JP7323345B2 - Adsorbent and manufacturing method thereof - Google Patents

Description

The present invention relates to adsorbents. In particular, the present invention relates to adsorbents that adsorb substances such as phosphorus and arsenic.

In order to reduce the amount of carbon dioxide in the atmosphere, techniques for artificially collecting carbon dioxide and storing it underground are known. For example, by using biomass such as trees and agricultural products to absorb carbon dioxide in the atmosphere, the carbon dioxide can be fixed as organic carbon. However, since such biomass is an organic matter, even if it is stored in the ground as it is, it will putrefy or decompose and release carbon dioxide again into the atmosphere. On the other hand, when biomass is heated in a state in which oxygen is shut off, oxygen atoms and hydrogen atoms are desorbed, and carbides composed of carbon and ash can be produced. Since this carbide is a mass of carbon, it will not burn unless heated to a high temperature in the presence of oxygen. That is, carbide is very stable in the environment (in the ground) and hardly decomposed.

Carbon dioxide can be fixed in the social environment by replacing these carbides with industrial products such as construction materials. Furthermore, by burying these carbonized substances in the ground, carbon dioxide can be isolated and stored in the ground. In other words, promoting the use of carbide leads to reduction of carbon dioxide in the atmosphere.

Charcoal also has the effect of improving the quality of soil. However, considering the cost of producing charcoal, the use of charcoal just for soil improvement is not worth the production cost.

On the other hand, carbides are known to be porous and therefore have a very large surface area. Taking advantage of this large surface area, carbides are used as adsorbents for various substances. For example, Patent Document 1 describes a phosphorus adsorbent using a calcium-supporting carbide. Further, Patent Document 2 describes a technique for adsorbing phosphorus (phosphate ions) in water by using a carbide containing iron as a phosphorus adsorbent. In addition, Non-Patent Document 1 describes a method of reducing carbonized biomass to agricultural land.

In this way, not only for improving the soil quality of soil, for example, carbonized matter that can suppress environmental pollution by adsorbing a specific substance, or applying the specific substance to other uses Demand for carbides capable of

JP-A-2007-75706 JP-A-2003-88878

Simple carbonization of biomass and carbon-storing vegetables for regional development COOL VEGE TM, Journal of High Temperature Society, Vol.37, No.2, p.37-42

However, the phosphorus adsorbent of Patent Document 1 requires the use of a material containing a large amount of silicon, such as rice husks or diatomaceous earth. In the phosphorus adsorbent of Patent Document 2, it is necessary to use carbonized waste containing magnetic materials such as magnetic card charcoal and magnetic tape charcoal. When using a material containing a large amount of silicon or a magnetic material, there is a limit to the amount of phosphorus adsorbent that can be produced, and there is a limit to the allowable amount of substances such as phosphorus that can be adsorbed. In addition, the carbonized biomass described in Non-Patent Document 1 alone does not have sufficient phosphorus adsorption performance.

One embodiment of the present invention has been made in view of the above problems, and provides an adsorbent that can be manufactured using various materials and has an excellent adsorption capacity for a target substance. The challenge is to

An adsorbent according to one embodiment of the present invention comprises a porous material, metallic iron inside the pores of the porous material, and iron oxide or iron sulfide on the surface of the porous material.

The metallic iron may be fibrous.

An adsorbent according to one embodiment of the present invention comprises a porous material and fibrous metallic iron inside the pores of the porous material.

Iron oxide or iron sulfide may be present on the surface of the porous material.

The fibrous metallic iron may include a plurality of linear bodies.

The metallic iron may be crystalline.

The metallic iron may have crystallinity exhibiting a diffraction peak attributed to iron when the adsorbent is pulverized and subjected to XRD analysis.

The iron oxide or iron sulfide may be granular.

The iron oxide or iron sulfide may be crystals having a particle size of 50 μm or less.

A pore size of the pores in a cross section orthogonal to a direction in which the pores of the porous material extend may be 100 μm or less.

The particle size of the porous material may be 10 mm or less.

The iron oxide may include at least one of wustite, hematite, maghematite, and magnetite.

The iron sulfide may include at least one of ferric sulfide, ferrous sulfide, and iron disulfide.

The porous material may be carbonized material obtained by carbonizing biomass.

The porous material may be carbonized lignocellulose.

Said lignocellulose is found in wood, particleboard, sawdust, agricultural waste, sewage, silage, grass, rice husk, bagasse, cotton, jute, hemp, flax, bamboo, sisal, abaca, straw, wheat straw, corn cob, corn. It may be one or more materials selected from the group consisting of stover, switchgrass, alfalfa, hay, palm hair, seaweed, algae, and mixtures thereof.

ADVANTAGE OF THE INVENTION According to one embodiment of the present invention, it is possible to provide an adsorbent that can be manufactured using various materials and that has an excellent adsorption capacity for a target substance.

