WO2014049897A1

WO2014049897A1 - Phosphorus-collecting agent

Info

Publication number: WO2014049897A1
Application number: PCT/JP2013/001681
Authority: WO
Inventors: 敏弘今田; 祥子宮崎; 秀之辻; 五十川　昌邦; 真理岩下; 忍茂庭; 聡美海老原; 原口　智; 徳介早見
Original assignee: 株式会社東芝
Priority date: 2012-09-25
Filing date: 2013-03-13
Publication date: 2014-04-03
Also published as: JP2014079744A; JP5579296B2

Abstract

It is intended to collect phosphorus, which is contained in waste water such as sewage water in a large quantity and is pointed out as being a depleted resource, with high efficiency and to reuse the phosphorus as a chemical fertilizer. A phosphorus-collecting agent according to an embodiment is a porous body comprising a composition represented by the formula: ((MO)_α(MCO₃)_β(M(OH)₂)_1-α-β)·γSiO₂·δX₂O (wherein 0 ≤ α ≤ 1, 0 ≤ β ≤ 1, 0 ≤ 1-α-β ≤ 1, 0.01 ≤ γ ≤ 20, 0 < δ ≤ 15, M: magnesium and/or calcium, and X: sodium and/or potassium), wherein the pore volume of pores each having a pore diameter of 5 to 500 μm makes up 50 to 85% of the total pore volume.

Description

Phosphorus recovery agent

Embodiments of the present invention relate to a phosphorus recovery agent.

In recent years, due to the rapid globalization of economic activities, global environmental pollution and water pollution have become serious problems. In addition, worldwide production activities simultaneously lead to resource depletion, and the types of elements recognized as rare elements tend to increase. Recently, the reduction of phosphorus ore on a global scale has progressed, and in recent years phosphorus has also been recognized as a rare element.

On the other hand, strict emission standards for phosphorus have been established as countermeasures against eutrophication problems in closed waters such as lakes and bays. As means for removing phosphorus from water (actually in the form of phosphate ions), ions of polyvalent metals such as iron, magnesium, aluminum and calcium are supplied to waste water, and this is combined with phosphate. A reactive agglomeration method is often used in which ions are reacted and solidified or granulated to be removed by precipitation, flotation, filtration, or the like. As a method for supplying polyvalent metal ions into waste water, there is a coagulant addition method in which an aqueous coagulant such as ferric chloride, polyferric sulfate, or polyaluminum chloride is supplied by an injection pump (Patent Document). 1).

In addition to the agglomeration method by addition of such chemicals, an adsorption method using an ion exchange resin, a hydrotalcite-like clay mineral, zirconium oxide or the like is known. This is a method of removing phosphorus by passing phosphorus-containing treated water through a packed bed filled with a phosphorus adsorbent (Patent Document 2). In addition, a method in which granular calcium phosphate-based phosphate ore is used as a seed crystal and filled in a reaction tank, and in the presence of calcium salt, phosphate in waste water is precipitated as calcium phosphate on the surface of the phosphate ore. A crystal that removes phosphorus by using granular ammonium magnesium phosphate as a seed crystal, filling it into a reaction tank, crystallizing ammonium magnesium phosphate on the surface of the seed crystal from waste water containing ammoniacal nitrogen and phosphorus There is an analysis method (Patent Document 3).

However, the above flocculant addition method has low reaction efficiency between phosphoric acid and the flocculant, generates a large amount of sludge, and sludge treatment becomes a problem. In addition, high drug costs are a problem. The adsorption method requires a separate process for recovering the phosphorus adsorbed on the phosphorus adsorbent, and there is a problem that the operation becomes complicated.

Also, the crystallization method has a problem that the fine particles in the desorbed liquid remain without being recovered, and the fine particles become larger during circulation of the process, causing the piping to be blocked. Moreover, since impurities other than phosphorus are recovered in a relatively large amount, the crystallization method such as MAP has a problem that the recovery rate of phosphorus is relatively reduced and the recovery efficiency of phosphorus is low. Furthermore, there is a problem that the cost of phosphorus recovery increases because magnesium salts and the like are expensive.

On the other hand, as described above, phosphorus is recognized as a rare element, and if the adsorbent after adsorbing phosphorus is treated as industrial waste, it results in extra costs. Therefore, reusing phosphorus is an essential requirement. Since phosphorus can be used as a constituent element of chemical fertilizer, phosphorus recovered from water can be reused as chemical fertilizer.

