Adsorbent

Abstract

To provide an adsorbent having excellent adsorption properties, with reduced elution of iron.SOLUTION: An adsorbent includes a porous carbide and iron. The organic carbon content in the carbide is 30% or more and 85% or less. The adsorbent includes a porous carbide and iron, and has a specific surface area of 100 m2 / g or more and 500 m2 / g or less. The adsorbent includes a porous carbide and iron, and has a total pore volume of 1000 mm3 / g or more and 3000 mm3 / g or less. The adsorbent includes a porous carbide and iron, and has an iron content of 5% or more and 35% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to an adsorbent. In particular, this invention relates to an adsorbent that adsorbs phosphorus. [Background technology]

[0002] To reduce the amount of carbon dioxide in the atmosphere, technologies are known to artificially capture carbon dioxide and store it underground. For example, biomass such as wood and agricultural products can be used to absorb carbon dioxide from the atmosphere and fix it as organic carbon. However, since this biomass is organic matter, if it is stored underground as is, it will only rot and decompose, releasing carbon dioxide back into the atmosphere. On the other hand, when biomass is heated in an oxygen-free environment, oxygen and hydrogen atoms are removed, producing carbonized material consisting of carbon and ash. This carbonized material is a mass of carbon that does not contain sugar chains or amino acids that are decomposed by microorganisms, so it is very stable in the environment (underground) and hardly decomposes. Carbonized biomass has been used in agriculture for a long time and is recognized as a soil conditioner under the Soil Fertility Improvement Law, so by applying it to farmland, carbon dioxide can be sequestered and stored underground. In other words, using carbonized biomass in agriculture contributes to reducing the amount of carbon dioxide in the atmosphere. However, considering the costs involved in manufacturing carbonized materials and current carbon pricing, simply using carbonized materials for soil improvement is not cost-effective.

[0003] On the other hand, carbides are known to have a very large surface area because they are porous. Taking advantage of this large surface area, carbides are used as adsorbents for a variety of substances. For example, Patent Document 1 describes a phosphorus recovery material using calcium-supported carbides. By adsorbing phosphorus using such a phosphorus recovery material, water pollution caused by phosphorus discharge into natural water bodies can be suppressed. Furthermore, when phosphorus recovery material with adsorbed phosphorus is buried in farmland, the phosphorus adsorbed on the material is dissolved by organic acids released from the roots of crops. This phosphorus functions as fertilizer for crops, thus improving yields in farmland where the phosphorus recovery material is buried, or enabling the growth of high-quality crops.

[0004] Thus, the demand for carbonized materials is increasing not only for improving soil quality, but also for their ability to suppress environmental pollution by adsorbing certain substances, or for their ability to apply those harmful substances to other uses. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2007-75706 [Patent Document 2] Japanese Patent Publication No. 2020-11211 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the phosphorus recovery material described in Patent Document 1 requires the use of a material rich in silicon, such as rice husks or diatomaceous earth. When using a material rich in silicon, there is a limit to the amount of phosphorus recovery material that can be produced. Furthermore, there is a limit to the amount of phosphorus and other substances that can be adsorbed.

[0007] Furthermore, Patent Document 2 describes an adsorbent made of iron-containing carbide. Carbide has high conductivity, and electron exchange occurs rapidly between it and the iron attached to the pores in the carbide. Therefore, when an adsorbent made of iron-containing carbide is placed in water, the iron ionizes, producing hydroxides such as iron oxyhydroxide (FeOOH), which react with phosphate ions present in the water to form iron phosphate, which can then be adsorbed and fixed onto the carbide. In other words, an adsorbent made of iron-containing carbide can efficiently adsorb phosphorus through the above mechanism.

[0008] On the other hand, if iron leaches out from the adsorbent, it will release the adsorbed phosphorus, so there was a need to reduce the leaching of iron from the adsorbent.

[0009] One embodiment of the present invention has been made in view of the above-mentioned problems, and one of its objectives is to provide an adsorbent that has excellent adsorption properties and reduced iron elution. [Means for solving the problem]

[0010] An adsorbent according to one embodiment of the present invention consists of an iron-containing carbide, wherein the organic carbon content in the carbide is 30% to 85%.

[0011] An adsorbent according to one embodiment of the present invention comprises porous carbide and iron, and has a specific surface area of ​​100 m². 2 / g or more 500m 2 It is less than / g.

[0012] An adsorbent according to one embodiment of the present invention comprises porous carbide and iron, and has a total pore volume of 1000 mm². 3 / g or more 3000mm 3 It is less than / g.

[0013] The iron content may be between 5% and 35%.

[0014] The organic carbon content in the carbide may be between 50% and 85%.

[0015] At least a part of the organic carbon may be produced by firing at least one selected from molasses, waste molasses, starch, dextrin, corn starch, rice bran, polyvinyl alcohol, pulp waste liquor, lignin sulfonate, carboxymethyl cellulose, hydroxypropyl methyl cellulose, sodium alginate, phenol resin, and tar pitch.

[0016] The adsorbent may be a substantially cylindrical pellet. <000,0094> The adsorbent may have a phosphorus adsorption amount of 5 mg-P / g or more.