It is a figure which shows the cross-section of the adsorption material which concerns on one Embodiment of this invention. It is a cross-sectional SEM image of the adsorbent according to one embodiment of the present invention. 4 shows the result of composition analysis of fibrous metallic iron existing inside the pores of the porous material in the adsorbent according to one embodiment of the present invention. 1 is a surface SEM image of a porous material in an adsorbent according to one embodiment of the present invention. 4 shows the results of composition analysis of fibrous deposits present on the surface of the porous material in the adsorbent according to one embodiment of the present invention. 5 is an enlarged SEM image of the surface of the porous material shown in FIG. 4 in the adsorbent according to one embodiment of the present invention. 4 shows the results of composition analysis of granular substances present on the surface of the porous material in the adsorbent according to one embodiment of the present invention. 4 shows composition analysis results of fibrous substances present on the surface of the porous material in the adsorbent according to one embodiment of the present invention. 5 is an enlarged SEM image of the surface of the porous material shown in FIG. 4 in the adsorbent according to one embodiment of the present invention. FIG. 10 is a compositional analysis result of the substance shown in the SEM image of FIG. 9. FIG. It is a figure which shows the XRD analysis result of the adsorbent which concerns on one Embodiment of this invention. It is a flow chart which shows a manufacturing method of adsorbent concerning one embodiment of the present invention. 1 is a cross-sectional view showing the pore shape of a porous material used for an adsorbent according to one embodiment of the present invention; FIG.

Hereinafter, an adsorbent and a method for producing the adsorbent according to an embodiment of the present invention will be described with reference to the drawings. However, the adsorbent and method of making the adsorbent according to an embodiment of the present invention can be implemented in many different ways and should not be construed as limited to the description of the examples provided below. In the drawings referred to in this embodiment, the same parts or parts having similar functions are denoted by the same reference numerals or alphabetical characters after the same reference numerals, and repeated description thereof will be omitted.

In the following embodiments, a carbonized material obtained by carbonizing wood is exemplified as the porous material used for the adsorbent, but the configuration is not limited to this. For example, the carbonized material may be carbonized organic matter other than wood. Also, the porous material may be a porous member other than carbide. Also, the techniques of different embodiments can be combined unless there is a particular technical contradiction.

In the following embodiments, the pore size of the porous material is referred to as the pore size, and the size of the particulate matter is referred to as the particle size. The pore diameter refers to the size of a pore in a cross section perpendicular to the direction in which the pore extends, unless otherwise specified. However, if the pore does not have a longitudinal dimension, the pore diameter refers to the size of the pore in any given cross section. The pore diameter may be the circle-equivalent diameter of the pores in any cross-section, or may be the maximum diameter or average diameter in the cross-section. Similarly, the particle diameter may be the equivalent circle diameter of the particulate matter in any cross-sectional view or projection plane, or may be the maximum diameter or average diameter in the cross-sectional view or projection plane.

[Structure of adsorbent 10]
The structure of the adsorbent 10 according to this embodiment will be described with reference to FIGS. 1 to 11. FIG. In the present embodiment, a configuration in which a carbonized material obtained by carbonizing wood is used as the porous material 100 used for the adsorbent 10 will be described.

FIG. 1 is a diagram showing a cross-sectional structure of an adsorbent according to one embodiment of the present invention. The cross-sectional view shown in FIG. 1 is a cross-sectional view perpendicular to the direction in which the pores 200 of the porous material 100 extend. That is, each hole 200 extends in the depth direction of the drawing.

As shown in FIG. 1, the adsorbent 10 has a porous material 100, metallic iron 600, iron oxide 800, and iron sulfide 900. As shown in FIG. The metallic iron 600 is contained inside the pores 200 (macropores 200 described later) of the porous material 100 . The shape of each metallic iron 600 is fibrous. The fibrous metallic iron 600 is composed of a plurality of filamentous bodies 610 . One end or both ends of the linear body 610 may be attached to the inner wall 201 . Alternatively, one end or both ends of linear body 610 may be fixed to inner wall 201 . Metal iron 600 is held inside hole 200 by fixing one end or both ends of linear body 610 to inner wall 201 . A large number of linear bodies 610 are present inside the holes 200, so that the metallic iron 600 forms a fibrous shape. That is, in the following description, the filamentous body 610 means part of the fibrous metallic iron 600 . For convenience of explanation, the metal iron 600 inside the hole 200 drawn in the lower part of FIG. 1 is omitted.

Since the metallic iron 600 inside the hole 200 is fibrous, the inside of the hole 200 is not completely filled with the metallic iron 600, and the space where the metallic iron 600 does not exist extends continuously in the extending direction of the hole 200. there is Moreover, since the metallic iron 600 is fibrous, the metallic iron 600 exists not only in the inner wall of the hole 200 but also in the space inside the hole 200 . Here, since the hole 200 and the metal iron 600 extend in the depth direction of the drawing, when the hole 200 is viewed in the extension direction of the hole 200, the metal iron 600 seems to fill the internal space of the hole 200. .

