materials may be laminated to form the coating layer 104 .

When the raw material of the coating layer 104 is liquid, the coating layer 104 may be formed by applying the raw material of the coating layer 104 to the core 102 by spray coating, dip coating, or the like. Liquid raw materials include aqueous solutions of sodium silicate and potassium silicate, and alcohol solutions of tetraalkoxysilanes such as tetramethoxysilane and tetraethoxysilane. When tetraalkoxysilane is used as a raw material, the tetraalkoxysilane is rapidly hydrolyzed and condensed by water in the atmosphere to form a silicon oxide film. When the coating layer 104 contains a resin, the coating layer 104 can be formed by applying a monomer or oligomer as a raw material and then polymerizing or cross-linking it by heating or light irradiation. Alternatively, the coating layer 104 may be formed by applying a solution of a polymer as a raw material and then distilling off the solvent.

When the raw material of the coating layer 104 is solid, the coating layer 104 may be formed by spraying water or alcohol on the core 102 and contacting the raw material of the coating layer 104 in that state.

By covering the surface of core 102 with coating layer 104 , physical strength is imparted to adsorbent 100 . For this reason, even if the adsorbent 100 is placed in water for a long period of time to improve the water quality of water areas such as rivers, lakes, and seas, the adsorbent 100 is prevented from being eroded and collapsed by water, and can be used for a long period of time. It can function as an adsorbent over a long period of time.

Moreover, by forming the coating layer 104 within the thickness range described above, the water to be treated can diffuse in the coating layer 104 and come into contact with the core 102 . Moreover, by partially covering the surface of the core 102 so that a part of the surface is exposed, the water to be treated can come into direct contact with the core 102 . Therefore, even if the coating layer 104 is provided, the function of the core 102 as an adsorbent is not impaired.

The phosphate adsorption capacity of the adsorbent 100 can be tested, for example, by a batch test. The batch test is a method of calculating the adsorption amount of phosphoric acid from the difference between the phosphoric acid concentration of the solution containing phosphoric acid, which is the material to be adsorbed, and the phosphoric acid concentration of the supernatant after phosphoric acid has been adsorbed. The concentration of phosphoric acid can be determined using, for example, the molybdenum blue method or the ammonium vanadomolybdate absorbance method. In the former, potassium peroxodisulfate solution is added to a certain amount of the collected sample and heated, and then a mixed solution of ammonium molybdate and bis[(+)-tartrate]diantimonate(III) dipotassium trihydrate is added. In addition, it produces molybdophosphate. A solution of L-ascorbic acid is added to the molybdophosphate to form molybdenum blue (a hydrated mixed valence oxide of molybdenum). Water-soluble phosphate is quantified by measuring the absorption of molybdenum blue (eg, at 880 nm) using a UV-visible spectrophotometer. In the latter, nitric acid (1+1) is added to a certain amount of the collected sample and heated to hydrolyze non-orthophosphoric acid to orthophosphate ions. Thereafter, ammonium vanadate (V), hexaammonium heptamolybdate and nitric acid are added to form phosphovanadomolybdate. Phosphate is quantified by measuring the absorption of phosphovanadomolybdate (eg, at 420 nm) using a UV-visible spectrophotometer.

2. Manufacturing Method An example of a method for manufacturing the adsorbent 100 will be described below. FIG. 2 shows a flow chart showing the method of manufacturing the adsorbent 100 .

2-1. Mixing and Kneading As shown in FIG. 2, first, the raw material porous carbide, binder, and iron (iron powder) are mixed and then kneaded (kneaded). As the porous charcoal, it is preferable to use the charcoal obtained by carbonizing biomass, as described above. The amounts of the porous carbide, binder, and iron powder are appropriately adjusted so that the composition ratio within the range described above is obtained. The porous carbide may be crushed or classified in advance to adjust its particle size. Since the particle size of the porous carbide is often larger than the particle size of the iron powder, the porous carbide may be pulverized so as to have approximately the same particle size as the iron powder.

When mixing or kneading, water is added to the porous carbide, binder, and iron as required. By adding water, the generation of dust can be prevented, and the porous carbide and the iron powder can be more uniformly mixed.