Advantages of the Invention

[0018] <,ooo,100>The adsorbent according to one embodiment of the present invention has reduced elution of iron and excellent adsorption characteristics. In addition, since the adsorbent can be manufactured without the need for a special manufacturing apparatus, the manufacturing cost of the adsorbent can be suppressed, and an inexpensive adsorbent can be provided.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic diagram of the adsorbent according to one embodiment of the present invention. [Figure 2] It is a flowchart showing a method for manufacturing the adsorbent according to one embodiment of the present invention. [Figure 3] It is a diagram for explaining a method for manufacturing the adsorbent according to one embodiment of the present invention.

Modes for Carrying Out the Invention

[0020] <00001,6>Hereinafter, an adsorbent and a method for manufacturing the adsorbent according to one embodiment of the present invention will be described with reference to the drawings. However, the adsorbent and the method for manufacturing the adsorbent according to one embodiment of the present invention can be carried out in many different forms and should not be interpreted as being limited to the examples shown below. In the drawings referenced in this embodiment, the same part or part having a similar function will be given the same reference numeral or the same reference numeral followed by an alphabet letter, and repeated descriptions will be omitted.

[0021] [1. Composition of the adsorbent 10] The configuration of the adsorbent 10 will be described with reference to Figure 1.

[0022] Figure 1 is a schematic diagram of an adsorbent 10 according to one embodiment of the present invention. As shown in Figure 1, the adsorbent 10 includes a first carbide 100, iron 110, and a second carbide 120. In the adsorbent 10, the first carbide 100 and the second carbide 120 may be the same carbide or may be different carbides. As will be described in detail later, the first carbide 100 and the second carbide 120 have different raw materials. Therefore, for convenience, the first carbide 100 and the second carbide 120 will be distinguished and described below based on the difference in raw materials.

[0023] The adsorbent 10 is a so-called pellet. As will be described in detail later, the adsorbent 10 is granulated and formed into pellets. The shape of the adsorbent 10 is, for example, roughly cylindrical, roughly elliptical, or roughly polygonal, but is not limited to these.

[0024] The approximate cylindrical shape is preferably a perfect cylinder, but is not limited to this. The ratio of the major axis to the minor axis (major axis / minor axis) of the approximate cylindrical shape is between 1 and 5. On the other hand, if the ratio of the major axis to the minor axis (major axis / minor axis) is greater than 5, it is considered an approximate elliptical cylinder. Furthermore, the opposite faces of the approximate cylindrical shape do not have to be the same size. Note that the approximate cylindrical shape in this specification also includes approximate cylindrical shapes with a portion missing.

[0025] A roughly polygonal prism shape includes, for example, a triangular prism, a quadrangular prism, a pentagonal prism, or a hexagonal prism. Opposite faces of a roughly polygonal prism do not have to be the same size. In this specification, a roughly polygonal prism shape also includes a roughly polygonal prism shape that is partially missing.

[0026] The shape of the adsorbent 10 is generally determined by the shape of the granules 20, which will be described later. The height H of the adsorbent 10 (see Figure 1) is 1 mm or more and 20 mm or less, preferably 3 mm or more and 15 mm or less, and more preferably 6 mm or more and 12 mm or less. The major axis D of the adsorbent 10 (maximum diameter perpendicular to the height, see Figure 1) is 1 mm or more and 20 mm or less, preferably 2 mm or more and 10 mm or less, and more preferably 3 mm or more and 8 mm or less. The size of the adsorbent 10 can be controlled during the manufacturing process of the adsorbent 10. Therefore, it is preferable that the size of the adsorbent 10 be within the above range, which is easy to use and has a high adsorption effect.

[0027] The adsorbent 10 may be porous. That is, the first carbide 100 and the second carbide 120 may be porous. In the adsorbent 10, iron 110 may be contained within the porous structure of the first carbide 100 and the second carbide 120.

[0028] [2. Method for manufacturing the adsorbent 10] A method for manufacturing the adsorbent 10 according to one embodiment of the present invention will be described with reference to Figures 2 and 3.

[0029] Figure 2 is a flowchart illustrating a method for manufacturing the adsorbent 10 according to one embodiment of the present invention. Figure 3 is a diagram illustrating a method for manufacturing the adsorbent 10 according to one embodiment of the present invention.

[0030] As shown in Figure 2, the method for manufacturing the adsorbent 10 includes a mixing step (S110), a kneading step (S120), a granulation step (S130), and a calcination step (S140). Each step will be described below.

[0031] [2-1. Mixing process (S110)] In the mixing step (S110), as shown in FIG. 3(A), the carbide 200 and the iron compound 210 are mixed.

[0032] The carbide 200 is, for example, charcoal, bamboo charcoal, white charcoal, black charcoal, sawdust charcoal, coconut shell charcoal, rice husk charcoal, or pulverized coal. The carbide 200 can be produced by carbonizing organic substances such as standing trees (including thinned wood of broad-leaved trees, coniferous trees, bamboo, etc., and forest waste materials), waste materials from sawmills or wood processing factories (including sawdust, bark chips, chip waste, and end cuts), plant shells, building demolition materials, or wooden waste materials of furniture.