The hole diameter of the hole 200 in the cross section orthogonal to the extending direction of the hole 200 is 100 μm or less, 50 μm or less, 30 μm or less, or 20 μm or less. The length of linear body 610 from one position to the other position on the inner wall of hole 200 is 100 μm or less, 50 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. The thickness of the linear body 610 (the thickness of the linear body 610 in the cross section orthogonal to the extending direction (or longitudinal direction) of the metal iron 600) is 10 μm or less, 5 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less. is. In addition, the particle size of the porous material 100 in the cross section orthogonal to the extending direction of the hole 200 is 10 mm or less, 5 mm or less, 3 mm or less, or 2 mm or less. Although the details will be described later, it is considered that the linear body 610 is undergoing crystal growth. That is, unlike, for example, a linear or fibrous metal formed by processing a metal material, the length and thickness are very small as described above.

Iron oxide 800 and/or iron sulfide 900 are present at least on the surface of the porous material 100 . Iron oxide 800 is fibrous. Iron sulfide 900 is granular. Iron oxide 800 is formed more extensively than iron sulfide 900. The equivalent circle diameter of iron sulfide 900 is 50 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less.

In this embodiment, the configuration in which the iron oxide 800 is fibrous and the iron sulfide 900 is granular is exemplified, but the present invention is not limited to this configuration. For example, iron oxide 800 may be granular and iron sulfide 900 fibrous, or both iron oxide 800 and iron sulfide 900 may be fibrous or granular. Further, in the present embodiment, the metallic iron 600 exists only inside the pores 200, and the iron oxide 800 and the iron sulfide 900 exist only on the surface of the porous material 100, but the present invention is not limited to this construction. Metallic iron 600 may be present on the surface of the porous material 100 . Similarly, iron oxide 800 and iron sulfide 900 may be present inside the pores 200 .

[Material of each member]
As the porous material 100 used for the adsorbent 10, a carbonized material obtained by carbonizing biomass can be used, and typically a carbonized material obtained by carbonizing lignocellulose can be used. As lignocellulose, wood, particleboard, sawdust, agricultural waste, sewage, silage, grass, rice husk, bagasse, cotton, jute, hemp, flax, bamboo, sisal, abaca, straw, wheat straw, maize cob, maize sto One or more materials selected from the group consisting of grass, switchgrass, alfalfa, hay, palm hair, seaweed, algae, and mixtures thereof can be used.

At least one of wustite, hematite, maghematite, and magnetite can be used as the iron oxide 800 on the surface of the porous material 100 . At least one of ferric sulfide, ferrous sulfide, and iron disulfide can be used as the iron sulfide 900 on the surface of the porous material 100 .

[Results of analysis of adsorbent 10]
The adsorbent 10 shown in FIG. 1 will be described in detail using a scanning electron microscope (SEM) image of the adsorbent 10 actually produced. FIG. 2 is a cross-sectional SEM image of an adsorbent according to one embodiment of the present invention. As shown in FIG. 2, fibrous metallic iron 600 is present inside the hole 200 shown in the center. The fibrous metallic iron 600 is composed of a plurality of filamentous bodies 610 . In FIG. 2, a region corresponding to the inner wall of hole 200 is indicated by dotted line 3 . The length of each linear body 610 in fibrous metal iron 600 is smaller than the hole diameter of hole 200 . It should be noted that the mark in which a square and a cross are overlapped in FIG. 2 and the numbers in the vicinity thereof are merely those displayed on the measurement screen, and do not specify the configuration according to the invention.

The pore diameter of the pores 200 of the porous material 100 in this embodiment is 100 μm or less, and the length of the linear body 610 is also 100 μm or less. In the example of FIG. 2, the hole diameter of hole 200 is about 20 μm, and the length of linear body 610 is not less than 10 μm and not more than 20 μm. Here, since the fibrous metallic iron 600 also extends in the extending direction of the hole 200, the longest continuous length of the metallic iron 600 may exceed 100 μm.

FIG. 3 shows the results of composition analysis of the region of frame 601 in linear body 610 of FIG. FIG. 3 is a compositional analysis result of fibrous metallic iron existing inside the pores of the porous material in the adsorbent according to one embodiment of the present invention. The composition analysis of FIG. 3 is the analysis result measured by the energy dispersive X-ray spectroscopy (EDS) attached to the SEM apparatus.

As shown in FIG. 3, as a result of EDS analysis of the linear body 610 of FIG. 2, iron (Fe) and carbon (C) were detected. Here, carbon (C) originates from the porous material contained in the vicinity of the frame 601 and does not originate from the linear body 610 . That is, it was confirmed that the linear body 610 was iron (that is, zero-valent iron).

FIG. 4 is a surface SEM image of a porous material in an adsorbent according to one embodiment of the present invention. As shown in FIG. 4, it was confirmed that the surface of the porous material 100 had granular deposits and fibrous deposits. Although the details will be described later, it has been confirmed that the particulate deposit is iron sulfide 900 and the fibrous deposit is iron oxide 800.