A kneader can be used for mixing and kneading these raw materials. As the kneader, for example, a single-screw kneader, a twin-screw kneader, a mixing roll, a kneader, or a Banbury mixer can be used. Alternatively, a kneader having both mixing and kneading functions may be used. In this case, the porous carbide, iron powder, and binder are put into a kneader and then mixed and kneaded. Alternatively, mixing and kneading may be performed continuously. For example, the porous carbide and iron powder are put into a kneader and mixed, and then the binder is put into the kneader and kneaded. The binder may be added all at once, intermittently, or continuously. By adding a binder and kneading after mixing the porous carbide and the iron powder, aggregation of the porous carbide and the iron powder can be prevented and foaming can be suppressed.

The kneading temperature can be arbitrarily set, and may be, for example, 0° C. or higher and 50° C. or lower, or 10° C. or higher and 40° C. or lower. The kneading time may also be appropriately set in consideration of the mixing ratio and amount of raw materials, the type of binder, the capacity of the kneader, etc. For example, 1 second or more and 1 hour or less, 1 minute or more and 30 minutes or less, or 1 minute or more and 15 minutes. It can be set from the following range.

Through the steps described above, a pasty mixture of the porous carbide, the binder, and the iron powder can be obtained as the core 102 . In this step, part of the iron powder may be oxidized, and as a result, the mixture contains compounds containing bivalent and/or trivalent iron (Fe(II), Fe(III)). Examples of iron compounds include iron hydroxide and iron oxide, as described above. Also, during mixing and kneading, an alkali metal and/or alkaline earth metal compound may be added.

2-2. Granulation As an optional step, the mixture may be granulated and formed into a shape such as pellets. Molding of the mixture can be carried out using a granulator. Examples of granulators include compression granulators, extrusion granulators, roll granulators, blade granulators, melt granulators, and spray granulators.

When an extrusion type granulator is used, a pasty mixture formed into a predetermined shape is extruded from a die attached to the granulator. The extruded mixture is cut into a predetermined length and formed into pellets whose extrusion direction is the height direction. The length of the mixture (length L of the pellet) can be adjusted by adjusting the extrusion speed and cutting speed of the mixture in the extrusion granulator (the rotation speed of the cutter in the case of a rotary cutting method). Further, by adjusting the opening diameter of the die, the diameter of the mixture (diameter D when the end face shape is circular) can be adjusted. Therefore, by using an extrusion granulator, it is possible to obtain a pellet-shaped (for example, substantially cylindrical) mixture with a controlled size. The size of the pellet is adjusted, for example, to have a diameter D and a length L within the ranges described above.

Through the steps described above, the core 102 is formed.

2-3. Formation of Coating Layer Next, the coating layer 104 is formed on the surface of the core 102 . Specifically, the liquid raw material for the coating layer 104 described above is applied to the surface of the core 102 by spray coating or dip coating. After that, the solvent contained in the raw material may be distilled off. In the case of spray coating, for example, the raw material may be sprayed while rotating the core 102 on a pan-type granulator. The thickness of the coating layer 104 can be appropriately adjusted depending on the concentration of the raw material, the number of times of application, and the like.

When the raw material of the coating layer 104 is solid, for example, the molded pellet-like core 102 is put into a pan-type granulator, and water or alcohol is sprayed while rotating the core 102 . After that, the raw material is introduced to adhere the raw material of the coating layer 104 to the surface of the core 102 . After that, the coating layer 104 is formed by distilling off the water and alcohol used for bonding the core 102 and the raw material.

The adsorbent 100 is produced by the above steps.

2-4. Carbon Dioxide Treatment Optionally, carbon dioxide treatment may be performed. Specifically, the material is treated with a gas containing carbon dioxide during mixing and kneading of raw materials, after molding, or after forming a coating layer. This treatment may be performed, for example, by introducing a carbon dioxide-containing gas into the kneader during mixing and kneading of the raw materials, or by introducing a carbon dioxide-containing gas into the adsorbent 100 after molding or after forming the coating layer. may be brought into contact. As the gas, a carbon dioxide concentration or a mixed gas containing carbon dioxide and other gases is used. Other gases include nitrogen, oxygen, air, noble gases such as argon, and water (water vapor). The carbon dioxide concentration in the gas can also be arbitrarily set, for example, it can be set appropriately from the range of 1% to 100% by volume, 1% to 50% by volume, or 1% to 20% by volume. The temperature in this treatment can be, for example, 0° C. or higher and 80° C. or lower, or 0° C. or higher and 50° C. or lower, and is typically room temperature (25° C. or thereabouts). By this treatment, all or part of the alkali metal or alkaline earth metal compounds contained in the porous carbide or added during the above-described mixing and kneading are converted into carbonates or hydrogencarbonates.