However, chemical fertilizers need to contain two or more of phosphorus, nitrogen and potassium, and it is necessary to contain sodium and silicon as needed. I can't. In the above-described crystallization method using ammonium magnesium phosphate as a seed crystal, ammonium magnesium phosphate can be crystallized on the surface of the seed crystal, so that nitrogen can be secured in addition to phosphorus constituting the chemical fertilizer. However, in this method, potassium cannot be contained, and attempts have been made to add potassium to the recovered ammonium magnesium phosphate to obtain a chemical fertilizer. However, when potassium was added later, only potassium was dissolved into the soil immediately after fertilization, and a chemical fertilizer for practical use could not be obtained.

In other words, in the conventional method, a practical technique for reusing adsorbed phosphorus as a chemical fertilizer has not been established.

JP 2001-048791 A JP 2009-113034 A JP 2004-089931 A

The present invention is intended to efficiently recover phosphorus that is contained in a large amount in wastewater such as sewage and that is depleted as a resource, and to reuse it as a chemical fertilizer.

The phosphorus recovery agent of the embodiment (hereinafter sometimes referred to as “recovery agent” for short) has a general formula ((MO) _α (MCO ₃ ) _β (M (OH) ₂ ) _1-α-β ) · γSiO _2. ΔX ₂ O (0 ≦ α ≦ 1, 0 ≦ β ≦ 1, 0 ≦ 1-α-β ≦ 1, 0.01 ≦ γ ≦ 20, 0 <δ ≦ 15, M: at least one of magnesium and calcium, X: at least one of sodium and potassium), the pore volume having a pore diameter of 5 μm to 500 μm is formed at a ratio of 50% to 85% with respect to the total pore volume, and is porous.

(Phosphorus recovery agent)
The phosphorus recovery agent in the embodiment is ((MO) _α (MCO ₃ ) _β (M (OH) ₂ ) _1-α-β ) · γSiO ₂ · δX ₂ O (0 ≦ α ≦ 1, 0 ≦ β ≦ 1) 0 ≦ 1-α-β ≦ 1, 0.01 ≦ γ ≦ 20, 0 <δ ≦ 15, M: at least one of magnesium and calcium, and X: at least one of sodium and potassium). The porous body has a pore volume of 5 μm to 500 μm with a ratio of 50% to 85% with respect to the total pore volume.

In the above recovery agent, when the recovery agent is immersed in wastewater, since the wastewater generally contains ammonia, ((MO) _α (MCO ₃ ) _β (M (OH)) ₂ ) Magnesium and calcium in the _1-α-β ) part are dissolved as ions and react with ammonium ions (ammonia nitrogen) and phosphate ions (phosphorus) in the wastewater based on the reaction formula shown below. . As a result, reaction products such as magnesium ammonium phosphate, hydroxyapatite, and magnesium phosphate are obtained.

Mg ²⁺ + NH ₄ ⁺ + PO ₄ ^{3 −} + 6H ₂ O → MgNH ₄ PO ₄ .6H ₂ O (1)
10Ca ²⁺ + 2OH ⁻ + 6PO ₄ ³⁻ → Ca ₁₀ (OH) ₂ (PO ₄ ) ₆ (2)
3Mg ²⁺ + 2PO ₄ ^3- → Mg ₃ (PO ₄ ) ₂ (3)

In the wastewater, magnesium ions and calcium ions are sequentially eluted from the surface of the recovery agent. It is held in pores (first pores) of 5 μm to 500 μm. Therefore, the reaction product is stably held against the recovery agent due to the anchor effect on the first pores and the like.

Note that magnesium and calcium that adsorb ammonium ions (ammonia nitrogen) and phosphate ions (phosphorus) in wastewater by ionization as described above are ((MO) _α (MCO ₃ ) _{β in the} above general formula. (M (OH) ₂ ) _1-α-β ). However, such a composition is obtained depending on the raw materials used in the production method described below, and the composition of the composition is the ammonium ion (ammonia nitrogen) and phosphorus of the recovery agent described above. It has no effect on the adsorptivity of acid ions (phosphorus).