[0033] Carbonization of the organic substance is carried out by heating the organic substance under 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 carbonizing the organic substance under a reduced-pressure atmosphere, it can be carried out under 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, a high-vacuum state of 10 -5 Pa or more and 10 -1 Pa or less, or an ultra-high-vacuum state of 10 -5 Pa or less. Also, when carbonizing the organic substance under a low-oxygen atmosphere, the oxygen concentration can be 0.01% or more and 3% or less, preferably 0.1% or more and 2% or less. The heating temperature in the carbonization of the organic substance is 400°C or more and 1200°C or less, preferably 500°C or more and 1100°C or less, more preferably 600°C or more and 1000°C or less, and particularly preferably 600°C or more and 900°C or less. Also, the heating time is 10 minutes or more and 10 days or less, preferably 10 minutes or more and 5 hours or less.

[0034] The carbonization of organic matter can be carried out using internal combustion or external heating methods, employing batch-type open or closed carbonization furnaces, continuous-type rotary kilns or oscillating carbonization furnaces, screw furnaces, heating chambers, or covered heat-resistant containers (crucibles). An internal heating method is a carbonization furnace that obtains the heat necessary for carbonization from the material itself, and can carbonize organic matter by supplying the oxygen necessary for combustion. An external heating method is a carbonization furnace that supplies the heat necessary for carbonization from the outside, and can carbonize organic matter by blocking oxygen.

[0035] When organic matter is heated under reducing conditions, the composition of the organic matter begins to decompose during the heating process (for example, at approximately 280°C). Oxygen or hydrogen within the organic matter volatilizes as gases such as carbon dioxide, carbon monoxide, hydrogen, or hydrocarbons, and the organic matter transforms into amorphous carbon with a high carbon content. Further heating at higher temperatures reduces the oxygen or hydrogen within the organic matter even more, producing carbide 200 composed of highly pure fixed carbon and ash. As water or constituent components within the organic matter are released as volatile gases, the carbide 200 produced by the carbonization of organic matter becomes porous, with numerous continuous pores of various sizes. Furthermore, as carbonization progresses with increasing heating temperature, the carbide 200 produced acquires heat-resistant (fire-resistant), adsorbent, or conductive properties. Therefore, the carbide 200 may be porous and may possess heat-resistant (fire-resistant), adsorbent, or conductive properties.

[0036] The iron compound 210 may be a divalent iron compound, a trivalent iron compound, or a mixture of divalent and trivalent iron. Examples of iron compound 210 include iron oxide, iron chloride, iron nitrate, iron sulfate, iron acetate, or iron oxalate. Among these, iron oxide is preferred as iron compound 210 because it is stable and inexpensive. Examples of iron oxide include FeO (wustite), Fe2O3 (hematite or maghemite), or Fe3O4 (magnetite). The iron compound 210 may be a single compound or may contain multiple compounds.

[0037] Furthermore, a metal compound other than iron can be used instead of iron compound 210. Examples of metals other than iron include aluminum, vanadium, nickel, cobalt, manganese, magnesium, calcium, or alloys thereof.

[0038] Carbide 200 often contains water, and the water content varies depending on the type of carbide 200. Therefore, when calculating the mixing ratio of carbide 200 and iron compound 210, the amount of solid components of carbide 200 is used as the basis. For example, if 100g of carbide 200 contains 5% water, the amount of solid components of carbide 200 can be calculated as 100 × 0.95 = 95 (g).

[0039] The mixing ratio of the amount of solid component (α) of the carbide 200 to the amount of iron compound (β) is α:β = 100:1 to 80, preferably α:β = 100:10 to 50, and more preferably α:β = 100:20 to 40. When the mixing ratio is within the above range, the carbide 200 and iron compound 210 are uniformly mixed without aggregation.

[0040] When mixing the carbide 200 and the iron compound 210, the particle sizes of the carbide 200 and the iron compound 210 may be adjusted. By adjusting the particle sizes of the carbide 200 and the iron compound 210, the carbide 200 and the iron compound 210 can be mixed uniformly. The particle sizes of the carbide 200 and the iron compound 210 can be adjusted by crushing either the carbide 200 or the iron compound 210. In particular, since the particle size of the carbide 200 is often larger than that of the iron compound 210, the carbide 200 may be crushed to match the particle size of the carbide 200 to that of the iron compound 210.

[0041] Although the carbide 200 and iron compound 210 can also be crushed in the kneading process (S120) described later, fine adjustment of particle size is difficult in the kneading process (S120). Therefore, when adjusting the particle size of the carbide 200 and iron compound 210, it is preferable to adjust the particle size of each of the carbide 200 and iron compound 210 in advance in the mixing process (S110).

[0042] The size of the carbide 200 and iron compound 210 is not particularly limited, but preferably the average particle diameter of the carbide 200 is 1 μm or more and 50 mm or less, and the average particle diameter of the iron oxide is 1 μm or more and 10 mm or less, preferably the average particle diameter of the carbide 200 is 5 μm or more and 2 mm or less, and the average particle diameter of the iron oxide is 1 μm or more and 1 mm or less. When the sizes of the carbide 200 and iron compound 210 are within the above range, not only are the carbide 200 and iron compound 210 uniformly mixed, but in the kneading step described later, the organic binder 220 can adhere to the surface of each of the carbide 200 and iron compound 210, allowing them to be integrated.

[0043] In mixing the carbide 200 and the iron compound 210, a certain amount of water may be added. Adding water prevents the generation of dust in the mixing step (S110) and allows the carbide 200 and the iron compound 210 to be uniformly kneaded in the kneading step (S120) described later.

[0044] The above mixing step (S110) produces a mixture of carbide 200 and iron compound 210.