An example of the supply source of the gas containing carbon dioxide is a gas cylinder or tank containing carbon dioxide. Alternatively, exhaust gas from facilities that emit a large amount of carbon dioxide (chemical plants, waste incineration facilities, thermal power plants, other various factories, etc.), or obtained by performing dust removal, desulfurization, denitrification, etc. on exhaust gas Purified carbon dioxide may be utilized. When facilities that emit a large amount of carbon dioxide are close to the manufacturing site of the adsorbent 100, these facilities function as a supply source of gas containing carbon dioxide, so the cost for transporting carbon dioxide is reduced, and transportation is easier. Secondary emissions of accompanying carbon dioxide are prevented.

2-5. drying (curing)
Furthermore, as an optional step, the mixture after molding or the adsorbent 100 after forming the coating layer 104 may be dried. The drying temperature and time are also appropriately selected depending on the amount of mixture or adsorbent 100 and the amount of water involved. For example, the drying temperature may be selected from the range of 30°C to 400°C, 50°C to 300°C, and 100°C to 300°C. The humidity during drying may be 20% or more and 95% or less, or 50% or more and 90% or less. The drying time is also appropriately selected from the range of 1 minute to 1 week, 1 hour to 3 days, or 3 hours to 1 day. The atmosphere during drying may be, for example, air, nitrogen, a rare gas such as argon, or a mixture thereof. In addition, the carbon dioxide treatment described above may serve as the drying step. That is, the amount of water contained in the core 102 may be reduced by treating it with a gas containing carbon dioxide.

It should be noted that, in manufacturing the adsorbent 100 according to one embodiment of the present invention, calcination at a high temperature may not be performed. That is, it is not necessary to heat the binder at a temperature (for example, 400° C. or higher) necessary for carbonizing the binder. Therefore, the time and energy required for calcination are not required, and the adsorbent 100 can be provided at a lower cost.

As described above, in the method of manufacturing the adsorbent 100 according to one embodiment of the present invention, the core 102 comprising porous carbide, binder and iron is covered with the coating layer 104 . Therefore, the physical strength is improved by the coating layer 104, and the collapse of the adsorbent 100 in water can be prevented. Furthermore, the ignitability of the combustible porous charcoal is greatly reduced, so the adsorbent 100 can be handled as a highly safe non-dangerous material. Further, as shown in Examples, the adsorbent 100 exhibits a sufficient ability to adsorb phosphoric acid even when the coating layer 104 is formed. Therefore, it can be said that the adsorbent 100 according to one embodiment of the present invention is an adsorbent having both high phosphoric acid adsorption capacity and safety.

<Second embodiment>
In this embodiment, a system that contributes to the reduction of carbon dioxide in the atmosphere via the adsorbent 100 described in the first embodiment will be described with reference to FIG.

As described in the first embodiment, porous charcoal obtained from biomass can be used as one of raw materials in manufacturing the adsorbent 100 according to one embodiment of the present invention. At this time, by using dry distillation gas obtained by carbonization of biomass as combustible gas, power generation and hot water production can be performed (Fig. 3, (1)). This means that the energy and by-products generated during the production of the present adsorbent 100 are effectively utilized.

The obtained porous carbide is mixed and kneaded with iron powder and a binder to give the core 102 of the adsorbent 100, and the core 102 is further coated with the coating layer 104 to obtain the adsorbent 100 (FIG. 3, (2) ). Carbide on which iron or iron compounds are supported effectively adsorbs contaminants in water, especially phosphorus-containing compounds such as phosphoric acid. Therefore, water quality can be improved by installing this adsorbent 100 in a water area such as a river, a lake, or the sea (FIG. 3, (3)).

Phosphoric acid adsorbed by the adsorbent 100 is a typical nutrient component that promotes the growth of various plants. Therefore, the adsorbent 100 that adsorbs phosphoric acid can be used as a fertilizer. For example, the adsorbent 100 subjected to the water quality improvement treatment is sprayed on the farmland as it is or after being crushed and classified (FIG. 3, (4)). Alternatively, it may be applied after mixing with fertilizer aids such as calcium sulfate and other fertilizer components. Fertilizer components to be added include one or more selected from nitrogen, potassium, calcium, magnesium, manganese, silicic acid, and boron. Bat guano, pokashi manure, plant ash, lime, chemical fertilizers and the like are exemplified.

