JP7193067B2 - Phosphorus adsorbent and its manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a phosphorus adsorbent and its manufacturing method, and more particularly to a phosphorus adsorbent produced using incineration ash as a main raw material and its manufacturing method.

As prior art, a phosphorus adsorbent (also referred to as a phosphorus recovery material) produced from papermaking sludge or coal ash as a raw material and a method for producing the same are already known.

For example, Patent Document 1 below describes a phosphorus adsorbent derived from papermaking sludge and a method for producing the same. The phosphorus adsorbent described in Patent Document 1 is a phosphorus adsorbent derived from papermaking sludge containing an alkaline substance component and a carbon component. and an alkaline component coordinated to the pore surface.

This phosphorus adsorbent does not contain harmful substance components, and is produced by thermally decomposing papermaking sludge containing alkaline components and carbon components by indirect heating to obtain a porous adsorbent containing alkaline components and carbon components. obtained and produced by a phosphorus sorbent production facility.

This phosphorus adsorbent production facility comprises a drying furnace for drying raw papermaking sludge, crushing means for crushing the raw material dried in the drying furnace, and thermal decomposition of the raw material dried in the drying furnace. A pyrolysis furnace for obtaining charcoal of high quality, a pulverizing transfer means for pulverizing and recovering the charcoal obtained in this pyrolysis furnace, steam generated in the drying furnace and pyrolysis gas generated in the pyrolysis furnace are kept in a constant atmosphere and It consists of a gas combustion furnace that burns under a residence time (for example, a residence time of 2 seconds or more in an atmosphere of about 850° C.) and detoxifies it, and their incidental equipment.

According to this phosphorus adsorbent production facility, the papermaking sludge is dried and thermally decomposed by indirect heating from the outside in a reducing atmosphere, so even if the papermaking sludge contains harmful chlorine and sulfur, Also, these components can be effectively removed and can be reused as a safe and secure resource without remaining in the dried matter or charcoal. In addition, by adding and mixing an alkaline substance as a drug that reacts with the harmful substances generated by decomposition and deposition during heat processing of the adsorbent and replaces it with a harmless substance, the alkaline substance is reduced in the thermal decomposition process. is taken into the adsorbent, the adsorbent becomes even richer in alkaline components, and an improvement in the adsorption and recovery effect of phosphorus can be expected.

By the way, it is known that a cement-based phosphorus adsorbent reacts with phosphorus (phosphoric acid) to form calcium phosphate (hydroxyapatite) to adsorb phosphorus. However, calcium hydroxide is a strong alkali, and when it dissolves in water, it greatly increases the pH of the water quality of lakes and marshes. There is a problem.

A phosphorus recovery material that solves this problem is proposed in Patent Document 2 below. This phosphorus recovery material is composed of a mixture containing coal ash, gypsum, and an aqueous sodium hydroxide solution. According to this phosphorus recovery material, it is possible to suppress an increase in the alkalinity of the solution containing phosphorus, and to improve the phosphorus recovery performance.

Japanese Patent Application Laid-Open No. 2004-14003 Japanese Patent No. 5879171

The phosphorus adsorbent described in Patent Document 1 is made of porous carbide derived from papermaking sludge, and alkaline components are exposed on the surface and pore inner walls of this carbide, so in a solution containing phosphorus can be contacted and reacted with phosphorus to efficiently recover the phosphorus component.

However, this porous charcoal is produced by a drying furnace that dries papermaking sludge, a pyrolysis furnace that thermally decomposes raw materials dried in the drying furnace to obtain porous charcoal, and water vapor generated in the drying furnace. And it must be produced in a special phosphorus adsorbent production facility consisting of a gas combustion furnace that burns and detoxifies the pyrolysis gas generated in the pyrolysis furnace, and these incidental equipment. For this reason, this production facility requires various furnaces, that is, furnaces such as drying furnaces, pyrolysis furnaces and gas combustion furnaces, and ancillary equipment such as crushing and conveying means incidental thereto. The production facility, that is, the equipment and devices that make up this facility, are special, complicated, and expensive, requiring a large amount of capital investment. must supply and burn large amounts of petroleum fuel to various furnaces. As a result, the initial cost for equipment investment and the running cost during operation rise, and these costs are passed on to the product, that is, the phosphorus adsorbent, which makes it expensive, and there is a problem in commercial profitability.

In addition, this phosphorus adsorbent cannot increase the amount of the component that adsorbs phosphorus, and the carbides are formed in the shape of grains, so they cannot be formed into arbitrary shapes. The specific surface area of the body is small. As a result, the amount of phosphorus adsorbed cannot be increased, so the amount of phosphorus adsorbed is small, and the shape is limited, so the usage pattern is limited. There is also a problem in using the adsorbed/recovered phosphorus directly as a fertilizer.