[0045] [2-2. Mixing Process (S120)] In the kneading step (S120), as shown in Figure 3(B), an organic binder 220 is added to the mixture (carbide 200 and iron compound 210) and kneaded to produce a paste.

[0046] As the organic binder 220, for example, molasses, waste molasses, starch, dextrin, corn starch, rice bran, polyvinyl alcohol, pulp waste liquid, lignin sulfonate, carboxymethylcellulose, hydroxypropylmethylcellulose, sodium alginate, phenolic resin, or tar pitch can be used. The organic binder 220 may contain one type of material or multiple types of materials. In particular, molasses or waste molasses is preferred as the organic binder 220. Molasses has a high solid component content, making it easy to solidify the paste. Also, because molasses has a high carbon content, it can efficiently reduce the granulated material in the calcination process (S140) described later. Furthermore, because molasses is inexpensive and contains few harmful components, the manufacturing cost of the adsorbent can be suppressed, and the manufactured adsorbent can be used as a safe fertilizer.

[0047] The viscosity of the organic binder 220 can be adjusted as needed. For example, the viscosity of the organic binder 220 can be adjusted by adding water or an organic solvent. If the viscosity of the organic binder 220 is too high, it will be difficult to knead. Also, if the viscosity of the organic binder 220 is too low, the viscosity of the paste must be adjusted before the granulation step (S130) described later. Adjusting the viscosity of the paste is done by evaporating the added water or organic solvent, but this not only requires the step of evaporating the water or organic solvent, but the evaporation of water or organic solvent causes aggregation of the carbide 200 and iron compound 210, reducing the dispersibility of the carbide 200 and iron compound 210 in the organic binder 220. For this reason, it is preferable that the viscosity of the organic binder 220 be adjusted before kneading with the mixture.

[0048] The amount of organic binder 220 added is also based on the amount of solid components of carbide 200. The ratio of the amount of solid components of carbide 200 (α) to the amount of solid components of organic binder 220 (γ) is α:γ = 100:10 to 1000, preferably α:γ = 100:100 to 500, and more preferably α:γ = 100:100 to 300.

[0049] In the mixing process (S120), the parameters that determine the dispersibility of the carbide 200 and iron compound 210 in the organic binder 220 are not limited to the mixing ratio of the mixture to the organic binder 220. The dispersibility in the mixing process (S110) can also be controlled by parameters such as the mixing temperature or mixing time of the kneader. Therefore, the kneader will be described below.

[0050] A kneader can be used for mixing the mixture with the organic binder 220. Examples of kneaders include single-screw kneaders, twin-screw kneaders, mixing rolls, kneaders, or Banbury mixers.

[0051] A kneader with a mixing function may also be used. In that case, the mixing process (S110) and the kneading process (S120) can be carried out continuously. For example, the carbide 200 and the iron compound 210 are put into the kneader and mixed. Subsequently, the organic binder 220 is put into the kneader and kneaded with the mixture. The carbide 200, the iron compound 210, and the organic binder 220 can also be put into the kneader all at once and mixed and kneaded, but the carbide 200 and the iron compound 210 tend to agglomerate and bubbles tend to be generated. For this reason, it is preferable to carry out the mixing process (S110) and the kneading process (S120) separately. Furthermore, by using a kneader in the kneading process (S120), a constant amount of the organic binder 220 can be added to the mixture at a constant speed.

[0052] Furthermore, the mixing temperature can be set arbitrarily, but is between 0°C and 50°C, preferably between 10°C and 40°C. The mixing time is preferably between 1 second and 1 hour, preferably between 1 minute and 30 minutes, and more preferably between 1 minute and 15 minutes. By setting the parameters of the mixing step (S120) within the above range, the dispersibility of the carbide 200 and iron compound 210 in the organic binder 220 can be optimized.

[0053] Through the above mixing process (S120), a paste is produced in which the carbide 200 and the iron compound 210 are dispersed in the organic binder 220.

[0054] [2-3. Granulation process (S130)] In the granulation process (S130), as shown in Figure 3(C), the paste is granulated to produce granules 20 containing carbide 200, iron compound 210, and organic binder 220.

[0055] The granules 20 can be produced using a granulator. Examples of granulators include compression granulators, extrusion granulators, roll granulators, blade granulators, melt granulators, and spray granulators. For the production of approximately cylindrical granules 20, an extrusion granulator is preferable. Here, the production of granules 20 using an extrusion granulator will be described.

[0056] An extrusion-type granulator extrudes paste formed into a predetermined shape from a fitted die. The extruded paste is cut to a predetermined length, producing pellet-shaped granules 20 with the extrusion direction being the height direction. The length of the granules 20 (height of the pellet shape) can be adjusted by adjusting the cutting speed of the extrusion-type granulator (or the rotation speed if it is a rotary cutting method). In addition, the diameter of the granules 20 (or diameter if the cross-sectional shape is circular) can be adjusted by adjusting the opening diameter of the die. Therefore, by using an extrusion-type granulator, it is possible to produce granules 20 having a pellet shape with controlled size (for example, approximately cylindrical).