The dispersed adsorbent 100 slowly releases the adsorbed phosphoric acid, and the phosphoric acid is utilized for plant growth. At this time, plants use carbon dioxide in the atmosphere as a carbon source for photosynthesis and grow (Fig. 3, (5)). Plants are then used in various ways, such as foodstuffs and materials. The plant after utilization can be reused as biomass for the production of porous charcoal (Fig. 2, (6)).

In this way, by applying the embodiment of the present invention, a series of processes including generation of porous carbon from biomass, manufacture of adsorbent 100, improvement of water quality and manufacture of fertilizer, growth of plants using fertilizer, and regeneration of biomass can be achieved. A cycle is established. In this cycle, atmospheric carbon dioxide fixed by plants is used as a carrier for iron and iron compounds that exhibit phosphate adsorption function, and is stored underground in the form of carbon. Therefore, this cycle is a system for reducing and storing carbon dioxide in the atmosphere into the ground, and contributes to the reduction of carbon dioxide in the atmosphere.

In this example, production of the adsorbent 100 according to one embodiment of the present invention and evaluation results of the adsorbent 100 will be described.

1. Preparation of adsorbent 1-1. Example 1
Irregular shaped charcoal (woody biomass gasification power generation waste coal) was used as the raw material porous charcoal. In this 45 g of charcoal, the ratio of iron particles having a particle size in the range of 300 μm to 600 μm is 24% by mass, the ratio of iron particles having a particle size in the range of 75 to 300 μm is 56% by mass, and the ratio is 1 μm to less than 75 μm. Iron powder containing 20% by mass of iron particles having a particle size in the range of was added and mixed for 1 minute with a spatula. At room temperature, 7 g of molasses (solid content: 70%), calcined gypsum and 40 mL of water were added and mixed to obtain a powder mixture.

Next, the obtained powder mixture was charged into a granulator and formed into pellets having a diameter of 6 mm and a height of 9 mm to obtain cores 102 .

After that, the obtained core 102 is put into a pan-type granulator, and while rotating the core 102, an aqueous solution obtained by diluting 200% of the weight of sodium silicate No. 3 with water to 75% is applied to the core 102. was sprayed. After that, the adsorbent 100 was obtained by drying (curing) in the air at 20° C. for 24 hours.

1-2. Examples 2 to 4
Adsorbents 100 of Examples 2 to 4 were produced in the same manner as in Example 1 by changing the type of binder, the material of the coating layer 104, the drying temperature and time, and the like. Detailed conditions are as shown in Table 1. In Examples 2 and 3, carbon dioxide was used in place of argon, and carbonation was performed by drying (curing) at a humidity of 80%.

1-3. Comparative Example As a comparative example, an adsorbent was produced in the same manner as in Example 1. However, the coating layer 104 was not formed.

2. Evaluation 2-1. Phosphorus Adsorbing Capacity and Shape Stability Using a batch method, the adsorption amount of phosphoric acid of the adsorbent 100 of Example was evaluated. 0.1 g of any one of the adsorbents of Examples 1 to 4 was added to 50 mL of a 200 mg/L phosphoric acid solution, shaken horizontally at 23° C. and 100 rpm until an equilibrium concentration was reached, and then filtered. The phosphorus concentration of the filtrate was determined by molybdenum blue spectrophotometry. Table 1 shows the results. As shown in Table 1, it was confirmed that the adsorbents 100 of any of the examples exhibited the ability to adsorb phosphoric acid.

In addition, it was confirmed that the adsorbent maintained almost its initial shape in the phosphoric acid solution after the phosphoric acid adsorption capacity evaluation in all the examples. On the other hand, the adsorbent of the comparative example collapsed in water. From this, it is understood that the adsorbent 100 having the core 102/coating layer 104 structure is less susceptible to water erosion and exhibits high shape stability in water.
2-2. Small Gas Flame Ignition Test The adsorbents obtained in Examples 1 to 4 were subjected to a small gas flame ignitability test. Specifically, 1.5 g of the adsorbent was placed on a porcelain heat-resistant plate, and ignition was attempted using a gas burner. The flame length of the gas burner was about 70 mm, the contact area between the flame and the adsorbent was 1 to 2 cm ₂ , the contact between the flame and the adsorbent was about 30°, and the contact time between the flame and the adsorbent was 10 seconds. This operation was repeated 10 times. As a result, it was confirmed that none of the adsorbents ignited.