In addition, the phosphorus recovery material described in Patent Document 2 cannot increase the amount of the component that adsorbs phosphorus, and the adsorbed and recovered phosphorus cannot be directly used as fertilizer. In addition, there is a problem that gypsum and an aqueous sodium hydroxide solution must be mixed in order to prevent the phosphorus-containing solution from increasing in alkalinity.

Since the conventional technology has many problems, the present inventors have found that as a method or means for solving these problems, if the phosphorus adsorbent to be produced is composed of a foamed hydrothermally solidified material instead of a carbide, Without using expensive phosphorus adsorbent production equipment, the initial cost associated with equipment investment and running cost during operation can be significantly reduced, resulting in a significant reduction in price, and moreover, when producing a foamed hydrothermally solidified product. In addition, the amount of the component that contributes to phosphorus adsorption can be increased, and the amount of adsorption increases, and the adsorbed and recovered phosphorus can be used directly as fertilizer. The present inventors have completed the present invention based on the idea that it is possible to suppress the increase in .

That is, the object of the present invention is to increase the phosphorus adsorption capacity by increasing the amount of components contributing to phosphorus adsorption, increasing the specific surface area, and synergizing the easy particle size adjustment, compared to the phosphorus adsorbents made of conventional carbides. It is an object of the present invention to provide a phosphorus adsorbent which is inexpensive and commercially profitable. Another object of the present invention is to provide a phosphorus adsorbent that stabilizes the pH within the range of the reference value, reduces phosphorus leaching due to rainfall, and retains the phosphorus in a form that can be used by plants. Further, another object of the present invention is to provide a phosphorus adsorbent which can use the adsorbed and recovered phosphorus as it is as a fertilizer and which can be desorbed with a dilute acid solution.

Furthermore, another object of the present invention is to eliminate the need for expensive generation equipment and reduce the running cost of operating the generation equipment, compared to the conventional carbonized phosphorus adsorbent generation equipment, and to reduce the cost. To provide a method for producing a phosphorus adsorbent having a high phosphorus adsorption capacity.

In order to achieve the above object, the phosphorus adsorbent of the first aspect of the present invention contains, as a main raw material, cement containing calcium in an amount of 5 to 25% with respect to 100% by mass of incinerated ash containing aluminum. It comprises a foamed hydrothermally solidified body produced by adding not more than mass %, the foamed hydrothermally solidified body contains calcium silicate hydrate composed of an aggregate of needle-like crystals, and the foamed hydrothermally solidified The body has a surface void content of 5 to 30% and a BET specific surface area of 30 to 130 m ² /g. It contains 30% by mass or more and 50% by mass or less of calcium and 0.4% by mass or more and 9.5 % by mass or less of aluminum. 0.5 mm or more and 2 mm or less, a water absorption rate of at least 40%, and a uniaxial compressive strength of at least 5 N/mm ² , and the foamed hydrothermally solidified product has a strength of 80% or more with 0.05 M sulfuric acid. and the ratio of water-soluble phosphorus to adsorbed phosphorus is 4.9 % or less.

A second aspect of the phosphorus adsorbent is characterized in that, in the phosphorus adsorbent of the first aspect, the foamed hydrothermally solidified body further contains iron.

A method for producing a phosphorus adsorbent according to a third aspect of the present invention is a method for producing a phosphorus adsorbent comprising a foamed hydrothermally solidified body containing a calcium silicate hydrate comprising an aggregate of needle crystals, The foamed hydrothermally solidified product has a surface void content of 5 to 30% and a BET specific surface area of 30 to 130 m ² /g, and the foamed hydrothermally solidified product is 100% by mass of the foamed hydrothermally solidified product. , contains 30% by mass or more and 50% by mass or less of calcium and 0.4% by mass or more and 9.5% by mass or less of aluminum, and the foamed hydrothermally solidified body is crushed and formed from the formed lump, and is averaged It has a particle size of 0.5 mm or more and 2 mm or less, a water absorption rate of at least 40%, and a uniaxial compressive strength of at least 5 N/mm ² , and the foamed hydrothermally solidified product contains 0.05 M sulfuric acid. and the ratio of water-soluble phosphorus to adsorbed phosphorus is 4.9 % or less, and the following steps (a) to (d) are included.
(a) a mixing step of adding and mixing 5 to 25% by mass of cement containing calcium to 100% by mass of incinerated ash containing aluminum;
(b) After the mixing step, kneading water is added to the mixture of the incinerated ash and cement and kneaded to hydrate the quicklime contained in the incinerated ash and cement to obtain a kneaded product in a funicular state. kneading process,
(c) After the kneading step, the kneaded product of the mixture of incinerated ash and cement and the kneading water is transferred to a mold and hydrothermally solidified while applying a predetermined compressive force to a curing step to obtain a hydrothermally solidified product. ,
(d) After the kneading step, since the solidified body after curing is a molding lump having the size of the molding frame, a crushing step of crushing it to a predetermined particle size.