FIG. 5 shows the results of composition analysis of the frame 801 region of the fibrous deposits (iron oxide 800) in FIG. FIG. 5 shows composition analysis results of fibrous deposits present on the surface of the porous material in the adsorbent according to one embodiment of the present invention. As a result of EDS analysis of the fibrous deposit (iron oxide 800) of FIG. 4, iron (Fe), oxygen (O) and carbon (C) were detected as shown in FIG. That is, it was confirmed that the fibrous deposit was iron oxide.

FIG. 6 is an enlarged SEM image of the surface of the porous material 100 in the adsorbent according to one embodiment of the present invention. FIG. 6 is an enlarged SEM image of a portion of the surface of the porous material 100 of FIG. As shown in FIG. 6, on the surface of the porous material 100, there are particulate deposits with a particle size of 10 μm or less. It should be noted that the mark in which a square and a cross overlap in FIG. 6 and the numbers in the vicinity thereof are merely those displayed on the measurement screen, and do not specify the configuration according to the invention.

FIG. 7 shows the results of the composition analysis of the frame 901 region of the granular deposits (iron sulfide 900) in FIG. FIG. 7 shows the results of composition analysis of substances existing on the surface of the porous material in the adsorbent according to one embodiment of the present invention. As a result of EDS analysis of the particulate deposit (iron sulfide 900) in FIG. 6, iron (Fe), sulfur (S), and carbon (C) were detected, as shown in FIG. That is, it was confirmed that the particulate deposit was iron sulfide.

FIG. 8 shows the results of composition analysis of the frame 803 region of the fibrous deposits (iron oxide 800) in FIG. FIG. 8 shows the results of composition analysis of substances existing on the surface of the porous material in the adsorbent according to one embodiment of the present invention. As a result of EDS analysis of the fibrous deposit (iron oxide 800) of FIG. 6, iron (Fe), oxygen (O) and carbon (C) were detected as shown in FIG. That is, it was confirmed that the fibrous deposit was iron oxide.

FIG. 9 is an enlarged SEM image of the surface of the porous material in the adsorbent according to one embodiment of the present invention. FIG. 9 is an enlarged SEM image of fibrous deposits (iron oxide 810) present adjacent to iron sulfide 900 on the surface of porous material 100 of FIG. As shown in FIG. 9, the deposits (iron oxide 810) that look fibrous at low magnification (magnification shown in FIG. 6) were confirmed to be very small granular substances linked together. It should be noted that the mark in which a square and a cross are superimposed and the numbers in the vicinity thereof in FIG. 9 are merely those displayed on the measurement screen and do not specify the configuration according to the invention.

FIG. 10 shows the results of composition analysis of the frame 811 region of the granular iron oxide 810 of FIG. As shown in FIG. 10, as a result of EDS analysis of the granular iron oxide 810 of FIG. 9, iron (Fe), oxygen (O), and carbon (C) were detected.

FIG. 11 is a diagram showing an X-ray diffraction (XRD; X-Ray Diffraction) analysis result of an adsorbent according to one embodiment of the present invention. In order to collectively evaluate the metallic iron 600 inside the pores 200 of the porous material 100 and the iron oxide 800 and iron sulfide 900 on the surface of the porous material 100, the adsorbent 10 was pulverized to a particle size of 100 μm or less. XRD analysis was performed using As shown in FIG. 11, XRD analysis confirmed peaks attributable to iron (Fe), iron oxide (wustite (FeO)), and iron sulfide (FeS).

From the results of FIGS. 2 to 10 and the results of FIG. 11, the metallic iron 600 inside the pores 200 of the porous material 100 is iron having crystallinity, and the iron oxide 800 on the surface of the porous material 100 has crystallinity. It was confirmed that the iron sulfide 900 on the surface of the porous material 100 is crystalline iron sulfide.

As described above, in the adsorbent 10 according to the present embodiment, the fibrous metallic iron 600 having crystallinity exists inside the pores 200 of the porous material 100, and the surface of the porous material 100 has crystallinity. It has a composition in which iron oxide 800 and iron sulfide 900 are present. Although the detailed manufacturing method of the adsorbent 10 will be described later, it is necessary to perform a high-temperature heat treatment (reduction treatment) in order to make the zerovalent iron exist inside the pores 200 . If the metal iron 600 inside the pores 200 is oxidized or sulfided by this reduction treatment, the adsorption performance of the adsorbent 10 is lowered. Therefore, it is preferable to suppress oxidation or sulfurization of the metallic iron 600 inside the holes 200 during the reduction treatment. In this embodiment, no iron oxide or iron sulfide was found inside the pores 200 of the porous material 100 within the scope of the analysis. This is due to the formation of granular iron sulfide 900 and fibrous iron oxide 800 (a string of very small granular substances) on the surface of the porous material 100; It is considered that the oxidation or sulfurization of the metallic iron 600 provided inside the hole 200 is suppressed by the oxidation or sulfurization. In addition, the formation of iron sulfide and iron oxide suppresses the reaction between the carbide on the surface and oxygen in the air to some extent, preventing the carbide from burning due to the heat of reaction with oxygen immediately after production. It is considered that

In addition, since the metallic iron 600 inside the pores 200 of the porous material 100 is fibrous, the surface area of the metallic iron 600 inside the pores 200 can be increased, and the adsorption performance of the adsorbent 10 can be improved. can be done. Further, since the metallic iron 600 is fibrous, the surface area of the metallic iron 600 is simply increased, and the contact area between the metallic iron and the adsorbed substance can be increased. Therefore, with the above configuration, the adsorption performance of the adsorbent 10 can be improved.

