JP7177840B2 - Method for producing adsorbent that adsorbs phosphorus or arsenic - Google Patents

Description

The present invention relates to a method for manufacturing an adsorbent. In particular, the present invention relates to a method of making an adsorbent that adsorbs phosphorus and arsenic.

In order to reduce the amount of carbon dioxide in the atmosphere, techniques for artificially collecting and storing carbon dioxide in the ground are known. For example, biomass such as trees and agricultural products can be used to absorb carbon dioxide in the atmosphere and fix the carbon dioxide as organic carbon. However, since such biomass is organic matter, even if it is stored in the ground as it is, it will putrefy or decompose, and carbon dioxide will be re-released 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. In this way, by burying the carbonized biomass in agricultural land or the like, carbon dioxide can be converted into carbon and isolated and stored underground. In other words, burying carbonized biomass in the ground leads to a reduction in the amount 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 Literature 1 describes a phosphorus recovery material using a calcium-supporting carbide. By adsorbing phosphorus using such a phosphorus recovery material, it is possible to suppress water pollution caused by discharge of phosphorus into natural waters. Furthermore, when the phosphorus recovery material that adsorbs phosphorus is buried in farmland, the phosphorus adsorbed to the phosphorus recovery material is dissolved by the organic acid released from the roots of the crops. That is, since this phosphorus functions as a fertilizer for agricultural crops, it is possible to improve the yield of agricultural land in which the phosphorus recovery material is buried, or to grow good agricultural crops.

In this way, it is possible not only to improve the quality of soil, but also to apply charcoal that can suppress environmental pollution by adsorbing a certain toxic substance, or that toxic substance to other uses. Demand for carbides that can be used is increasing.

JP-A-2007-75706

However, in the phosphorus recovery material of Patent Document 1, it is necessary to use a material containing a large amount of silicon such as rice husk or diatomaceous earth. When using silicon-rich materials, there is a limit to the amount of phosphorus recovery material that can be produced. Also, there is a limit to the amount of material that can be adsorbed, such as phosphorus.

One embodiment of the present invention has been made in view of the above problem, and an object thereof is to provide a method for manufacturing an adsorbent that can manufacture an adsorbent using various materials.

A method for producing an adsorbent according to one embodiment of the present invention includes carbonizing an organic substance to form a carbide, infiltrating a solution containing iron into the pores of the carbide, and impregnating the solution containing iron. and drying the charcoal.

The solution may contain iron ions.

The solution may be colloidal comprising particles comprising iron hydroxide.

The solution may contain heme iron.

An alkaline solution may be impregnated into the pores of the dried charcoal to form iron hydroxide particles, the alkaline solution may be discharged out of the pores of the charcoal, and the charcoal may be dried.

A method for producing an adsorbent according to one embodiment of the present invention includes carbonizing an organic substance to form a carbide, and injecting a solution containing iron ions and anions paired with the iron ions into the pores of the carbide. An alkaline solution is soaked into the pores of the carbide soaked with the solution to generate iron hydroxide particles, the anions and the alkaline solution are discharged out of the pores, and the carbide is dried. .

The iron hydroxide particles may be reduced.

The carbide impregnated with the iron-containing solution may be dried to allow an iron compound to adhere to the carbide, thereby reducing the iron contained in the iron compound.

The pressure may be reduced while the carbide is immersed in the solution.

The reduction may be performed using a gas containing hydrogen, carbon monoxide, or hydrocarbons.

The reduction may be performed at a temperature of 500° C. or higher using a gas containing carbon monoxide.

The reduction may be performed at a temperature of 100° C. or higher using a gas containing hydrogen.

According to one embodiment of the present invention, it is possible to provide a method for manufacturing an adsorbent that can manufacture an adsorbent using various materials.