A method for producing a phosphorus adsorbent according to the fourth aspect is the method for producing a phosphorus adsorbent according to the third aspect,
The incineration ash is any of waste incineration ash such as municipal solid waste, wood chips/tire chips, paper sludge, sewage sludge, and biomass, or incineration ash such as coal, garbage solidified fuel, paper/plastic solidified fuel, etc. or a mixture thereof.

The phosphorus adsorbent of the first aspect of the present invention comprises a foamed hydrothermally solidified body produced mainly from incineration ash, and this foamed hydrothermally solidified body contains at least calcium and aluminum.
This makes it possible to increase the amount of calcium that contributes to phosphorus adsorption, expand the specific surface area, and easily adjust the particle size (that is, easily adjust and form any particle size) compared to the conventional carbonized phosphorus adsorbent. ), the phosphorus adsorption capacity is further increased, and compared to the production equipment that produces carbides, it can be produced easily with inexpensive equipment, so the phosphorus adsorbent becomes inexpensive and commercially profitable. become valuable. Furthermore, the adsorbent that adsorbs and recovers phosphorus retains phosphorus in a form that can be used by plants and can be used as a fertilizer as it is, and the adsorbed phosphorus can be desorbed with a dilute acid solution.
In addition, the foamed hydrothermally solidified material has a surface foaming ratio of 5 to 30% and a specific surface area ratio of 30 to 130 m ² /g. and can adsorb a large amount of phosphorus.
In addition, since the aluminum content is 30 to 50% by mass and 0.4 to 9.5% by mass, the amount of aluminum is greater than that of the phosphorus adsorbent made of carbide, contributing to phosphorus adsorption. do.
In addition, since the average particle size of the foamed hydrothermally solidified product is 0.5 mm or more and 2 mm or less, the pH can be stabilized within the range of the reference value. Since the adsorbent (pulverized solidified material) is used, for example, in a bag, it is possible to prevent clogging between the adsorbents in the bag and decrease in water permeability. Moreover, according to this particle size, the adsorbed and recovered phosphorus can be used as fertilizer as it is.

In the phosphorus adsorbent of the second aspect, since the foamed hydrothermally solidified material further contains iron, the amount of phosphorus adsorbed can be further increased.

According to the method for producing a phosphorus adsorbent of the third aspect of the present invention, it is possible to produce a phosphorus adsorbent that exhibits the same effects as the phosphorus adsorbent of the first aspect. In addition, compared to the phosphorus adsorbent production equipment made of conventional carbides, it is possible to eliminate the need for expensive production equipment and reduce the running cost of operating the production equipment, and it is inexpensive and has a high phosphorus adsorption capacity. We can provide a method for manufacturing materials.

According to the method for producing a phosphorus adsorbent of the fourth aspect, almost all incineration ash can be reused and regenerated into a phosphorus adsorbent or the like. In particular, when incineration ash containing papermaking sludge is used as a raw material, it suppresses the elution of harmful components of heavy metals with a predetermined strength without impairing the porosity and porosity possessed by the incineration ash. can be manufactured as having

1 is a powder X-ray diffraction diagram of a phosphorus adsorbent according to an embodiment of the present invention; FIG. 1 is an electron micrograph showing a fine crystal structure of a phosphorus adsorbent according to an embodiment of the present invention. FIG. 3 shows a measurement test method for phosphorus adsorption, FIG. 3A is a schematic diagram of a batch test, and FIG. 3B is a schematic diagram of a column test. It is the graph which showed the relationship between solution pH and phosphorus removal amount. FIG. 5 shows a comparison of phosphorus adsorption capacity in a column test, FIG. 5A using a prior art coal ash sorbent and FIG. 5B using a phosphorus sorbent according to an embodiment of the present invention. . It is the figure which showed the solution pH after water flow in a column test. FIG. 4 is a diagram showing the state of desorption of adsorbed phosphorus into a solution.