[Manufacturing method of adsorbent 10]
A method for manufacturing the adsorbent 10 according to this embodiment will be described with reference to FIGS. 12 and 13. FIG. In this embodiment, as a method of introducing the iron compound into the pores of the carbide, a method of immersing the carbide in a solution containing iron is used, and the iron compound adhering to the pores of the carbide is reduced. The manner in which the zerovalent iron particles are placed in the pores of the carbide is described.

FIG. 12 is a flow chart showing a method for manufacturing an adsorbent according to one embodiment of the invention. FIG. 13 is a cross-sectional view showing the pore shape of the porous material used for the adsorbent according to one embodiment of the present invention.

As shown in FIG. 12, organic matter is carbonized in step S101. In this embodiment, wood is used as the organic material. Carbonization of the organic matter is performed by heat treatment in an atmosphere having a lower oxygen ratio than the air atmosphere.

There are two main types of carbonization furnaces: a carbonization furnace that supplies heat necessary for carbonization from the outside is called an external heat type, and a furnace that secures heat from materials is called an internal combustion type. The external heat type cuts off oxygen for carbonization, and the internal combustion type supplies the oxygen necessary for combustion to secure the minimum amount of heat required for carbonization. So basically the process of heating at high temperature under reducing conditions is called carbonization. When organic matter is heated under reducing conditions, composition decomposition in the organic matter begins during the temperature rise (for example, about 280° C.), and oxygen and hydrogen in the organic matter are converted into gases such as carbon dioxide, carbon monoxide, hydrogen, and hydrocarbons. As it evaporates, it changes to amorphous carbon with a high carbon content. By continuing to heat at a higher temperature, oxygen and hydrogen in the organic matter are further reduced, forming a carbide composed of high-purity fixed carbon and ash. Such a change turns the organic matter into a carbide. Moisture and constituent components in the organic matter are desorbed as volatile gases, etc., and a certain amount of carbon remains. Therefore, a large number of continuous pores of various sizes are formed in the carbide formed by the carbonization of the organic matter. As the carbonization temperature rises, the carbonization progresses and the carbide formed has heat resistance (fire resistance), adsorptivity, and conductivity. A carbide formed by carbonizing organic matter is an example of the porous material 100 . In this case, the porous material 100 has electrical conductivity.

Here, the pore shape of the porous material 100 when carbide is used as the porous material 100 will be described with reference to FIG. As shown in FIG. 13, porous material 100 has macropores 200 (corresponding to pores 200 in FIG. 1), mesopores 210 and micropores 220 . The macropores 200 are pores connected to the surface of the porous material 100 . Inside the porous material 100 , the macropores 200 are subdivided to form mesopores 210 , and the mesopores 210 are subdivided to form micropores 220 . The size of the macropores 200 is 100 μm or less, 50 μm or less, 30 μm or less, or 20 μm or less. The size of the mesopores 210 is about 2 nm or more and 50 nm or less. The size of the micropores 220 is approximately 0.5 nm or more and 2 nm or less.

As shown in FIG. 12, apart from the carbonization of organic matter in step S101, a solution 120 containing iron or iron compounds is prepared in step S103. In this embodiment, an aqueous solution containing iron is used as the solution 120 . Specifically, the solution 120 includes a ferrous chloride aqueous solution (FeCl ₂ ), a ferric chloride aqueous solution (FeCl ₃ ), a ferrous nitrate aqueous solution (Fe(NO ₃ ), in which inorganic iron or an inorganic iron compound is dissolved). ₂ ), an aqueous ferric nitrate solution (Fe(NO ₃ ) ₃ ), an aqueous ferrous sulfate solution (FeSO ₄ ), or an aqueous ferric sulfate solution (Fe(SO ₄ ) ₃ ) is used. Alternatively, as the solution 120, a solution in which heme iron bound to protein as an organic iron compound is dissolved can also be used. Waste products such as animal blood containing heme iron may also be used. When these solutions are not particularly distinguished, they may simply be referred to as iron solutions. The solution 120 is not limited to the above iron solution, and may be a solution containing iron other than the above. Moreover, the solvent of the solution is not limited to water, and organic solvents such as methanol, ethanol, phenol, benzene, and hexane may be used.

At step S105, the carbide formed at step S101 is immersed in the solution 120 formed at step S103.

In step S107, the atmosphere in which the porous material 100 is immersed in the solution 120 is decompressed (degassed). Alternatively, the atmosphere may be decompressed while the porous material 100 is arranged, and then the solution 120 may be injected to immerse the porous material 100 in the solution 120 . Alternatively, a method of pressurizing after the porous material 100 is immersed and decompressed may be adopted. This decompression process can eliminate the phenomenon that air bubbles remain inside the holes. If such a phenomenon does not occur, or if such a phenomenon does not greatly affect the characteristics of the adsorbent 10, this decompression process can be omitted.