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. It is a figure which shows the manufacturing method of the adsorbent which concerns on one Embodiment of this invention. It is a figure which shows the manufacturing method of the adsorbent which concerns on one Embodiment of this invention. It is a figure which shows the manufacturing method 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. FIG. 2 is a conceptual diagram showing a specific method for producing iron hydroxide in the adsorbent according to one embodiment of the present invention. It is a flow chart which shows a manufacturing method of adsorbent concerning one embodiment of the present invention. FIG. 2 is a conceptual diagram showing a specific method for producing iron hydroxide in the adsorbent according to one embodiment of the present invention. 1 is a flow chart showing a method for producing an iron-containing solution according to one embodiment of the present invention. FIG. 4 is a diagram illustrating a method of decompressing a porous material immersed in a solution in a method of manufacturing an adsorbent according to an embodiment of the present invention;

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 letters after the same reference numerals, and repeated description thereof will be omitted.

In the following embodiments, as a porous material used as an adsorbent, a carbonized material obtained by carbonizing wood will be exemplified, but it is not limited to this configuration. 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.

<First embodiment>
[Method for manufacturing adsorbent 10]
An adsorbent 10 according to the first embodiment and a method for manufacturing the adsorbent 10 will be described with reference to FIGS. 1 to 5. FIG. In this embodiment, as the porous material 100 used in the adsorbent 10 (see FIG. 5), a carbide obtained by carbonizing an organic substance is used, and as a method for introducing metal particles into the pores of the carbide, a solution containing iron is used. A configuration in which zerovalent iron particles are arranged in the pores of the carbide by using a method of immersing the carbide in the carbide and reducing the iron compound adhering to the pores of the carbide will be described.

FIG. 1 is a flow chart showing a method for manufacturing an adsorbent according to one embodiment of the present invention. FIG. 2 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. 3 to 5 are diagrams respectively showing a method for manufacturing an adsorbent according to one embodiment of the present invention.

As shown in FIG. 1, organic matter is carbonized in step S101. In this embodiment, wood is used as the organic matter. 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. Continuing to heat at a higher temperature further reduces oxygen and hydrogen in the organic matter, 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. 2, the porous material 100 has macropores 200 , 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 approximately 50 nm to 40 μm. The size of the mesopores 210 is approximately 2 nm to 50 nm. The size of the micropores 220 is approximately 0.5 nm to 2 nm or less.

As shown in FIG. 1, 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 is 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 ), ferric nitrate aqueous solution (Fe( _NO3 ) ₃ ), ferrous sulfate aqueous solution ( _FeSO4 ), ferric sulfate aqueous solution (Fe( _SO4 ) ₃ ), or polyferric sulfate solution ([ Fe ₂ (OH) _n (SO ₄ ) _3−n/2 ] _m for 0<n≦2, m=f(n)) 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. FIG. 3 shows the state at this time. As shown in FIG. 3, when the solution 120 is supplied to the porous material 100, the solution 120 penetrates into the pores of the porous material 100 (macropores 200, mesopores 210, and micropores 220 (see FIG. 2)). to (permeate) Along with this, the iron ions 110 in the solution 120 also enter the pores of the porous material 100 . That is, by immersing the porous material 100 in the solution 120 , the iron ions 110 are permeated into the pores of the porous material 100 .

Here, the mesopores 210 and the micropores 220 are much smaller in size than the macropores 200 and their tips are dead ends inside the porous material 100 . Therefore, when the solution 120 permeates into the pores of the porous material 100, air bubbles 130 may be generated at the tips of the micropores 220, for example. In the example of FIG. 3 , the bubble 130 is generated only at the tip of the micropore 220 , but the bubble 130 may extend to the mesopore 210 or to the macropore 200 . Since the solution 120 cannot penetrate into the region where the air bubbles 130 exist, the iron ions 110 cannot be supplied to this region.

In order to eliminate such a phenomenon, in step S107 of FIG. 1, the atmosphere in which the porous material 100 is immersed in the solution 120 is decompressed. FIG. 4 shows the state at this time. As shown in FIG. 4, when the atmosphere in which the solution 120 is supplied to the porous material 100 is decompressed, the air bubbles 130 existing at the tips of the micropores 220 as shown in FIG. diffuse out of the pores. This process is sometimes called degassing. As shown in FIG. 4, when the bubbles 130 diffuse out of the hole, the solution 120 can enter the position where the bubbles 130 existed in FIG. In an example, the micropores 220) can be supplied with iron ions 110. FIG. In the case where bubbles do not occur inside the holes as described above, or even if bubbles occur inside the holes, if the presence of the bubbles does not adversely affect the characteristics of the adsorbent 10, This step S107 and the next step S109 may be omitted.