Hereinafter, a phosphorus adsorbent according to an embodiment of the present invention and a method for producing the same will be described with reference to the drawings. However, the embodiments shown below are intended to exemplify the phosphorus adsorbent and the manufacturing method thereof for embodying the technical idea of the present invention, and are not intended to limit the present invention to these. are equally applicable to other embodiments within the scope of the claims.

[Phosphorus adsorbent]
A phosphorus adsorbent according to an embodiment of the present invention will be described with reference to FIGS. 1, 2 and Table 1. FIG. In addition, FIG. 1 is a powder X-ray diffraction diagram of the phosphorus adsorbent according to the embodiment of the present invention, FIG. 2 is an electron micrograph showing the fine crystal structure of the phosphorus adsorbent, and Table 1 shows the embodiment. It is an elemental composition table of the phosphorus adsorbent according to.

The phosphorus adsorbent according to the embodiment of the present invention consists of a foamed hydrothermally solidified body produced using incineration ash as a main raw material, and the hydrothermally solidified body contains a phosphorus component (hereinafter, sometimes simply referred to as "phosphorus" ) containing at least calcium (Ca) and aluminum (Al) elements that combine with . These calcium and aluminum are essential elemental components when producing a foamed hydrothermally solidified body. The phosphorus adsorbent according to the embodiment of the present invention is produced by mixing and kneading a predetermined amount of incineration ash, cement (quicklime), and water, and using a hydrothermal solidification reaction. Cement contains a certain amount of elemental calcium, for example 40% by weight (see Table 1). The aluminum element is also contained in the ash from burning papermaking sludge.

In the relationship between the horizontal axis 2θ and the strength (vertical axis) in FIG. 1, the peak positions marked with triangles indicate calcium silicate hydrate produced by the hydration reaction of cement (quicklime). This calcium silicate hydrate is contained more in the phosphorus adsorbent of the embodiment than in incineration ash as the main raw material. That is, FIG. 1 also shows a powder X-ray diffraction diagram of the main raw material incinerated ash. Although similar, the peak height of the phosphorus adsorbent of the embodiment is higher than that of the incinerated ash as the main raw material. This means that in the phosphorus adsorbent of the embodiment, calcium silicate hydrate is newly produced in the process of producing the foamed hydrothermally solidified product (hereinafter sometimes referred to as production). I get it.

In addition, as shown in FIG. 2, this calcium silicate hydrate consists of aggregates of needle-like crystals with different lengths and thicknesses, and has a different morphology from the conventional carbonized phosphorus adsorbents. It is speculated that This aggregate of needle-like crystals is coarse and dense (fine or porous) and thus has a large area that reacts with the solution. As a result, the aggregate of needle-like crystals comes into contact with the phosphorus-containing solution more and reacts with phosphorus in the solution to efficiently adsorb phosphorus. On the other hand, mainly calcium in calcium silicate hydrate contributes to phosphorus adsorption, and it is presumed that phosphorus is adsorbed and secured in a form readily available to plants. Phosphorus adsorbed on the calcium silicate hydrate can be easily desorbed with a dilute acid solution.

This phosphorus adsorbent is formed of a foamed hydrothermally solidified body mainly composed of incinerated ash and cement, and as shown in Table 1, iron (Fe) , silicon (Si), sulfur (S), zinc (Zn), chlorine (Cl), carbon (C), and so on. Element symbols may be used in the following description.

なお、この表は、各元素の含有割合と粒径との関係をも示しているが、各元素の含有割合は粒径によらず略同じとなっている。

This table also shows the relationship between the content ratio of each element and the grain size, but the content ratio of each element is substantially the same regardless of the grain size.

Among the elemental compositions shown in Table 1, calcium (Ca), aluminum (Al) and iron (Fe) are components that bind to phosphorus, that is, contribute to phosphorus adsorption. As shown in Table 1, the phosphorus adsorbent according to this embodiment contains about 40% by mass of Ca, about 9% by mass of Al, and about 15% by mass of Fe, which are combined with phosphorus, i.e. Adsorbs phosphorus.

Further, the amount of each component shown in the elemental composition in Table 1 changes depending on the type and amount of incinerated ash and cement (quicklime), which are the main raw materials. In particular, Ca varies depending on the amount of cement (quicklime), and as the amount for producing a phosphorus adsorbent made of foamed hydrothermally solidified material, Ca is 30 to 50% by mass with respect to 100% by mass of hydrothermally solidified material. Hereafter, Al is preferably in the range of 0.4 to 9.5% by mass.

With the amounts of Ca and Al within the above ranges, the adsorption amount of the adsorbent of the present embodiment can adsorb (recover) a significantly large amount of phosphorus, for example, 10 times or more, compared to the coal ash adsorbent of the prior art. In addition, this point was verified by the test to be described later.