Therefore, based on the range of α and β, the composition is composed of MO (α = 1, β = 0), ((MO) _α (MCO ₃ ) _β (M (OH) ₂ ) _1-α-β ) and Even if it has a composition of MCO ₃ (α = 0, β = 1), it does not have any influence on the adsorptivity of ammonium ions (ammonia nitrogen) and phosphate ions (phosphorus) in wastewater.

However, the magnesium content in the recovery agent represented by the above general formula is preferably 4.5% by mass or more and 25% by mass or less. When the magnesium content is less than 4.5% by mass, for example, based on the above reaction formulas (1) and (3), the production amount of the phosphorus-containing magnesium compound decreases, and the phosphorus recovery efficiency is sufficiently increased. It may not be possible to improve. On the other hand, when the magnesium content exceeds 25% by mass, the magnesium amount for producing the phosphorus-containing magnesium compound is saturated, and the drug cost may be improved while the phosphorus recovery efficiency may not be improved. .

Further, the silicon compound of the above general formula (silicic anhydride, silica; SiO ₂ ) is represented by ((MO) _α (MCO ₃ ) _β (M (OH) ₂ ) _1-α-β ) in the general formula. It functions as a substance for holding at least one of a magnesium compound and a calcium compound, that is, a binder. In this case, γ represented by the above general formula needs to be in the range of 0.01 ≦ γ ≦ 20. When γ is less than 0.01, the magnesium compound and calcium compound cannot be sufficiently retained, and when γ is greater than 20, the amount of magnesium compound and calcium compound in the recovery agent is relatively decreased. Since the amount of magnesium (ion) and calcium (ion) that can be supplied to the wastewater is relatively reduced, the recovery efficiency of ammonium ion (ammonia nitrogen) and phosphate ion (phosphorus) in the wastewater is lowered.

By the presence of sodium and potassium in the δX ₂ O portion in the phosphorus recovery agent, the pH of the surface of the phosphorus recovery agent and the pores are inclined to the alkali side, so that magnesium ions in the phosphorus recovery agent and phosphate ions (phosphorus ions in the solution) ) And ammonium ions (ammonia nitrogen) are promoted, so that phosphorus recovery efficiency is increased.

Further, the δX ₂ O portion of the above general formula has the effect of previously containing sodium and potassium, which are chemical fertilizer elements, in the recovery agent as a composition, and the recovery agent of the present embodiment as described above. Is a part that enables the recovery agent after adsorbing ammonium ions (ammonia nitrogen) and phosphate ions (phosphorus) in wastewater to be used as a chemical fertilizer as it is. Therefore, unlike the case where sodium and potassium are added later, it is possible to avoid the problem that only sodium and potassium are dissolved into the soil immediately after fertilization.

ΔX ₂ O also has a role of holding at least one of a magnesium compound and a calcium compound represented by ((MO) _α (MCO ₃ ) _β ) in the general formula, like the silicon compound. .

The OH in the above general formula is taken in by placing the recovery agent or composition obtained by the production method described below in a moisture-containing atmosphere such as the air, It is thought that it does not contribute to recovery.

As described above, in the present embodiment, since the phosphorus and the like adsorbed from the recovery agent cannot be separated and removed, and the recovery agent cannot be reused, the form of reuse is different, but recovery including phosphorus or the like as described above. The agent itself can be reused as a chemical fertilizer. Further, in order to separate phosphorus or the like from the recovery agent, an operation such as a separate separation step is required. However, as in this embodiment, phosphorus or the like adsorbed from the recovery agent is not separated and used as a chemical fertilizer as it is. Thus, the recovered agent can be reused at low cost.

The shape of the recovery agent is not particularly limited, and if necessary, spherical, granular, angular, fibrous, thread-like, rod-like, tubular, sheet-like, film-like Any shape such as a plate-like material can be used. However, it is preferably a spherical object. In this case, for example, when the recovery agent is packed in the column and the wastewater is passed, an appropriate gap is generated between the recovery agents, and the wastewater does not cause a large pressure loss before and after passing through the gap. It flows smoothly and the contact efficiency with the recovery agent is improved, so that phosphorus in the waste water can be recovered efficiently.