In step S109, the atmosphere pressure-reduced in step S107 is returned to the atmospheric pressure, the porous material 100 is removed from the solution 120, and the porous material 100 impregnated with the solution 120 is dried in step S111. This drying removes the liquid contained in the solution 120 . 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.

FIG. 5 shows the dried state of the porous material 100 after being immersed in the solution 120 . As shown in FIG. 5, by removing the solvent contained in the solution 120, the iron ions 110 contained in the solution 120 are precipitated and the iron compound 111 is formed. This iron compound 111 adheres to the inside of the pores of the porous material 100 and to the surface thereof. Specifically, the iron compound 111 adheres to the inner wall of at least one of the macropores 200 , mesopores 210 and micropores 220 . Note that in FIG. 5, the iron compound 111 adheres to the inner walls of all these holes. In steps S105-S109, the solution 120 can also be supplied to the mesopores 210 and micropores 220, so that the iron compound 111 can adhere to the inner walls of these pores in step S111.

In step S113 of FIG. 1, the reduction treatment of the iron compound 111 adhering in the pores of the porous material 100 and on 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.

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 scraps, chip scraps, 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 matter in step S101 is 400° C. or higher and 1200° C. or lower, 500° C. or higher and 1100° C. or lower, 600° C. or higher and 1000° C. or lower, or 700° C. or higher and 900° C. or lower. 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, a low vacuum state of -101200 Pa or more and -1300 Pa or less, a medium vacuum state of -101299.9 Pa or more and -101200 Pa or less, and a gauge pressure of -101299.99999 Pa or more at a gauge pressure with the atmospheric pressure as zero. It can be carried out in a high vacuum state of −101299.9 Pa or an ultra-high vacuum state of −101299.99999 Pa or less. 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 substances 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 5 wt % or more and 15 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 5 minutes to 1 hour. When the pressure is reduced after the carbide is immersed in a pressure vessel, the gauge pressure is usually -0.101 MPa or more and -0.02 MPa or less, -0.101 MPa or more and -0.04 MPa or less, or -0.101 MPa. Above -0.08 MPa or less. In this case, the reduced-pressure immersion time may be shorter than usual, and may be appropriately selected from 1 second or more and 1 hour or less, 10 seconds or more and 10 minutes or less, or 30 seconds or more and 5 minutes or less after reaching a predetermined gauge pressure. good.

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 in 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.

When the pressure is reduced as described above, the bubbles 130 in the porous material 100 become larger, the buoyancy of the porous material 100 increases, and the porous material 100 may float above the liquid surface. In order to suppress this phenomenon, a mesh-like floating prevention plate smaller than the porous material 100 may be installed in the container containing the solution 120 . If the porous material 100 floats above the liquid surface, the replacement efficiency between the bubbles 130 and the solution 120 on the liquid surface becomes poor. You may end up inside. However, by installing the anti-floating plate as described above, such a phenomenon can be suppressed.

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 process 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. 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 concentration of carbon monoxide is 1% to 20% (that is, the concentration of nitrogen is 99% to 80%). 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.

Conventionally, when an iron compound is formed inside a carbide, a dried organic substance before carbonization is immersed in a solution in which the iron compound is dissolved, dried, and then carbonized. Since the above-mentioned macropores 200 are pores caused by tracheid holes in wood, it is considered that reduced zerovalent iron crystals are deposited on the inner walls of the macropores 200 . In addition, when a raw organic matter such as raw wood before drying is immersed in a solution in which the iron compound is dissolved, the iron compound can be immersed into the organic matter due to diffusion and penetration, but the carbonized material after carbonization There is a possibility that zero-valent iron crystals are not sufficiently deposited on the pore surfaces of the

In contrast, in the present embodiment, after the mesopores 210 and micropores 220 are formed in the porous material 100, the solution 120 containing iron is soaked into the pores of the porous material 100 and dried. An iron compound 111 can be deposited on the inner walls of these pores and, after reduction, zerovalent iron crystals can be deposited on the inner walls of these pores.