[0057] The length of the granules 20 is 1 mm or more and 20 mm or less, preferably 3 mm or more and 15 mm or less, and more preferably 6 mm or more and 12 mm or less. The diameter of the granules 20 is 1 mm or more and 20 mm or less, preferably 2 mm or more and 10 mm or less, and more preferably 3 mm or more and 8 mm or less. When the size of the granules 20 is within the above range, the iron compound 210 can be sufficiently reduced in the calcination process (S140) described later, thereby enhancing the adsorption effect of the adsorbent 10.

[0058] The cross-sectional shape of the granules 20 is not limited to a circle. The cross-sectional shape of the granules can also be changed by changing the opening shape of the die. The cross-sectional shape of the granules may be, for example, elliptical or polygonal. In other words, the granules 20 may be in the shape of an elliptical or polygonal prism pellet, not just a cylinder.

[0059] In the granulation process (S130), an auxiliary agent may be added to stabilize the pellet shape of the granulated material 20. Examples of auxiliary agents include organic resins such as polyester resin, acrylic resin, phenolic resin, epoxy resin, silicone resin, polyimide resin, polystyrene resin, or urethane resin. In the firing process (S140) described later, these organic resins are carbonized, and the resulting carbonized material can also function as an adsorbent.

[0060] The above granulation process (S130) produces granules 20 containing carbide 200, iron compound 210, and organic binder 220.

[0061] [2-4. Firing Process (S140)] In the firing process (S140), the granulated material 20 is fired to produce the adsorbent material 10.

[0062] The granules 20 are calcined by heating them under a reducing atmosphere. The granules 20 contain an organic binder 220. When the organic binder 220 is heated, reducing gases such as carbon monoxide, hydrogen, hydrogen sulfide, sulfur dioxide, or hydrocarbon gases are generated. Therefore, a reducing atmosphere can be formed using the reducing gas generated from the granules 20 without introducing a separate reducing gas. In other words, the iron compound 210 can be reduced using the reducing gas generated from the granules 20. Moreover, since reducing gas can be generated inside the granules 20, the iron compound 210 inside the granules 20 can be sufficiently reduced. Furthermore, the iron compound 210 is reduced to iron 110 by the reducing gas from the organic binder 220 surrounding it, so that the iron 110 in the adsorbent 10 after calcination has a structure in which it is contained within the porous structure of the second carbide 120. Therefore, the adsorption capacity of the adsorbent 10 can be increased.

[0063] Furthermore, many reducing gases are difficult to handle due to their explosive and flammable nature. Therefore, an inert gas may be included in the calcination of the granules 20 to dilute and exhaust the generated reducing gas. Examples of inert gases include nitrogen gas or argon gas. When using an inert gas, for example, nitrogen gas can be flowed through the calcination furnace so that the carbon monoxide concentration inside the furnace is between 1% and 20%.

[0064] Furthermore, a reducing atmosphere can be formed not only using reducing gases generated from the organic binder 220, but also using other reducing gases such as carbon monoxide, hydrogen gas, hydrogen sulfide gas, sulfur dioxide gas, hydrocarbon gases, or mixtures thereof. However, even in this case, the amount of reducing gas can be reduced compared to conventional methods for manufacturing adsorbents.

[0065] The heating temperature during the calcination of the granules 20 is 400°C to 1200°C, preferably 400°C to 900°C, and more preferably 600°C to 900°C. The heating time is 1 minute to 10 hours, preferably 10 minutes to 5 hours. In the method for producing the adsorbent 10 according to this embodiment, the iron compound 210 can be reduced using the reducing gas generated from the organic binder 220, making it possible to lower the heating temperature or shorten the heating time compared to conventional methods for producing adsorbents.

[0066] By calcining the granules 20, the carbides 200 are transformed into first carbides 100, the iron compounds 210 into iron 110, and the organic binder 220 into second carbides 120.

[0067] Through the above firing process (S140), an adsorbent material 10 containing iron 110 is produced.

[0068] As mentioned above, for the sake of explanation, the first carbide 100 and the second carbide 120 contained in the generated adsorbent 10 were distinguished based on the difference in raw materials. However, both the first carbide 100 and the second carbide 120 are carbides (properly different from carbide 200), and they do not need to be clearly distinguished in the adsorbent 10. In other words, the adsorbent 10 can be said to be an iron-containing carbide. However, the manufacturing method of the adsorbent 10 differs from that of conventional iron-containing carbides, and although the mechanism is not clear, it has different properties from conventional iron-containing carbides.

[0069] [2-5. Evaluation of Adsorbent 10] The adsorbent 10 according to the present invention, manufactured by the manufacturing method described above, reduces iron elution and becomes an adsorbent with excellent adsorption properties. The adsorption properties of the adsorbent 10 can be evaluated by, for example, the following measurements.

[0070] [2-5-1. Amount of phosphorus adsorbed] The adsorbent 10 according to this embodiment can adsorb phosphorus, arsenic, or lead, among other things. In particular, the adsorbent 10 exhibits excellent phosphorus adsorption properties. The phosphorus adsorption capacity of the adsorbent 10 can be evaluated by a batch test. The batch test is a method of calculating the amount of phosphorus adsorbed from the difference in concentration between the added phosphorus solution and the supernatant after the reaction. The phosphorus solution is obtained by dissolving potassium dihydrogen phosphate (KH2PO4) in water. In the following examples, the concentration of the phosphorus solution will be expressed as the amount of P per 1 L of water. That is, the concentration of a phosphorus solution obtained by dissolving 200 mg of P in 1 L of water will be expressed as 200 mg / L. Furthermore, the amount of phosphorus adsorbed by the adsorbent 10 will be expressed as the amount of phosphorus adsorbed per 1 g of adsorbent (amount of adsorbed phosphorus (mg-P) / 1 g of adsorbent).