In step S109, the atmosphere pressure-reduced in step S107 is returned to atmospheric pressure, and the porous material 100 is taken out of the solution 120. FIG. As a method for removing the porous material 100 from the solution 120, a known method such as liquid removal by centrifugation can be used. In step S111, the porous material 100 impregnated with the solution 120 is dried. This drying removes the liquid contained in the solution 120 . Also, by this drying, the iron compound 111 adheres in the pores of the porous material 100 and on the surface thereof. This drying is performed while the porous material 100 is heated. Further, when drying the porous material 100, the humidity of the environment in which the porous material 100 is arranged may be adjusted. This drying may be carried out at the same time as the heat treatment of the reduction process in the next step.

In step S113 of FIG. 12, reduction treatment of the iron compound 111 adhering to the inside of the pores of the porous material 100 and the surface thereof is performed. In other words, the iron compound 111 is reduced while adhering to the inner wall of at least one of the macropores 200 , mesopores 210 and micropores 220 . The reduction treatment is performed by heat treatment in a reducing gas atmosphere. By this reduction treatment, the bivalent or trivalent iron compound 111 is reduced to zerovalent iron. Thus, the adsorbent 10 according to this embodiment is manufactured. Zero-valent iron contained in the adsorbent 10 adsorbs phosphorus, arsenic, and the like. Although the details will be described later, it is considered that a high-temperature heat treatment was performed as this reduction treatment, and fibrous metallic iron 600 as shown in FIG. 1 was formed. Note that part of the iron compound 111 is thermally decomposed by the above heat treatment, and iron oxide and/or iron sulfide are formed. A portion of the iron oxide and/or iron sulfide is then reduced to metallic iron.

The organic materials used in step S101 include raw trees (including thinned wood such as broad-leaved trees, coniferous trees, and bamboo, and forest waste), and waste materials from sawmills or wood processing factories (sawdust, bark waste, chip waste, and cut wood). ), vegetable husks, building demolition materials, or wooden scraps of furniture. The charcoal produced in step S101 is, for example, charcoal or bamboo charcoal. The charcoal may include white charcoal, black charcoal, sawdust charcoal, coconut charcoal, rice husk charcoal, and pulverized charcoal, in addition to bamboo charcoal.

The carbonization temperature of the organic substance in step S101 is 400° C. to 1200° C., 500° C. to 1100° C., 600° C. to 1000° C., or 700° C. to 900° C. The atmosphere for carbonizing the organic substance is an inert gas atmosphere such as nitrogen gas or argon gas, an oxygen-free atmosphere, a reducing atmosphere, or a reduced pressure atmosphere. When the carbonization of organic matter is carried out in a reduced pressure atmosphere, the gauge pressure is usually zero, and the gauge pressure is -101200 Pa or more and 1300 Pa or less in a low vacuum state, -101299.9 Pa or more and 101200 Pa or less in a medium vacuum state, -101299.99999 Pa or more-. It can be carried out in a high vacuum state of 101299.9 Pa or less or an ultra-high vacuum state of -101299.99999 Pa or less. In addition, when pressurizing after pressure reduction, the above treatment can be performed at a gauge pressure of -101.3 MPa or more and 0.8987 MPa or less, or -101.3 MPa or more and 0.3987 MPa or less, which is a gauge pressure with the atmospheric pressure as zero. The carbonization time of the organic substance is 10 minutes or more and 10 days or less, and 10 minutes or more and 5 hours or less. Further, when the carbonization of organic matter 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 1% or less. Carbonization of organic matter can be internal combustion or external heat, batch open or closed charcoal kiln, continuous rotary kiln or oscillating carbonization furnace, screw furnace, heating chamber, covered refractory vessel (crucible). ).

In the present embodiment, the method of obtaining the porous material 100 by carbonizing the organic matter in step S101 is illustrated, but a commercially available carbide may be used as the porous material 100 .

The mass percent concentration of iron contained in the solution 120 used in step S103 is 0.1 wt % or more and 50 wt % or less, 1 wt % or more and 40 wt % or less, or 3 wt % or more and 30 wt % or less. The time for which the porous material 100 is immersed in the solution 120 in step S103 is 10 seconds to 24 hours, 1 minute to 5 hours, or 2 minutes to 1 hour. When the pressure is reduced after immersing the carbide in a pressure vessel, or when immersing after decompression, the gauge pressure is usually -0.101 MPa or more -0.02 MPa or less, -0.101 MPa or more -0.04 MPa. or less, or -0.101 MPa or more and -0.08 MPa or less. In addition, when pressurizing after pressure reduction, the above treatment can be performed at a gauge pressure of -101.3 MPa or more and 0.8987 MPa or less, or -101.3 MPa or more and 0.3987 MPa or less, which is a gauge pressure with the atmospheric pressure as zero. In this case, the reduced pressure immersion time may be shorter than usual, and any time can be adopted after reaching a predetermined gauge pressure, but preferably 1 second or more and 1 hour or less, 10 seconds or more and 10 minutes or less, or 30 minutes or less. The time may be appropriately selected from seconds to 5 minutes.