Conventionally, in the heat treatment for carbonizing organic matter, carbon monoxide and hydrogen generated during carbonization have been used to reduce the iron compounds. Therefore, the conditions for carbonization and the conditions for reduction treatment could not be controlled separately. For example, it has been difficult to adjust the amount of reducing gas required to reduce iron compounds.

On the other hand, 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. Here, when the reduction treatment of iron is performed in an inert gas atmosphere or an oxygen-free atmosphere, the counter ion of the metal compound in the carbide reacts with the carbon constituting the carbide by heating, and carbon monoxide or hydrogen is produced. generated. For example, in the case of carbide containing iron sulfate, sulfurous acid gas produced by heating reacts with carbon in the carbide to produce carbon monoxide and sulfur dioxide. Alternatively, oxygen in the carbide reacts with carbon forming the carbide to produce carbon monoxide. Alternatively, the hydrogen contained in the carbide is thermally decomposed to produce methane and hydrogen. The carbon monoxide, methane, or hydrogen is consumed by iron reduction. Therefore, it is considered that the content of carbon and hydrogen in the carbide decreases, and the yield of the carbide used as an adsorbent decreases. On the other hand, when the reduction treatment of iron is performed in a reducing gas atmosphere, the reducing gas used for reducing the iron is supplied from the outside, so that the metal counterions or oxygen and hydrogen of the metal compound in the carbide constitute the carbide. Reaction with carbon is suppressed. Therefore, it is considered that the decrease in the carbon content of the carbide used as the adsorbent is suppressed.

In this embodiment, the porous material 100 is made of carbide obtained by carbonizing an organic substance. However, the porous material 100 may be made of a material other than carbide. Moreover, although the configuration for obtaining the porous material 100 by carbonizing wood as an organic substance has been exemplified, organic substances other than wood may be carbonized. Further, in step S103, the solution 120 is a ferrous sulfate aqueous solution (FeSO ₄ ), a ferric sulfate aqueous solution (Fe(SO ₄ ) ₃ ), or a polyferric sulfate solution ([Fe ₂ (OH) _n ( SO ₄ ) _3−n/2 ] _m , where 0<n≦2, m=f(n)), the adsorbent 10 obtained by the reduction treatment in step S113 contains iron oxide and/or iron sulfide. may be attached. Iron oxide and/or iron sulfide may be present on the surface of the carbide or within the pores (macropores 200, mesopores 210, and/or micropores 220).

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 .

<Second embodiment>
[Manufacturing method of adsorbent 10A]
A method for manufacturing the adsorbent 10A according to the second embodiment will be described with reference to FIG. The manufacturing method of the adsorbent 10A is similar to the manufacturing method of the adsorbent 10 according to the first embodiment shown in FIG. is further immersed in an alkaline solution, which is different from the manufacturing method of the adsorbent 10 of the first embodiment. In the following explanation of FIG. 6, the explanation of the parts common to FIG. 1 will be omitted, and mainly the points different from FIG. 1 will be explained. Note that the configuration of the adsorbent 10A according to this embodiment is the same as the configuration of the adsorbent 10 according to the first embodiment, so illustration thereof is omitted here. In the following description, in the configuration of the adsorbent 10A, the same configuration as the adsorbent 10 is given the same reference numerals as those used in the adsorbent 10, followed by the alphabet "A", and the description thereof is omitted. .

As shown in FIG. 6, after drying the porous material 100A impregnated with the solution 120A in step S111A, the porous material 100A is immersed in an alkaline solution in step S115A. At this time, the iron compound 111A adheres to the inner walls of the pores of the porous material 100A as in FIG. Therefore, when the porous material 100A is immersed in an alkaline solution, the alkaline solution permeates into the pores of the porous material 100A, and comes into contact with the iron compound 111A, at least part of the iron compound 111A is hydroxylated. Thus, iron hydroxide is produced on the inner walls of the pores of the porous material 100A.