[0071] [2-5-2. Specific surface area] Specific surface area is the surface area per unit quantity and is one of the important parameters in porous materials. Specific surface area is related to the surface structure of the adsorbent 10 and can be said to be one of the parameters that determine its adsorption characteristics. The specific surface area of ​​the adsorbent 10 can be measured, for example, using the gas adsorption method based on the BET formula (BET method).

[0072] The BET method allows for the calculation of the specific surface area (surface area per gram of sample) of a sample by measuring the adsorption of gas. Specifically, the BET method determines the specific surface area from the adsorption isotherm. That is, the amount of adsorbed gas is determined based on the BET formula, and the specific surface area is calculated by multiplying this by the area occupied by one molecule of the adsorbed gas on the surface. Examples of adsorbed gases include nitrogen gas, argon gas, krypton gas, carbon monoxide gas, or carbon dioxide gas, and the amount of adsorption can be measured from the pressure or volume change of the gas to be adsorbed. A specific measurement using the BET method involves, for example, vacuum degassing at a temperature of 120°C as a pretreatment, adsorbing nitrogen gas as the adsorbed gas, and calculating the specific surface area from the BET formula.

[0073] The specific surface area described herein is typically the specific surface area measured by the BET method using nitrogen gas as the adsorption gas, but it may also be the specific surface area measured by a method other than the BET method.

[0074] The specific surface area of ​​the adsorbent 10 is 100 m². 2 / g or more 500m 2 It is less than or equal to / g, preferably 100m 2 / g or more 400m 2 It is less than or equal to / g, and more preferably 150m 2 / g or more 400m 2 It is less than or equal to / g. If the specific surface area of ​​the adsorbent 10 is too small, it will not be possible to secure a sufficient amount of adsorption, and the adsorption characteristics of the adsorbent 10 will deteriorate. On the other hand, if the specific surface area of ​​the adsorbent 10 is too large, the density will decrease, and the strength of the adsorbent 10 will decrease. In other words, the adsorbent 10 will not be able to maintain a constant shape and will become brittle. Therefore, it is preferable that the specific surface area of ​​the adsorbent 10 be within the above range.

[0075] [2-5-3. Total pore volume] Total pore volume, along with specific surface area, is one of the important parameters in porous materials. Total pore volume is related to the adsorption capacity of the adsorbent 10 and can be said to be one of the parameters that determine the adsorption characteristics of the adsorbent 10. The total pore volume of the adsorbent 10 is the sum of the pore volumes calculated from the pore volume distribution, which shows the pore diameter and pore volume of the adsorbent 10.

[0076] Pores can be classified, for example, by their pore diameter d, into macropores (d > 50 nm), mesopores (2 nm ≤ d ≤ 50 nm), or micropores (d < 2 nm). Typically, macropores can be measured using the mercury intrusion method based on the Washburn formula, mesopores using the gas adsorption method based on the BJH formula (BJH method), and micropores using the gas adsorption method based on the HK formula (HK method), but this is not limited to these methods.

[0077] In the mercury intrusion method, the pore size d can be calculated from the pressure of the mercury injected into the sample, based on the Washburn formula. Similarly, in the gas adsorption method, the pore size d can be calculated from the pressure of the gas injected into the sample, based on the BJH or HK formulas. Therefore, by varying the pressure of the injected mercury or gas and measuring the amount of adsorption in the sample, a pore volume distribution showing the pore volume relative to the pore size d can be obtained.

[0078] In this specification, the total pore volume is defined as the cumulative volume of pores where the pore diameter d is in the range of 7.5 nm to 110,000 nm.

[0079] The total pore volume of the adsorbent material 10 is 1000 mm³. 3 / g or more 3000mm 3 It is less than or equal to / g, preferably 1000mm 3 / g or more 2700mm 3 It is less than or equal to / g, and more preferably 1000mm 3 / g or more 2500mm 3 It is less than or equal to / g. If the total pore volume of the adsorbent 10 is too small, it will not be possible to secure a sufficient amount of adsorption, and the adsorption characteristics of the adsorbent 10 will deteriorate. On the other hand, if the total pore volume of the adsorbent 10 is too large, the specific surface area will decrease, and the adsorption characteristics of the adsorbent 10 will deteriorate. Therefore, it is preferable that the total pore volume of the adsorbent 10 is within the above range.

[0080] [2-5-4. Iron content] The adsorbent 10, by containing iron 110 in its carbide, exhibits a significantly increased adsorption capacity compared to conventional activated carbon. Therefore, the iron 110 content of the adsorbent 10 is related to its adsorption capacity and can be considered one of the parameters that determine the adsorption characteristics of the adsorbent 10. The amount of iron 110 contained in the adsorbent 10 can be measured, for example, using inductively coupled plasma mass spectrometry (ICP-MS).

[0081] ICP-MS is a method that uses argon plasma as an ion source to ionize elements contained in a sample, and then separates and detects the ions based on their mass-to-charge ratio. The elements can be identified from the mass-to-charge ratio of the detected ions, and the amount of each element can be measured by counting the detected ions.