However, the recovery agent is a porous body, and magnesium ions and calcium ions are sequentially eluted from the surface of the recovery agent, and the above reaction products such as magnesium ammonium phosphate, hydroxyapatite and magnesium phosphate are removed. A first pore for holding is formed. The pore diameter of the first pore is 5 μm to 500 μm, and the pore volume of the first pore is a ratio of 50% to 85%, preferably 60%, with respect to the whole pores formed in the recovery agent. The ratio is ~ 85%. Further, the phosphorus recovery agent is a porous body as described above, and the porosity is not particularly limited as long as phosphorus recovery is possible. However, in order to recover phosphorus efficiently, the porosity is 30% or more. A range of 70% or less is preferable.

When the ratio of the pore diameter of the first pore is out of the above range, the retention performance of the generated reaction product is deteriorated. Further, when the pore volume of the first pore is less than 50%, the amount of the reaction product that can be retained cannot be sufficiently secured, and the phosphorus recovery efficiency is lowered. On the other hand, if the pore volume of the first pore exceeds 85%, the strength of the recovery agent is extremely reduced, and even if a relatively small external force is applied, the recovery agent may be damaged and cannot be used as the recovery agent. is there. For example, when the recovery agent is packed in a column and wastewater is passed through, it may be damaged by the water pressure of the wastewater.

In the present embodiment, the recovery agent has a volume of pores (second pores) having a pore diameter of 0.005 μm to 5 μm in a ratio of 15% to 50%, further 15% to 40% with respect to the total pore volume. % Is preferably formed. In this case, at least one of magnesium and calcium in the recovery agent is produced on the surface of the recovery agent as a reaction product obtained by, for example, phosphorus in wastewater according to the above reaction formulas (1) to (3), And it can produce | generate in the quantity which can be reliably hold | maintained in the said 1st pore. That is, it is possible to improve the phosphorus recovery efficiency in the wastewater by the recovery agent.

The pore volume, that is, the pore distribution and the pore diameter can be measured by, for example, pore distribution measurement by mercury porosimetry. Moreover, the porosity of the phosphorus recovery agent can also be measured by a mercury intrusion method.

Also, the size can be set as necessary. However, if the size of the recovery agent is too small, the recovery agent is immersed in the waste water, and magnesium ions and calcium ions are dissolved in the waste water, and phosphoric acid obtained according to the above reaction formulas (1) to (3) There is a tendency that the size of reaction products such as magnesium ammonium becomes too fine and is released into waste water. Moreover, it is not preferable when the recovered agent is sprayed as fertilizer. Therefore, in order to avoid such a problem, the size of the recovery agent is preferably on the order of submicron to millimeter, and particularly preferably 0.3 to 5 mm. In addition, the collection | recovery agent of such a magnitude | size can be formed comparatively easily according to the manufacturing method demonstrated below.

In addition, the collection | recovery agent mentioned above is naturally manufactured by the porous and particulate form by manufacturing according to the manufacturing method demonstrated below.

(Method for producing phosphorus recovery agent)
Next, the manufacturing method of the phosphorus collection | recovery agent of this embodiment is demonstrated.

(Mixing process)
First, a raw material for the composition represented by the above general formula constituting the recovery agent of this embodiment is prepared. In addition, according to the kind of raw material, the kind of raw material to prepare can be divided into the following four forms.
(i) at least one of magnesium source and calcium source, silicon source and at least one of potassium source and sodium source
(ii) Magnesium-calcium source, silicon source and at least one of potassium source and sodium source
(iii) at least one of a magnesium source and a calcium source, and at least one of a silicon-potassium source and a silicon-sodium source
(iv) Magnesium-calcium source and silicon-potassium-sodium source

Since the magnesium source is easily available and inexpensive, it can be at least one selected from the group consisting of magnesium hydroxide, magnesium oxide and magnesium carbonate. The calcium source can be at least one selected from the group consisting of calcium hydroxide, calcium oxide and calcium carbonate for the same reason.

The silicon source can be at least one selected from the group consisting of quartz sand, diatomaceous earth, waste glass, fly ash, rice husk, rice husk ash, and steel slag. Among these, fly ash, rice husk, rice husk ash, steel slag, and the like are wastes generated from coal burning, rice threshing, iron refining, etc., but these wastes are silicic acid (silica; Since SiO ₂ ) is contained as a main component, the waste can be effectively used by using these wastes as a silicon source.