Organic solvents such as water, methanol, ethanol, phenol, benzene, and hexane are used as solvents for the solution 120 used in step S103. In this embodiment, the method of preparing the solution 120 in step S103 is exemplified, but the solution 120 may be a commercially available product.

In addition, a dispersant may be added to the solution 120 to facilitate the dispersion of the iron ions 110 . As the dispersant, for example, a surfactant can be used. Using anionic (anionic) surfactants, cationic (cationic) surfactants, amphoteric (zwitterionic) surfactants, nonionic (nonionic) surfactants, and polymeric surfactants as surfactants can be done. As an anionic surfactant, fatty acid sodium, monoalkylsulfate, alkylpolyoxyethylenesulfate, alkylbenzenesulfonate, alkylethersulfate, triethanolamine alkylsulfate, and alkylbenzenesulfonate can be used. Alkyltrimethylammonium salts, dialkyldimethylammonium chlorides, alkylpyridium chlorides, and alkylbenzyldimethylammonium salts can be used as cationic surfactants. Alkyldimethylamine oxides and alkylcarboxybetaines can be used as amphoteric surfactants. As nonionic surfactants, polyoxyethylene alkyl ethers, fatty acid sorbitan esters, alkyl polyglucosides, fatty acid diethanolamides, octylphenol ethoxylates, and alkyl monoglyceryl ethers can be used. Polyacrylate, polystyrene sulfonate, polyvinyl alcohol, and polyethyleneimine can be used as polymeric surfactants. The concentration of the dispersant is 0.01% or more and 20% or less, or 0.01% or more and 1% or less. Note that the carbonized material is hydrophobic (non-hydrophilic) unless it is carbonized at a high temperature, so water does not easily enter inside. Therefore, by including a surfactant in the solution 120 , the solution 120 can easily permeate the inside of the porous material 100 .

In step S105, before the porous material 100 is immersed in the solution 120, the above surfactant may be supplied to the porous material 100. FIG. The surfactant may be supplied by coating the top surface of the porous material 100, or by immersing the porous material 100 in a solution containing the surfactant. Further, as in step S107, degassing may be performed while the surfactant is supplied to the porous material 100. FIG.

Also, the porous material 100 does not have to be immersed in the solution 120 . For example, by applying the solution 120 to the surface of the porous material 100 , the solution 120 may permeate into the pores of the porous material 100 .

In step S107, vibration may be applied during degassing in order to diffuse the air bubbles 130 out of the holes more efficiently. This vibration may be an ultrasonic vibration. Also, the porous material 100 may be heated during the degassing. Also, the porous material 100 may be tilted or rotated in the solution 120 during degassing. The pressure at the time of degassing is normally -0.101 MPa or more and -0.03 MPa or less as gauge pressure with atmospheric pressure as zero, and the degassing time is 10 seconds or more and 1 hour or less, or 30 seconds or more and 10 minutes or less. .

When carbide is used as the porous material 100 , the solution 120 containing the iron ions 110 may not easily permeate into the pores of the porous material 100 because the carbide is hydrophobic. In such a case, most of the porous material 100 floats on the liquid surface due to air present in the pores (macropores 200, mesopores 210, and micropores 220) of the porous material 100. FIG. Even in such a state, the air present in the pores can be pulled out of the porous material 100 and discharged out of the solution 120 by reducing the pressure. As a result, the solution 120 containing the iron ions 110 can be filled in the pores of the porous material 100 where the air bubbles 130 were present.

The above steps S105 to S111 may be repeated multiple times. Further, the steps S107 and S109 may be repeated multiple times. Further, the drying in step S111 may be performed while the pressure is reduced without going through the step of returning to the atmospheric pressure in step S109. In that case, the pressure may be returned to the atmospheric pressure after the drying, or the reduction in step S113 may be performed while the pressure is reduced. Also, the above drying and reduction may be performed in the same step. By repeating the above steps multiple times, the amount of the iron compound 111 adhering to the porous material 100 can be increased.