After the generation of iron hydroxide, the porous material 100A is washed with water (step S120A). This water washing can remove the alkali metal ions generated in the pores of the porous material 100A, the anions bound to iron in the iron compound, and the alkaline solution remaining in the pores. Here, since the iron hydroxide existing on the inner walls of the pores of the porous material 100A has a low solubility, it is difficult to discharge out of the porous material 100A even after the above water washing. In addition, if the inside of the porous material 100A is biased towards alkalinity, the adsorption power of, for example, phosphorus is weakened. By removing the solution, it is possible to prevent the inside of the porous material 100A from becoming alkaline. Note that the water washing in step S120A may be omitted. Also, washing with water may be performed after drying in step S121A.

In order to allow the alkaline solution to permeate into the mesopores 210A and the micropores 220A, degassing is performed in the same manner as in step S107A, thereby hydroxylating the iron compound 111A present in the pores. A porous material 100A having iron hydroxide adhered to the inner wall can be obtained (steps S117A, S119A, S120A, S121A). After washing the dried porous material 100A in step S121A with water, reduction treatment in step S113A is performed.

Note that a solution of sodium hydroxide (NaOH), potassium hydroxide (KOH), or the like can be used as the alkaline solution used in step S115A.

The above steps S115A to S121A may be repeated multiple times. Also, the steps S117A and S119A described above may be repeated multiple times. Steps S117A and S119A may be omitted.

As described above, according to the method for manufacturing the adsorbent 10A according to the present embodiment, the reduction treatment can be performed while the iron compound 111A is hydroxylated. That is, the gas generated by the reduction treatment is harmless water vapor.

Here, a more specific example of this embodiment will be described with reference to FIG. Here, the case where the iron chloride solution 150A is used as the solution 120A and the sodium hydroxide solution 140A is used as the alkaline solution will be described. FIG. 7 is a conceptual diagram showing a specific method for producing iron hydroxide in the adsorbent according to one embodiment of the present invention. FIG. 7 shows the inner walls 101A of the pores (macropores 200A, mesopores 210A, and micropores 220A) of the porous material 100A, and illustrates phenomena in the regions surrounded by the inner walls 101A.

As shown in FIG. 7A, in the iron chloride solution 150A, anions (chloride ions 153A) paired with the iron ions 151A are present in addition to the iron ions 151A. The iron chloride solution 150A is impregnated into the porous material 100A, and the solvent contained in the iron chloride solution 150A is removed by drying, thereby depositing solid iron chloride 155A on the inner walls 101A of the pores of the porous material 100A. ((B) in FIG. 7).

When the sodium hydroxide solution 140A is impregnated into the porous material 100A in which the iron chloride 155A is deposited on the inner wall 101A, the hydroxide ions in the sodium hydroxide solution react with the iron chloride in the porous material 100A. Iron hydroxide 141A, chloride ions 143A, and sodium ions 145A in the sodium hydroxide solution are produced (FIG. 7C). That is, when the sodium hydroxide solution 140A comes into contact with the iron chloride 155A deposited on the inner wall 101A, the hydroxide ions of the sodium hydroxide solution 155A are replaced with the chlorine of the iron chloride 155A by a chemical reaction, and the iron hydroxide 141A and the chloride A material ion 143A is produced. Since the iron hydroxide 141A has low solubility in water, it precipitates as a solid on the inner wall 101A and is retained within the porous material 100A. On the other hand, since sodium chloride is highly soluble in water, it exists as chloride ions 143A and sodium ions 145A, and can be removed from the pores of the porous material 100A by washing with water in step S120A, for example ((D )). Furthermore, by washing with water, the excess sodium hydroxide solution 140A that has not been used for the reaction in the pores can also be removed from the porous material 100A ((D) in FIG. 7). That is, among the iron compounds (iron chloride) in the iron chloride solution 150A, the substance (chlorine) bound to iron is anionized and discharged out of the porous material 100A together with the sodium hydroxide solution 140A.