Further, the potassium source can be at least one of potassium hydroxide, potassium carbonate and potassium hydrogen carbonate, and the sodium source can be at least one of sodium hydroxide, sodium carbonate and sodium hydrogen carbonate, The calcium source can be at least one of dolomite (CaMg (CO ₃ ) ₂ ) and semi-baked dolomite (MgO · CaCO ₃ ).

The silicon-potassium source can be potassium silicate and the silicon-sodium source can be sodium silicate.

In addition to the above-mentioned inorganic materials, the silicon-potassium source may be rapeseed oil meal, soybean oil meal, cottonseed oil meal, castor oil meal, rice bran oil meal, rice bran, sesame oil meal, peanut oil meal, sunflower oil meal, sweet potato oil, kabok oil meal, corn Vegetable oil cakes such as oil cakes, enjuukasu, tofu residue, tobacco waste, licorice residue, corn germ, etc. Animal meals such as wool, meat, bone meal such as steamed bone meal, shellfish such as steamed fish scales and crab shells, dried yeast such as dried yeast, dried bacteria, dried cocoon cake, potato pupa oil cake, Organic materials such as silk powder such as silk spinning waste, chicken powder, human waste sludge, palm ash, and sewage sludge can be used.

As the silicon-potassium-sodium source, among the above-mentioned organic materials, those containing sodium in particular can be appropriately selected and used.

As is clear from the above (i) to (iv), (ii) to (iv) simplify the manufacturing process of the recovery agent because the types of raw materials used are small compared to (i). be able to.

After preparing the above raw materials, each raw material is weighed and mixed so as to satisfy the element ratio of the composition represented by the general formula. In mixing, an appropriate solvent is used, and an appropriate organic material is used, and the above raw materials and an appropriate organic material are dispersed and stirred in the solvent to form a slurry.

The reason for using the organic material is that the organic material is carbonized in the firing step described below, and as a result, the first pore and the second pore described above are included in the resulting composition (recovery agent). It is because it can form easily in a ratio. Examples of such an organic material include starch, cellulose, methyl cellulose, polyvinyl alcohol, paraffin, β-1,3-glucan, graphite, acrylic resin beads, and the like. Further, when the silicon-potassium source is composed of the above-described organic material, the silicon-potassium source itself is an organic material, so that the first pores and the second pores described above can be used without separately using the above-described starch. Can be easily formed at the above-described ratio.

However, without using such an organic material, the first pores and the second pores described above are described above by appropriately controlling the molding pressure, firing temperature, firing time, and the like in the following molding step and firing step. Can be formed in proportions.

(Molding process)
Next, the slurry (mixture) obtained as described above can be dried, and the granular material obtained using a granulator or the like can be formed into various shapes, for example, extrusion such as strand cutting, sheet cutting, etc. It can shape | mold using arbitrary granulation methods, such as the extrusion molding method including a granulation method, a compression molding method, a pressure molding granulation method, a rolling granulation method, and a rounding method. However, the molding step is not an essential requirement, and the above-described slurry (mixture) can be directly subjected to the firing step described below.

(Baking process)
Next, the molded product obtained in the molding step or the slurry obtained in the mixing step is put in a predetermined mold and subjected to a drying treatment as necessary. Is fired at a temperature of 400 ° C. to 750 ° C. About temperature, it sets suitably according to melting | fusing point of a silicon source. As a result, the raw materials in the mixture (molded product) react with each other to form the composition represented by the above general formula. At this time, the raw material in the mixture (molded product) is decomposed (for example, magnesium carbonate is decomposed and carbon dioxide gas is released to the outside), and further, a part of the raw material is partially liquefied. The resulting composition becomes porous particles.

In addition, before a baking process, a drying process can be performed at the temperature of 50 degrees C or less as needed. Accordingly, the solvent in the slurry can be vaporized and removed at a certain rate, so that the firing time in the firing step can be shortened.

(Crushing process)
Next, the composition obtained as described above is used as a recovery agent having a desired size using a pulverizer or a granulator. In addition, when the molding process is performed as described above, the composition has a desired size in advance, and thus the composition obtained in the firing process can be used as it is as a recovery agent without passing through this process. .

Further, if necessary, acid treatment or washing treatment can be performed on the recovered agent after pulverization or the composition before pulverization. Thereby, residues (potassium salts and the like) can be removed from the recovery agent or the surface of the composition, and the recovery ability of the recovery agent can be improved. In the case of acid treatment, for example, the recovery agent or the composition is immersed in an acetic acid aqueous solution having a concentration of 0.01 mol / L or more and 1 mol / L or less.