The reduction temperature of the iron compound 111 in step S113 should be at least 500° C. or higher. The range of the reduction temperature is, for example, 500°C to 1200°C, 500°C to 1000°C, 500°C to 900°C, or 700°C to 900°C. The reducing gas used for the reduction treatment of the iron compound 111 is carbon monoxide gas, hydrogen gas, hydrogen sulfide gas, sulfur dioxide gas, or hydrocarbon gas. The advantage of introducing these gases from the outside is that the yield of the adsorbent after reduction is higher than in the case where the carbon, oxygen, sulfur, hydrogen, etc. adhering to the porous material 100 react by heating and generate reducing gas. It is also one of the effects of the present invention that it increases. Alternatively, a reducing gas such as carbon monoxide and hydrogen may be mixed. Furthermore, since many reducing gases are difficult to handle from the viewpoint of explosiveness and combustibility, they may be diluted with an inert gas. For example, it can be diluted with nitrogen gas so that the carbon monoxide concentration is 1% or more and 20% or less (that is, the nitrogen concentration is 99% or less and 80% or more). The reduction time is 1 minute or more and 10 hours or less, and 10 minutes or more and 2 hours or less. The reduction may be of either a batch type or a continuous type, and a tube furnace or a box furnace may be appropriately used as long as it has a structure that allows heating and the introduction of a reducing gas (which may be mixed with an inert gas). can. When carbon monoxide gas is used as the reducing gas, the reduction temperature should be at least 500° C. or higher. The range of the reduction temperature in this case can be, for example, 500° C. to 1200° C., 500° C. to 1000° C., 500° C. to 900° C., or 700° C. to 900° C. Moreover, when hydrogen gas is used as the reducing gas, the reduction temperature should be at least 100° C. or higher. The range of the reduction temperature in this case can be, for example, 100° C. or higher and 1200° C. or lower, 100° C. or higher and 900° C. or lower, or 700° C. or higher and 900° C. or lower.

When reducing the iron compound 111, in addition to the reducing gas, carbon dioxide gas, oxygen gas, and water vapor are added to activate, thereby increasing fine pores in the porous material 100 at the same time as the reduction (activating carbonization). )be able to. By subjecting the porous material 100 to active carbonization, the surface area of the porous material 100 can be increased.

In step S113, when carbon, oxygen, sulfur, hydrogen, etc. adhering to the porous material 100 react by heating to generate a reducing gas, the gas is used to cover the inside of the pores of the porous material 100 and the surface thereof. Reduction treatment of the attached iron compound 111 may be performed. In this case, an inert gas, rare gas, or the like may be introduced into the heating device.

In this embodiment, after the mesopores 210 and micropores 220 are formed in the porous material 100, the iron-containing solution 120 is impregnated into the pores of the porous material 100, dried, and the iron compound 111 was able to realize the adsorbent 10 as described above.

Moreover, in the present embodiment, since the reduction is performed by a heat treatment different from the carbonization, the conditions suitable for the reduction can be appropriately selected. For example, the carbonization and reduction treatments can be performed in different apparatuses. Alternatively, the carbonization temperature and the reduction temperature can be treated at different temperatures and times. Alternatively, carbonization and reduction treatment can be performed in different atmospheres.

If the porous material 100 is a carbide, the carbide has high electrical conductivity, so electrons are rapidly exchanged between the carbide and the crystal grains of zero-valent iron adhering to the pores. Therefore, when a carbide containing crystal particles of zero-valent iron is placed in water, the zero-valent metallic iron is rapidly ionized on the surface of the porous body to produce hydroxides such as iron oxyhydroxide (FeOOH), It can react with phosphate ions present in water to form iron phosphate, which can be adsorbed and fixed on carbide. Similar to the above, phosphorus can be efficiently adsorbed by using a conductive material as the porous material 100 .

Although one embodiment of the present invention has been described above with reference to the drawings, the present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the scope of the present invention. For example, based on the adsorbent of the present embodiment, additions, deletions, or design changes made by those skilled in the art as appropriate are also included in the scope of the present invention as long as they have the gist of the present invention. Furthermore, the embodiments described above can be appropriately combined as long as there is no contradiction, and technical matters common to each embodiment are included in each embodiment without explicit description.

Even if there are other effects that are different from the effects brought about by the aspects of each embodiment described above, those that are obvious from the description of this specification or those that can be easily predicted by those skilled in the art are of course It is understood that it is provided by the present invention.

10: Adsorbent 100: Porous material 110: Iron ions 111: Iron compound 120: Solution 130: Bubbles 200: Macropores 201: Inner wall 210: Mesopores 220: Micropores 600: Metallic iron 601: Frame 610: Linear body 800: Iron oxide 801: Frame 810: Iron oxide 811: Frame 900: Iron sulfide 901: Frame

Claims (6)

a porous material;
Metallic iron inside the pores of the porous material;
iron oxide and iron sulfide on the surface of the porous material;
Adsorbent that adsorbs phosphorus and arsenic . The adsorbent according to claim 1, wherein said metallic iron is fibrous. The adsorbent according to claim 2, wherein said fibrous metallic iron includes a plurality of linear bodies. 4. The adsorbent according to any one of claims 1 to 3, wherein said metallic iron is crystalline. The adsorbent according to claim 1 or 2, wherein said iron oxide or said iron sulfide is granular. immersing the porous material in an iron sulfate solution,
After the immersion, a reduction treatment is performed by heat-treating the porous material in a reducing gas atmosphere,
During the reduction treatment, in addition to the reducing gas, carbon dioxide gas, oxygen gas, and water vapor are added for activation,
The method for producing an adsorbent that adsorbs phosphorus and arsenic, wherein the reducing gas is carbon monoxide gas, hydrogen gas, hydrogen sulfide gas, sulfur dioxide gas, or hydrocarbon gas.

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