[0082] The iron 110 content of the adsorbent 10 is the ratio of the amount of iron 110 to the amount of adsorbent 10. The iron 110 content of the adsorbent 10 can be calculated from the amount of iron 110 measured by the ICP-MS described above and the amount of adsorbent 10 used for the measurement.

[0083] The iron content of the adsorbent 10 is 5% to 35%, preferably 5% to 30%, and more preferably 5% to 25%. If the iron content of the adsorbent 10 is too low, the effect of iron will not be apparent, and the adsorption characteristics of the adsorbent 10 will decrease. On the other hand, if the iron content of the adsorbent 10 is too high, the iron will dissolve when adsorbing phosphorus. Therefore, it is preferable that the iron content of the adsorbent 10 be within the above range.

[0084] [2-5-5. Organic carbon content] In the method for manufacturing the adsorbent 10 described above, pellet-shaped granules 20 can be stably produced by kneading the organic binder 220. Furthermore, the reducing gas generated from the organic binder 20 in the granules 20 can sufficiently reduce the iron compound 210 to iron 110. Therefore, the organic binder 220 is a very important material in the production of the adsorbent 10. Since the organic binder 220 is transformed into a second carbide 120 by the calcination process (S140), it is difficult to directly quantify the organic binder 220 by measuring the adsorbent 10. However, the inventors have found that the content of organic carbon contained in the carbide of the adsorbent 10 is related to the adsorption characteristics of the adsorbent 10. Although the mechanism of this relationship is not entirely clear, it is presumed that the organic carbon contained in the carbide of the adsorbent 10 is due to the second carbide 120. Therefore, by measuring the organic carbon content in the carbide of the adsorbent 10, the content of the secondary carbide 120 in the carbide of the adsorbent 10 can be determined, and it can be identified that the adsorbent 10 was manufactured using the organic binder 220. In this respect, the organic carbon content in the carbide of the adsorbent 10 can be said to be one of the parameters that determine the adsorption characteristics of the adsorbent 10.

[0085] The organic carbon content in the carbide of the adsorbent 10 can be calculated by subtracting the inorganic carbon content from the total carbon content. The total carbon content can be calculated, for example, based on the amount of carbon dioxide generated when the sample is burned. The inorganic carbon content can be calculated, for example, based on the amount of carbon dioxide released from carbonates, etc., when the sample is heated in an acidic state. The combustion temperature when measuring the total carbon content is preferably higher than the firing temperature of the firing process (S140). For example, if the firing temperature of the firing process (S140) is 850°C, the combustion temperature when measuring the total carbon content can be 900°C. Furthermore, the heating temperature when measuring the inorganic carbon content is preferably lower than the firing temperature of the firing process (S140). For example, the heating temperature when measuring the inorganic carbon content is 200°C. By using a total organic carbon meter, the total carbon content and the inorganic carbon content can be measured, and the organic carbon content can be calculated.

[0086] The organic carbon content in the carbide of the adsorbent 10 is the ratio of the amount of organic carbon to the amount of carbide in the adsorbent 10. The organic carbon content in the carbide of the adsorbent 10 can be calculated from the calculated organic carbon content and the measured total carbon content.

[0087] The organic carbon content in the carbide of the adsorbent 10 is 30% or more and 85% or less, preferably 30% or more and 75% or less, and more preferably 35% or more and 70% or less.

[0088] As described above, the adsorbent 10 according to the embodiment of the present invention does not require the use of special manufacturing equipment, thus reducing manufacturing costs. Furthermore, the adsorbent 10 has different parameters compared to conventional adsorbents and exhibits superior adsorption characteristics. In particular, the adsorbent 10 within the above-mentioned parameter range, for example, the organic carbon content in the carbide is 30% to 85%, and the specific surface area is 100 m². 2 / g or more 500m 2 The total pore volume is less than / g and less than 1000 mm³. 3 / g or more 3000mm 3Adsorbent 10 with a concentration of less than / g has particularly excellent adsorption properties. Therefore, the specific parameters and adsorption properties of adsorbent 10 will be described with reference to examples. [Examples]

[0089] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0090] <Example 1> A mixture was obtained by mixing 300g of amorphous charcoal (as a carbonized material) and 83g of iron oxide for 3 minutes. The moisture content of the charcoal was 7.5%, and the solid component of the charcoal was 300 × 92.5% = 277.5g. Therefore, the ratio of the amount of solid component of the charcoal to the amount of iron oxide was 277.5:83 = 100:30.

[0091] Next, the mixture was placed in a kneader (Dalton Co., Ltd., model: KDRJ-10), 500g of molasses was added over 2 minutes at room temperature, and the mixture was kneaded for 30 minutes to obtain a paste. The moisture content of the molasses was 30%, and the solid components of the molasses were 500 × 70.0% = 350.0g. The ratio of the solid components of the charcoal to the solid components of the molasses was 277.5:350 = 100:126.1.

[0092] Next, the paste was fed into a granulator (manufactured by Dalton Co., Ltd., model: F-5), and under conditions of a rotation speed of 112 rpm, pellet-shaped granules with a diameter of 6 mm and a height of 9 mm were obtained.

[0093] Next, using a double-row, three-zone tubular furnace unit equipped with quartz tubes (manufactured by Asahi Rika Seisakusho Co., Ltd.), 50 g of the granulated material obtained was calcined at 750°C for 3 hours under a nitrogen atmosphere to obtain 25 g of adsorbent A.