In addition, OH in the general formula is taken in by placing the recovery agent or composition obtained as described above in a moisture-containing atmosphere such as the air.

(How to use phosphorus recovery agent)
The usage method of the phosphorus collection | recovery agent of this embodiment is demonstrated.

The method of using the phosphorus recovery agent in this embodiment is very simple, and is performed by bringing the recovery agent obtained as described above into contact with waste water. Thus, the above-described principle, that is, magnesium ions or calcium ions contained in the recovery agent are combined with ammonium ions (ammonia nitrogen) and phosphate ions (phosphorus) in the waste water, thereby causing ammonia nitrogen and It can recover phosphorus. Specifically, preferably, at least one of magnesium and calcium in the recovery agent is released from the second pores onto the surface of the recovery agent, and phosphorus in the wastewater, for example, the above reaction formulas (1) to (3) To produce a reaction product. Thereafter, the reaction product is retained in the first pores, and phosphorus recovery can be performed.

As a specific method for bringing the recovery agent into contact with waste water, for example, the recovery agent is put into waste water, and stirred as necessary to ammonium ions (ammonia nitrogen) and phosphate ions (phosphorus). And a method of sedimentation after recovery. This method is effective when treating a relatively large amount of waste water. According to this method, there is a concern that the water purification equipment becomes relatively large, but there is an advantage that a large amount of waste water can be treated at one time.

In addition, it is possible to collect ammonium ions (ammonia nitrogen) and phosphate ions (phosphorus) in the wastewater by filling the column with the recovery agent and introducing the wastewater into the column. This method is suitable for treating a small amount of waste water because the treatment apparatus is relatively small but the amount of waste water treated is also limited.

In addition, the collection | recovery agent in this embodiment can be applied with respect to waste water of arbitrary pH. However, there is a possibility that the recovery agent dissolves under strong acidity. Therefore, a preferable pH range for applying the ion recovery agent according to the present embodiment is 5.0 or more and 12.0 or less, and a more preferable pH range is 7.0 or more and 10.0 or less. Furthermore, the wastewater may or may not contain carbonate ions, but when carbonate ions are included, the reaction rate between the phosphorus recovery agent and phosphorus increases, which is advantageous in that the phosphorus recovery rate is improved. It is.

Hereinafter, methods for measuring various properties of the phosphorus recovery agents produced in the examples and comparative examples are shown.

[Cu-soluble phosphoric acid content]
The solubility is a characteristic required for phosphate fertilizer and was calculated by the following method. Since the phosphate fertilizer is required to have high solubility, it is preferable that the proportion of the soluble phosphate content eluted with citric acid is high.
Based on the fertilizer analysis method, 1 g of phosphorus recovery agent was shaken with 2% citric acid at 30 ° C. for 1 hour, and the dissolved phosphoric acid was quantified by ICP emission spectrometry.

[Phosphorus recovery rate]
The phosphorus recovery rate was calculated by the following method. The higher the phosphorus recovery rate, the smaller the amount of fine phosphorus products generated in the solution, indicating that phosphorus can be efficiently recovered with the phosphorus recovery agent.
Phosphorus recovery rate (%) = (phosphoric acid amount adhering to the phosphorus recovery agent (mg / L) / phosphoric acid amount removed from the solution by the phosphorus removal test (mg / L)) × 100

[Pore volume]
The pore volume of the phosphorus recovery agent was measured using the following apparatus.
-Trade name manufactured by Shimadzu Corporation; Shimadzu pore distribution measuring device Using an Autopore 9520 type, measurement was performed under conditions of an initial pressure of about 4 kPa.

[Composition evaluation method]
The water content in the phosphorus recovery agent was quantified using the following method.
Elemental analysis of Mg, Ca, Si, Na, and K, which are phosphorus recovery agents, involves completely dissolving a sample by pressure acid decomposition and alkali melting, and then measuring various ion concentrations by ion chromatography or ICP (Inductively Coupled Plasma). ) Measured and quantified using an emission spectrometer. C was measured by a high-frequency combustion overheating-infrared absorption method, and O was measured by an inert gas melting-infrared absorption method. The water content in the phosphorus recovery agent was measured by TG (thermogravimetric analysis). The structure of the phosphorus recovery agent was determined by combining structural analysis such as X-ray diffraction, XPS (X-ray photoelectron spectroscopy), IR (infrared absorption spectrometry) analysis.