Moreover, in the phosphorus adsorbent of the present embodiment, it is preferable that the surface void ratio is in the range of 5 to 30% and the BET specific surface area is in the range of 30 to 130 m ² /g. This specific surface area is in a remarkably wide range because the general specific surface area value of coal ash is 0.53 m ² /g. As a result, compared to the adsorbent made of coal ash of the prior art, the surface void ratio and specific surface area are increased, and the phosphorus adsorption surface is enlarged accordingly, and the water absorption rate is increased (for example, 40% or more). The frequency of contact with the phosphorus inside increases, making it possible to adsorb a larger amount of phosphorus.

This foamed hydrothermally solidified product has a water absorption rate of 40% or more and a uniaxial compressive strength of 5 N/mm ² or more by controlling the surface void ratio to 5 to 30% and the specific surface area to 30 to 130 m ² /g. Also, since it becomes a solidified body that also has moisture release properties, it is used not only as a phosphorus adsorbent, but also as various materials that require both water permeability and strength, such as civil engineering materials. becomes possible.

The surface void ratio means the ratio of the area of visible bubbles (voids) in any cross section of the solidified body, and in any cross section (10 mm × 10 mm square) of the solidified body, The surface bubble area (mm ² ) is obtained by measuring the area of bubbles having a possible size with a planimeter, and is calculated by the following formula.
Surface bubble ratio (%) = (Surface bubble area (mm ² )/100 (mm ² )) x 100

In addition, the water absorption rate means the percentage of the total amount of water contained in the solidified body in the surface dry saturated state with respect to the solidified body in the absolutely dry state. The mass in the saturated state (saturated mass) is measured and calculated by the following formula.
Water absorption (%) = ((saturated water mass - absolute dry mass) / absolute dry mass) x 100

Furthermore, even if this solidified body has a surface air bubble ratio of 0%, the air bubbles are too small to be seen visually, and actually have a porous structure. will be prepared. However, if the size of the air bubbles is too small, the connection between the air bubbles decreases, resulting in a decrease in water ^absorption and water permeability. If the specific surface area is 130 m ² /g or less, it is possible to achieve a water absorption of 40% or more even if the surface void content is 0%.

The phosphorus adsorbent of this embodiment has an average particle size of more than 0.5 mm, preferably in the range of 1 mm or more and 2 mm or less. This makes it possible to increase the amount of phosphorus adsorbed without increasing the pH. This point was verified by the test described later.

Adjustment of this particle size can be performed very simply. That is, since the foamed hydrothermally solidified body is produced as a molded lump having an arbitrary size and relatively weak strength, it can be formed into a particle size adjusted to an arbitrary size simply by crushing. In addition, since the carbides of the prior art are granules produced in the form of granules, it is difficult to form them into a particle size adjusted to an arbitrary size by simply crushing them.

From the above description, the phosphorus adsorbent of the present embodiment is, first, compared to the conventional carbonized phosphorus adsorbent, by increasing the amount of calcium that contributes to phosphorus adsorption, expanding the specific surface area, and adjusting the easy particle size. It has a high phosphorus adsorption capacity and is inexpensive. In addition, the pH is stabilized within the range of the standard value, the leaching of phosphorus due to rainfall is small, and phosphorus can be retained in a form that can be used by plants. , the adsorbed and recovered phosphorus can also be desorbed with a dilute acid solution.

Furthermore, the phosphorus adsorbent of the present embodiment eliminates the need for expensive generation equipment and reduces the running cost of operating the generation equipment, compared to the conventional carbonized phosphorus adsorbent generation equipment. can be manufactured in

[Method for producing phosphorus adsorbent]
Next, a method for producing a phosphorus adsorbent according to this embodiment will be described.
The method for producing this phosphorus adsorbent includes the following steps.
(a) A mixing step of adding and mixing 5 to 25% by mass of cement to 100% by mass of incinerated ash containing an amphoteric metal;
(b) After the mixing step, kneading water is added to the mixture of incinerated ash and cement and kneaded to hydrate the lime contained in the incinerated ash and cement to obtain a kneaded product in a funicular state. ,
(c) After the kneading step, the kneaded product of the mixture of incinerated ash and cement and the kneading water is transferred to the mold and hydrothermally solidified while applying a predetermined compression force to obtain a hydrothermally solidified product.
(d) A step of crushing the solidified body after curing to a predetermined particle size, since the solidified body has the size of the molding frame.