In other cases, similarly to the above, in the pores of the porous material 100A, iron hydroxide (solid) produced by a chemical reaction, anions and alkali metal ions ( liquid), as well as excess alkaline solution (liquid), which can be removed by washing with water except iron hydroxide. As a result, the anion-derived element (“chlorine” in the above example) in the solution 120A can be removed before reduction, and the amount of acid gas generated during the reduction treatment can be greatly suppressed. If hydroxide is not generated in the manufacturing process of the adsorbent, hydrogen chloride gas is generated if the solution 120A contains iron chloride, and nitric acid is generated if the solution 120A contains iron nitrate. Gas is generated, and if the solution 120A is a solution containing iron sulfate, acid gas such as sulfuric acid gas is generated. Therefore, a scrubber is required to remove the acid gas. On the other hand, as in the present embodiment, by generating hydroxide in the manufacturing process of the adsorbent, there is no need to provide a scrubber for removing the above gases, and the adsorbent manufacturing apparatus can be simplified. is possible.

<Modification of Second Embodiment>
A modification of the second embodiment will be described with reference to FIGS. 8 and 9. FIG. FIG. 8 is a flow chart showing a method for manufacturing an adsorbent according to one embodiment of the present invention. FIG. 9 is a conceptual diagram showing a specific method for producing iron hydroxide in the adsorbent according to one embodiment of the present invention.

The process shown in FIG. 8 is a process in which steps S107A to S111A are omitted from FIG. That is, after the porous material 100A is immersed in the solution 120A, it is immersed in the alkaline solution without drying. FIG. 6 shows a manufacturing method in which the iron compound 111A is chemically reacted in a state where the iron compound 111A is deposited on the inner wall 101A of the pores of the porous material 100A to generate the iron hydroxide 141A. Iron ions 110A in the solution 120A and hydroxide ions 147A in the alkaline solution are chemically reacted to precipitate iron hydroxide 141A on the inner wall 101A.

Here, a more specific example of the modified example of this embodiment will be described with reference to FIG. 9 . Since FIG. 9 is similar to FIG. 7, descriptions of features in FIG. 9 that are the same as in FIG. 7 will be omitted. In the following description, the iron chloride solution 150A is used as the solution 120A, and the sodium hydroxide solution 140A is used as the alkaline solution.

As shown in FIG. 9A, in the porous material 100A that has not been dried after being immersed in the iron chloride solution 150A, the iron chloride solution 150A contains iron ions 151A and chloride ions 153A. Existing. When the sodium hydroxide solution 140A is supplied to the porous material 100A in this state, the sodium hydroxide solution 140A enters into the pores of the porous material 100A by diffusion permeation (FIG. 9B). Incidentally, as shown in FIG. 9B, sodium ions 145A and hydroxide ions 147A are present in the sodium hydroxide solution 140A.

As the sodium hydroxide solution 140A enters the pores of the porous material 100A, iron ions 151A, chloride ions 153A, sodium ions 145A, and hydroxide ions 147A are present in the pores of the porous material 100A. ((C) in FIG. 9). Although FIG. 9C illustrates a configuration in which the inside of the pores of the porous material 100A is replaced with the sodium hydroxide solution 140A instead of the iron chloride solution 150A, these solutions may be mixed. A chemical reaction between iron ions 151A and hydroxide ions 147A in the pores of the porous material 100A generates iron hydroxide 141A, which precipitates on the inner walls 101A of the pores in the porous material 100A (( D)). By washing with water in this state, the chloride ions 153A other than the iron hydroxide 141A, the sodium ions 145A, and the sodium hydroxide solution 140A can be removed from the holes ((D) in FIG. 9).

According to the modification of the second embodiment, it is not necessary to dry the porous material 100A after immersing it in the iron chloride solution 150A, so the manufacturing process can be simplified.

In the modified example of the second embodiment, the manufacturing method of immersing the porous material 100A in the alkaline solution was exemplified. A method of supplying an alkaline solution to the surface of the material 100A may be employed. For example, an alkaline solution may be sprayed onto the surface of the porous material 100A.

<Third embodiment>
[Manufacturing method of adsorbent 10B]
A method for manufacturing the adsorbent 10B according to the third embodiment will be described with reference to FIG. The manufacturing method of the adsorbent 10B is similar to the manufacturing method of the adsorbent 10 according to the first embodiment shown in FIG. It is different from the manufacturing method of the adsorbent 10 of the first embodiment in that it is colloidal.