These results indicate that the adsorbent 100 having the coating layer 104 has both shape stability in water and non-ignitability without impairing the ability to adsorb phosphoric acid. Therefore, by applying one of the embodiments of the present invention, it is possible to provide an adsorbent that is highly effective in improving water quality over a long period of time and that can be safely handled as a non-dangerous material.

Each of the embodiments described above as embodiments of the present invention can be implemented in combination as appropriate as long as they do not contradict each other. Appropriate additions, deletions, or design changes made by those skilled in the art based on each embodiment are also included in the scope of the present invention as long as they have the gist of the present invention.

Even if there are other actions and effects different from the actions and effects brought about by each of the above-described embodiments, those that are obvious from the description of the present specification or those that can be easily predicted by those skilled in the art are, of course, the present invention. is understood to be brought about by

100: adsorbent, 102: core, 104: coating layer

Claims (16)

An adsorbent having a core comprising porous carbide, a binder, and iron powder, and a coating layer covering at least a portion of said core. The adsorbent according to claim 1, wherein the adsorbent has a pellet shape with a length to diameter of 0.5 or more and 5 or less and a diameter of 1 mm or more and 20 mm or less. 2. Adsorbent according to claim 1, wherein the coating layer comprises a material selected from sodium silicate, potassium silicate, silicon oxide, resin, iron powder, gypsum, cement. said core further comprising a compound of a metal selected from alkali metals and alkaline earth metals;
2. The adsorbent of claim 1, wherein said compound is selected from chlorides, oxides, hydroxides, sulfates, nitrates, carbonates and bicarbonates of said metal. The content of the porous carbide is 20% by mass or more and 80% by mass or less,
The content of the binder is 5% by mass or more and 50% by mass or less,
The content of the iron powder is 5% by mass or more and 35% by mass or less.
The adsorbent according to claim 4, wherein the metal content is 1% by mass or more and 10% by mass or less. The carbon content is 10% by mass or more and 80% by mass or less,
The iron content is 5% by mass or more and 35% by mass or less,
The adsorbent according to claim 4, wherein the metal content is 1% by mass or more and 30% by mass or less. 2. The adsorbent of claim 1, further comprising an iron compound. 8. Adsorbent according to claim 7, wherein the iron compound is selected from divalent and trivalent iron oxides and divalent and trivalent iron hydroxides. The binder includes molasses, blackstrap molasses, starch, dextrin, cornstarch, rice bran, polyvinyl alcohol, a copolymer of vinyl acetate and ethylene or a saponified product thereof, pulp waste liquid, ligninsulfonate, carboxymethylcellulose, hydroxypropylmethylcellulose, alginic acid. 2. The adsorbent of claim 1 selected from sodium, phenolic resins, tarpitch gypsum, cement, ground granulated blast furnace slag, fly ash, gypsum of Paris, and sodium silicate. A method of making an adsorbent, comprising mixing a porous carbide with a binder and iron powder to form a mixture; and forming a coating layer over at least a portion of the mixture. 11. The manufacturing method according to claim 10, further comprising molding the mixture into a pellet shape having a length to diameter of 0.5 or more and 5 or less and a diameter of 1 mm or more and 20 mm or less. 11. The manufacturing method according to claim 10, wherein the coating layer comprises a material selected from sodium silicate, potassium silicate, silicon oxide, resin, iron powder, gypsum and cement. 11. The method of claim 10, further comprising treating said mixture with a gas comprising carbon dioxide. 11. The manufacturing method of claim 10, further comprising drying said mixture. 11. The manufacturing method according to claim 10, wherein water is further added when mixing the porous carbide with the binder and the iron powder. The binder includes molasses, blackstrap molasses, starch, dextrin, cornstarch, rice bran, polyvinyl alcohol, a copolymer of vinyl acetate and ethylene or a saponified product thereof, pulp waste liquid, ligninsulfonate, carboxymethylcellulose, hydroxypropylmethylcellulose, alginic acid. 11. The manufacturing method according to claim 10, selected from sodium, phenolic resin, tarpitch gypsum, cement, ground granulated blast furnace slag, fly ash, calcined gypsum, and sodium silicate.

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