In the mixing step (a) above, the incineration ash is the main raw material for the phosphorus adsorbent, and the following are used singly or in combination.
Waste incineration ash such as municipal solid waste, wood chips/tire chips, paper sludge, sewage sludge, biomass, or incineration ash such as coal, waste solidified fuel, paper/plastic solidified fuel, or a mixture of these thing. In other words, dust [ash generated from biomass boilers of paper mills (coal ash, waste tires, wood chips, paper sludge, etc.), fluid sand], cinders (combustion ash of biomass boilers, wood ash such as coconut shells) , shredder dust ash), inorganic sludge (ceramic sludge, metal processing, tunnel excavation sludge, construction sludge, earth and sand, etc.).

These formulations contain dust, chaff and inorganic sludge in predetermined proportions, eg, 70-90% by mass of soot and dust, 10-20% by mass of chaff, and 0-10% by mass of inorganic sludge. In addition, these do not contain harmful substances. With this incineration ash, almost all incineration ash can be reused and regenerated as a phosphorus adsorbent or the like. In particular, when incineration ash containing papermaking sludge is used as a raw material, it suppresses the elution of harmful components of heavy metals with a predetermined strength without impairing the porosity and porosity possessed by the incineration ash. can be manufactured as having

In the mixing step (a) above, if the content of the amphoteric metal such as metallic aluminum in the incinerated ash is too small, hydrogen gas may not be generated sufficiently for foaming. Since the metal itself is irrelevant to the hydrothermal solidification reaction, the amphoteric metal content in the incineration ash is preferably in the range of 0.5 to 10% by mass. According to this range, the phosphorus adsorbent composed of the foamed hydrothermally solidified material contains 0.4 to 9.5% by mass of aluminum.

Further, in the mixing step of (a) above, if lime is added and mixed with the mixture, even if the content of quicklime (CaO) component in the incinerated ash is extremely low, by adding quicklime, digestion The heat of reaction can be generated more actively. In that case, if the addition ratio of lime is too high, the foamed hydrothermally solidified product becomes more alkaline, so the addition ratio of lime should be such that the calcium content of the total mixture is in the range of 30 to 50% by mass. is preferred.

Furthermore, in the mixing step (a) above, the mixture may further contain inorganic sludge as long as it is about 10% by mass of the mixture.

In the mixing step (a) above, if a certain amount of water is added as mixing water to the mixture, the generation of dust during mixing can be reduced, and the digestion reaction of quicklime can be started early, and the following kneading can be performed by slightly moistening the mixture. It is preferable because kneading in the process becomes smooth.

In that case, the addition amount is preferably 15% by mass or more with respect to 100% by mass of the mixture in order to sufficiently suppress the generation of dust. Also, if the amount of mixing water is too large, granulation may occur, which may adversely affect mixing with cement.

Regarding the total amount of water added as the mixing water in the mixing step (a) and the kneading water in the kneading step (b), if it is too small, the viscosity of the kneaded product will be too large and kneading will be difficult. As the amount increases, the kneaded material becomes less viscous and thus easier to knead. Therefore, the total amount of water added as mixing water and kneading water is preferably in the range of 35 to 55% by mass with respect to 100% by mass of the solid component. The temperature of the water to be added is not particularly limited, and hot water of about 98° C. can be used without any problem.

Further, when the kneaded material is hydrothermally solidified, alkaline water reacts with an amphoteric metal such as metallic aluminum contained in the incineration ash to generate gas to foam and expand. If the kneaded material were solidified in the absence of a molding frame, it would expand greatly, and the resulting foamed hydrothermally solidified material would have a surface void ratio of more than 30% and a uniaxial compressive strength of 2 N/mm ² . it will fall below. Therefore, in order to keep the surface void ratio to 30% or less and secure the strength of the solidified product, it is necessary to apply a compressive force to the kneaded product and solidify it in the mold so that the expansion can be kept within a certain range. .

The compressive force to be applied to keep the expansion within a certain range is about 50 kg/cm ² , but it may be appropriately adjusted so that the surface void content is 30% or less. Further, there is no limitation on the mold frame as long as it has strength enough to resist the force in the expansion direction when the kneaded material solidifies. For example, a pit dug in the ground, soil or a stone wall piled up to a predetermined height from the ground surface, or the like can be used as a formwork.

When a vertical hole dug in the ground is used as a forming formwork, the formwork can be obtained by simply digging the ground, which saves costs. Formwork of any length and shape is readily obtained.