FIG. 10 is a flow chart showing a method for producing an iron-containing solution according to one embodiment of the present invention. As shown in FIG. 10, the solution 120B used in this embodiment is prepared by steps S131B-S135 as detailed below. Note that the following steps S131B to S135B are processes corresponding to step S103 shown in FIG.

First, in step S131B, the iron solution described in step S101 of FIG. 1 is prepared. Subsequently, in step S133B, the alkaline solution described in step S115A of FIG. 6 is added to this iron solution. When the alkaline solution is added to the iron solution, the iron solution becomes colloidal containing particles of iron hydroxide. Specifically, the iron aqueous solutions exemplified above (ferrous chloride aqueous solution, ferric chloride aqueous solution, ferrous nitrate aqueous solution, ferric nitrate aqueous solution, ferrous sulfate aqueous solution, or ferric sulfate aqueous solution) to which an alkaline solution (sodium hydroxide solution, potassium hydroxide solution) is added, the aqueous iron solution becomes colloidal containing particles of iron hydroxide. A solution in this state can also be called a colloidal solution. Subsequently, in step S135B, a dispersant as exemplified in the first embodiment is added.

This colloidal solution contains iron hydroxide particles with a size of 1 nm or more and 100 nm or less. Therefore, by infiltrating the colloidal solution into the mesopores 210B and the micropores 220B, the iron hydroxide particles can enter these pores.

The porous material 100B is immersed in the colloidal solution, washed with water, and then dried, or immersed, dried, and then washed with water to adhere iron hydroxide particles to the inner walls of the pores of the porous material 100B. , unreacted iron ions, anions paired with the iron ions in the iron solution, and alkali metal ions can be removed from the pores of the porous material 100B. By subjecting the iron hydroxide particles to a reduction treatment, it is possible to obtain zero-valent iron adhering to the inner walls of the pores of the porous material 100B.

Even if the particles in the colloidal solution can be sufficiently dispersed without using a dispersant, or even if the particles are insufficiently dispersed in the colloidal solution, the characteristics of the adsorbent 10B are not adversely affected. If so, the step of adding the dispersant (step S135B) may be omitted.

As described above, according to the method for manufacturing the adsorbent 10B according to the present embodiment, zerovalent iron can be obtained by subjecting the iron hydroxide particles to the reduction treatment. Even when it is used, solid iron hydroxide is formed inside the pores of the porous material, and sodium chloride is removed outside the pores, so the amount of acid gas generated during the reduction treatment is suppressed. can do.

An example of a method of depressurizing the porous material 100 (or 100A, 100B) immersed in the solution 120 (or 120A, 120B) in the above embodiment will be described with reference to FIG. FIG. 11 is a diagram illustrating a method of decompressing a porous material immersed in a solution in a method of manufacturing an adsorbent according to one embodiment of the present invention.

As shown in FIG. 11, the decompression container 400 has a container portion 401 and a lid portion 403 . The container part 401 has a shape capable of storing the solution 120 . The lid portion 403 is detachably provided on the upper portion of the container portion 401 . The lid portion 403 is provided with an exhaust port 405 and an air supply port 407 . The exhaust port 405 is connected to the first valve 410 . First valve 410 is connected to vacuum pump 430 . Air inlet 407 is connected to second valve 420 . The second valve 420 is connected to a pipe 435 that supplies air or desired gas from the outside into the decompression vessel 400 . A vacuum pressure gauge 440 is also connected to the decompression container 400 . A vacuum pressure gauge 440 can measure the pressure inside the reduced pressure vessel 400 . Note that an aspirator may be used instead of the vacuum pump 430 .

Further, as shown in FIG. 11 , a solution 120 is supplied to the decompression container 400 and the porous material 100 is immersed in the solution 120 . A case 500 containing the porous material 100 is submerged in the solution 120 . The case 500 has a shape surrounding its internal space, and is submerged in the solution 120 with the porous material 100 stored in the internal space. In other words, the case 500 prevents the porous material 100 from rising above the liquid surface of the solution 120 , and allows the porous material 100 to be lifted when the case 500 is removed from the decompression container 400 .