[0094] The amount of phosphorus adsorbed by adsorbent A was evaluated using a batch method. 0.1 g of adsorbent A was added to 50 ml of a 200 mg / L phosphorus solution, and the mixture was shaken horizontally at 23°C and 100 rpm until equilibrium concentration was reached, after which it was filtered. The phosphorus adsorbed by adsorbent A was calculated to be 27.2 mg-P / g by analyzing the phosphorus concentration of the filtrate using molybdenum blue spectrophotometry. Furthermore, no disintegration of adsorbent A was observed after the evaluation of phosphorus adsorption, indicating high strength in water. In addition, the amount of iron eluted was 9.4 ppm, indicating that iron elution from adsorbent A was reduced.

[0095] <Example 2> Except for setting the firing temperature to 800°C, the conditions were the same as in Example 1, and 24 g of adsorbent B was obtained.

[0096] The amount of phosphorus adsorbed by adsorbent B was evaluated under the same conditions as in Example 1. The amount of phosphorus adsorbed by adsorbent B was 37.9 mg-P / g. Furthermore, no disintegration of adsorbent B was observed after the evaluation of phosphorus adsorption, indicating high strength in water. In addition, the amount of iron leached was 10.4 ppm, indicating that the leaching of iron from adsorbent B was reduced.

[0097] <Example 3> Except for setting the firing temperature to 850°C, the conditions were the same as in Example 1, and 22 g of adsorbent C was obtained.

[0098] The amount of phosphorus adsorbed by adsorbent C was evaluated under the same conditions as in Example 1. The amount of phosphorus adsorbed by adsorbent C was 39.2 mg-P / g. Furthermore, no disintegration of adsorbent C was observed after the evaluation of phosphorus adsorption, indicating high strength in water. In addition, the amount of iron leached was 9.8 ppm, indicating that the leaching of iron from adsorbent C was reduced.

[0099] <Comparative Example> To confirm the effect of the adsorbent 10 according to this embodiment, a commercially available activated carbon was used as an example of a conventional adsorbent, and the same evaluation as in Examples 1 to 3 was performed. Specifically, the amount of phosphorus adsorbed by the activated carbon was evaluated using a batch method. 0.5 g of activated carbon (granular Shirasagi WH2x, manufactured by Osaka Gas Chemical Co., Ltd.) and 250 ml of a 200 mg / L phosphorus solution were used. The amount of phosphorus adsorbed by the activated carbon was 3.5 (mg-P / g).

[0100] Based on the above, a comparison of adsorbents A to C obtained in Examples 1 to 3 with the activated carbon of the comparative example revealed that the adsorbent 10 according to this embodiment significantly improves the amount of phosphorus adsorbed.

[0101] Furthermore, in order to compare the differences in properties between adsorbents A to C obtained in Examples 1 to 3 and the activated carbon of the comparative example, the specific surface area, total pore volume, iron content, and organic carbon content were evaluated for each of the adsorbents A to C and the activated carbon.

[0102] The specific surface area was measured using a fully automatic specific surface area measuring device (model: HM model-1201) manufactured by Mountec Co., Ltd.

[0103] Pore ​​size distribution was measured using a fully automated pore size distribution analyzer (model: PoreMaster 33P) manufactured by Quantachrome. The total pore size volume was calculated by integrating the pore size volumes within the range of pore size between 7.5 nm and 110,000 nm in the measured pore size distribution.

[0104] The iron content was measured by heating the adsorbent in a 10% hydrochloric acid solution at 100°C for 15 minutes, and then measuring the iron content of the adsorbent using ICP-MS. The iron content percentage of the adsorbent was calculated from the amount of adsorbent used and the measured iron content.

[0105] The organic carbon content was measured using a total organic carbon meter manufactured by Shimadzu Corporation. The organic carbon content relative to the carbide of the adsorbent was calculated based on the measured organic carbon content and total carbon content.

[0106] Table 1 shows the evaluation results for adsorbents A to C and activated carbon.

[0107] [Table 1]

[0108] Table 1 shows that, compared to activated carbon, adsorbents A-C have a smaller specific surface area and a larger total pore volume. Furthermore, compared to activated carbon, adsorbents A-C have a lower organic carbon content in their carbides. It is presumed that these properties significantly improve the phosphorus adsorption capacity of adsorbents A-C. [Explanation of Symbols]

[0109] 10: Adsorbent, 20: Granules, 100: Primary carbide, 110: Iron, 120: Secondary carbide, 200: Carbide, 210: Iron compound, 220: Organic binder

Claims

1. It contains porous carbide and iron, The organic carbon content in the carbide is 30% or more and 85% or less. The iron content is 15% or more and 35% or less. Specific surface area of ​​100 m² ２ / g or more 237m ２ / g or less, Total pore volume is 1000 mm ３ / g or more 1978mm ３ Adsorbent with a value of less than / g.

2. The adsorbent according to claim 1, wherein the content of the organic carbon in the carbide is 50% or more and 85% or less.

3. The adsorbent according to claim 1 or claim 2, wherein the pellet is substantially cylindrical.

4. The adsorbent according to any one of claims 1 to 3, wherein the amount of phosphorus adsorbed is 30 mg-P / g or more.

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