In the curing step (c) above, the heat of hydration of the lime component raises the temperature of the kneaded material in the molding form, and the hydrothermal solidification reaction proceeds, and the solidification is completed in about 3 to 8 hours. While the heat of hydration depends on the amount of the kneaded material, the exhaust heat from the kneaded material is proportional to the surface area. There are advantages to using it. In the case of a small formwork, it may be necessary to consider the heat retention of the formwork in order to suppress exhaust heat. The solidified body that has been cured is a molded lump having the size of the molding frame.

In the crushing step (d), the molding block having the size of the molding frame is crushed to a predetermined particle size in the curing step. The average particle size is made larger than 0.5 mm. This particle size is preferably in the range of 1 mm or more and 2 mm or less. This makes it possible to increase the amount of phosphorus adsorbed without increasing the pH.

Adjustment of this particle size can be performed very simply. That is, since it is produced as a relatively weak molded lump of arbitrary size, it can be simply pulverized or crushed and formed into a particle size adjusted to an arbitrary size. In addition, since the carbide is agglomerated in the form of particles, it is difficult to form it into a particle size adjusted to an arbitrary size by simply crushing it.

According to this production method, the calcium content is 30 to 50% by mass, the aluminum content is 0.4 to 9.5% by mass, and the surface A phosphorus adsorbent having a porosity of 5 or more and 30% or less, a BET specific surface area of 30 or more and 130 m ² /g or less, and an average particle size of more than 0.5 mm is manufactured without using special manufacturing equipment. Low cost and easy to manufacture.

Next, the phosphorus adsorbent according to the embodiment of the present invention was verified by conducting the following characteristic tests.

<Phosphorus adsorption>
A batch test and a column test were adopted for the phosphorus adsorption test method. In the batch test, as shown in FIG. 3A, the amount of phosphorus adsorption is calculated from the difference in the concentration of the added phosphorus solution and the supernatant after the reaction, and in the column test, as shown in FIG. In this method, the phosphorus adsorption amount is calculated from the concentration difference between the phosphorus solution before water and the phosphorus solution after water is passed. The molybdenum blue method was used to quantify the phosphorus concentration in the solution.

According to a batch test, the phosphorus adsorbent according to this embodiment was able to adsorb in the range of 1.0 to 594.5 (mgP/g). This range is a value tested by applying different phosphorus concentrations, and the maximum adsorption amount is greater than that of the prior art phosphorus adsorbent made of coal ash. As a result, it was found that the phosphorus adsorbent of this embodiment has an adsorption capacity equal to or greater than that of the conventional phosphorus adsorbent made of coal ash.

Also, the phosphorus adsorption capacity was measured by a column test. As a result of measuring the time required for the phosphorus recovery rate to reach 20%, the conventional phosphorus adsorbent made of coal ash took 10 hours (see FIG. 5A), while the phosphorus adsorbent of this embodiment took 100 hours (see FIG. 5A). See FIG. 5B). As a result, it was found that the phosphorus adsorbent of the present embodiment can treat a phosphorus solution ten times or more than that of the conventional coal ash-based phosphorus adsorbent by passing water through the column.

<pH characteristics>
In a batch test when the pH of the phosphorus solution was adjusted, the results shown in FIG. 4 were obtained. As a result, it was found that the amount of phosphorus adsorbed was not easily affected by the pH of the solution. In addition, the relationship between water passage time and pH was tested. As a result, as shown in FIG. 6, the pH value of the solution after the passage of water remained stable within the reference value throughout.

<Particle size>
Two types of phosphorus adsorbents with different particle sizes were prepared, and a phosphorus solution with a concentration of 1 to 1000 mgP / L was shaken for 1 hour at a solid-liquid ratio of 1: 100 (0.3 g: 30 mL), and the results in Table 2 were obtained. Obtained.

From this result, it can be seen that the finer the particle size, the higher the amount of phosphorus adsorbed, but the higher the pH. Also, if the particle size is coarse, the pH does not increase, but the phosphorus adsorption amount increases. Therefore, the particle size that is neither too fine nor too coarse is preferably more than 0.5 mm and 1 mm or more and 2 mm or less.

<Form of adsorbed phosphorus>
The adsorbed phosphorus was evaluated as a fertilizer component by the Fertilizer Test Method. As a result, the ratio of each form of phosphorus to the adsorbed phosphorus was shown in Table 3.

The results showed that the phosphorus was recovered in a highly plant-available form (soluble) and had little water solubility. As a result, leaching due to rainfall is small, environmental pollution due to leaching into the hydrosphere is prevented, and the recovered phosphorus can be used by plants without waste. In addition, if this characteristic is utilized, by using a phosphorus adsorbent that does not adsorb phosphorus and a general water-soluble phosphorus fertilizer at the same time, it is possible to prevent the leaching of phosphorus fertilizer components due to rainfall, and increase the utilization efficiency of phosphorus fertilizer by plants. It is also possible to use it to improve

<Phosphorus desorption>
Desorption into the adsorbed phosphorus solution gave the results shown in FIG. From this result, it was found that the adsorbed phosphorus can be desorbed with dilute acid. In particular, a high desorption rate of 80% or more was obtained with 0.05M sulfuric acid. As a result, the possibility of reuse as a phosphorus adsorbent can be further expanded.