The case 500 is provided with an opening of a size through which the solution 120 can pass and a size through which the porous material 100 cannot pass. The size of the opening is, for example, 0.1 mm or more and 50 mm or less. As the case 500, for example, a net-like cage made of metal such as stainless steel or resin such as hard plastic can be used. Although the configuration in which the case 500 surrounds the porous material 100 on the top, bottom, left, and right is illustrated here, the configuration is not limited to this. For example, the case 500 may have a shape in which the upper part of the porous material 100 is covered so as to prevent the porous material 100 from floating upward, and the lower part is removed. Alternatively, the case 500 is provided above the porous material 100 and below the porous material 100 so that the porous material 100 can be lifted when the case 500 is removed from the decompression container 400. good too.

By operating the vacuum pump 430 with the first valve 410 open and the second valve 420 closed, the inside of the decompression container 400 is decompressed. After that, by supplying air or a desired gas to the pipe 435 with the first valve 410 closed and the second valve 420 open, the inside of the decompression container 400 can be returned to the atmospheric pressure.

After the above processing is completed, the lid portion 403 is opened and the case 500 is taken out together with the porous material 100 . At this time, since the opening is provided in a part of the case 500 corresponding to the lower portion of the porous material 100, the porous material 100 can be taken out while dropping the excessive solution 120 into the pressure-reduced container 400. .

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 101A: Inner wall 110: Iron ion 111: Iron compound 120: Solution 130: Bubbles 140A: Sodium hydroxide solution 141A: Iron hydroxide 143A: Chloride ion, 145A: sodium ion, 147A: hydroxide ion, 150A: iron chloride solution, 151A: iron ion, 153A: chloride ion, 155A: iron chloride, 200: macropore, 210: mesopore, 220: micropore 400: Decompression container 410: Container part 403: Lid part 405: Exhaust port 407: Air supply port 410: First valve 420: Second valve 430: Vacuum pump 435: Piping 440: Vacuum pressure gauge, 500: case

Claims (8)

carbonizing organic matter to form carbides,
impregnating a solution containing iron into the pores of the carbide;
drying the carbide impregnated with the iron-containing solution;
A method for producing an adsorbent that adsorbs phosphorus or arsenic, wherein the solution is colloidal containing particles containing iron hydroxide. carbonizing organic matter to form carbides,
impregnating a solution containing iron into the pores of the carbide;
drying the carbide impregnated with the iron-containing solution;
The method for producing an adsorbent that adsorbs phosphorus or arsenic, wherein the solution contains heme iron. generating iron hydroxide particles by infiltrating an alkaline solution into the pores of the dried carbide;
discharging the alkaline solution out of the pores of the carbide;
3. The method for producing an adsorbent according to claim 1, wherein the charcoal is dried. carbonizing organic matter to form carbides,
infiltrating the pores of the carbide with a solution containing iron ions and anions paired with the iron ions;
generating iron hydroxide particles by impregnating an alkaline solution into the pores of the carbide impregnated with the solution;
discharging the anions and the alkaline solution out of the pores;
drying the char;
A method for producing an adsorbent that adsorbs phosphorus or arsenic and that reduces the iron hydroxide particles. carbonizing organic matter to form carbides,
impregnating a solution containing iron into the pores of the carbide;
drying the carbide impregnated with the iron-containing solution;
generating iron hydroxide particles by infiltrating an alkaline solution into the pores of the dried carbide;
discharging the alkaline solution out of the pores of the carbide;
drying the char;
A method for producing an adsorbent that adsorbs phosphorus or arsenic and that reduces the iron hydroxide particles. The method for producing an adsorbent according to claim 4 or 5, wherein the reduction is performed using a gas containing hydrogen, carbon monoxide, or hydrocarbons. 6. The method for producing an adsorbent according to claim 4, wherein said reduction is performed at a temperature of 500[deg.] C. or higher using a gas containing carbon monoxide. 6. The method for producing an adsorbent according to claim 4, wherein said reduction is performed at a temperature of 100[deg.] C. or higher using a gas containing hydrogen.

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