As explained above, the phosphorus adsorbent of the present invention has an increased amount of calcium that contributes to phosphorus adsorption, has an enlarged specific surface area, and can be adjusted in particle size, etc., as compared with the conventional carbonized phosphorus adsorbent. The synergistic action results in high phosphorus adsorption capacity, low cost and commercial viability.

In addition, the pH is stabilized within the range of the standard value, the leaching of phosphorus due to rainfall is small, and the form is maintained in a form that can be used by plants. Furthermore, the adsorbed/recovered phosphorus can be desorbed with a dilute acid solution.

Furthermore, the method for producing a phosphorus adsorbent of the present invention eliminates the need for expensive production equipment and reduces the running cost of operating the production equipment, compared to the conventional carbonized phosphorus adsorbent production equipment. can be manufactured at low cost.

Claims (4)

As a main raw material, it consists of a foamed hydrothermally solidified body produced by adding 5 to 25% by mass of cement containing calcium to 100% by mass of incinerated ash containing aluminum,
The foamed hydrothermally solidified product contains a calcium silicate hydrate composed of aggregates of needle-like crystals,
The foamed hydrothermally solidified body has a surface void content of 5 to 30% and a BET specific surface area of 30 to 130 m ² /g,
The foamed hydrothermally solidified material contains 30% by mass or more and 50% by mass or less of calcium and 0.4% by mass or more and 9.5% by mass or less of aluminum with respect to 100% by mass of the foamed hydrothermally solidified material,
The foamed hydrothermally solidified body is crushed from a formed lump, has an average particle size of 0.5 mm or more and 2 mm or less, has a water absorption of at least 40%, and has a uniaxial compressive strength of at least 5 N/ ^mm2 ,
A phosphorus adsorbent, wherein the foamed hydrothermally solidified material has a desorption rate of 80% or more with 0.05M sulfuric acid, and a ratio of water-soluble phosphorus to adsorbed phosphorus is 4.9 % or less. 2. The phosphorus adsorbent according to claim 1, wherein said foamed hydrothermally solidified material further contains iron. A method for producing a phosphorus adsorbent comprising a foamed hydrothermally solidified body containing a calcium silicate hydrate comprising an aggregate of needle crystals,
The foamed hydrothermally solidified product has a surface void content of 5 to 30% and a BET specific surface area of 30 to 130 m ² /g,
The foamed hydrothermally solidified material contains 30% by mass or more and 50% by mass or less of calcium and 0.4% by mass or more and 9.5% by mass or less of aluminum with respect to 100% by mass of the foamed hydrothermally solidified material,
The foamed hydrothermally solidified body is crushed from a formed lump, has an average particle size of 0.5 mm or more and 2 mm or less, has a water absorption of at least 40%, and has a uniaxial compressive strength of at least 5 N/ ^mm2 ,
The foamed hydrothermally solidified product has a desorption rate of 80% or more with 0.05 M sulfuric acid, and the ratio of water-soluble phosphorus to adsorbed phosphorus is 4.9 or less,
A method for producing a phosphorus adsorbent, comprising the following steps (a) to (d).
(a) a mixing step of adding and mixing 5 to 25% by mass of cement containing calcium to 100% by mass of incinerated ash containing aluminum;
(b) After the mixing step, kneading water is added to the mixture of the incinerated ash and cement and kneaded to hydrate the quicklime contained in the incinerated ash and cement to obtain a kneaded product in a funicular state. kneading process,
(c) After the kneading step, the kneaded product of the mixture of incinerated ash and cement and the kneading water is transferred to a mold and hydrothermally solidified while applying a predetermined compressive force to a curing step to obtain a hydrothermally solidified product. ,
(d) After the kneading step, since the solidified body after curing is a molding lump having the size of the molding frame, a crushing step of crushing it to a predetermined particle size. The incineration ash is waste incineration ash containing at least one of municipal solid waste, wood chips/tire chips, paper sludge, sewage sludge, and biomass, or coal, garbage solidified fuel, paper/plastic solidified fuel. 4. The method for producing a phosphorus adsorbent according to claim 3, wherein the incineration ash containing at least one of them or a mixture thereof is used.

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