(Example 1)
Dolomite (average diameter: 20 [mu] m) and the sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) pure water, 1: 0.8 were mixed with 0.35 weight ratio of slurry A mixture was made. The obtained slurry-like mixture was dried at 50 ° C. for 25 hours using a dryer. Then, it heat-processed at 650 degreeC for 1 hour with the electric furnace. Next, the heat-treated molded body was pulverized so that the particle size was 0.5 mm or more and 1 mm or less. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. Table 1 shows the pore volume of this phosphorus recovery agent.

Next, the phosphorus recovery performance of the obtained phosphorus recovery agent was evaluated. Specifically, 60 mL / L phosphate ion, 500 mg / L ammonia nitrogen, and 1000 mL of 3000 mg / L carbonate ion-containing liquid (pH 8) were prepared as water to be treated. To this aqueous solution, 250 mg of the phosphorus recovery agent obtained above was added and shaken with a shaker to bring phosphate ions and ammonia nitrogen into contact with the phosphorus recovery agent. The contact time and shaking time were 24 hours, and a phosphorus recovery test was conducted. After the test, the phosphorus recovery agent was recovered and the phosphorus recovery rate and solubility were evaluated. The results are shown in Table 1.

(Example 2)
The and powdered sodium silicate _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and pure water, 1: dolomite (20 [mu] m mean diameter): 0.8: except were mixed in 0.2 weight ratio of implementation A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 1.

Next, using the obtained phosphorus recovery agent, a phosphorus recovery test was performed in the same manner as in Example 1, and the phosphorus recovery rate and solubility of the phosphorus recovery product after the test were evaluated. The results are shown in Table 1.

(Example 3)
And the sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) pure water, 1: dolomite (20 [mu] m mean diameter): 0.8: except were mixed in 0.7 weight ratio of implementation A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 1.

(Comparative Example 1)
And the sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) pure water, 1: dolomite (20 [mu] m mean diameter): 0.8: except were mixed in 0.07 weight ratio of implementation A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 1.

(Comparative Example 2)
Dolomite (average diameter: 20 [mu] m) and the sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) pure water, 1: 0.8: except were mixed in a weight ratio of 1.5, implementation A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 1.

Example 4
Dolomite (average diameter: 20 [mu] m) and the beta-1,3-glucan and pure water sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O), 1: 0.8: 0.13: 0 A phosphorus recovery agent was produced in the same manner as in Example 1 except that the mixture was mixed at a mass ratio of 0.7, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 1.

(Example 5)
Dolomite (average diameter: 20 [mu] m) and the beta-1,3-glucan and pure water sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O), 1: 0.8: 0.13: 0 A phosphorus recovery agent was produced in the same manner as in Example 1 except that it was mixed at a mass ratio of .35, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 1.

(Example 6)
Dolomite (average diameter: 20 [mu] m) and the beta-1,3-glucan and pure water sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O), 1: 0.8: 0.13: 1 A phosphorus recovery agent was produced in the same manner as in Example 1 except that the mixture was mixed at a mass ratio of 0.5, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 1.

(Comparative Example 3)
Dolomite (average diameter: 20 [mu] m) and the beta-1,3-glucan and pure water sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O), 1: 0.8: 0.13: 0 A phosphorus recovery agent was produced in the same manner as in Example 1 except that the mixture was mixed at a mass ratio of 0.1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 1.

(Comparative Example 4)
Dolomite (average diameter: 20 [mu] m) and the beta-1,3-glucan and pure water sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O), 1: 0.8: 0.13: 3 A phosphorus recovery agent was produced in the same manner as in Example 1 except that the mixture was mixed at a mass ratio of and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 1.

(Example 7)
And the sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) pure water, 1: dolomite (20 [mu] m mean diameter): 1.2: except were mixed in 0.7 weight ratio of implementation A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 1.33SiO ₂ · 0.66Na ₂ O]. The pore volume was as shown in Table 1.

(Example 8)
And the sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) pure water, 1: dolomite (20 [mu] m mean diameter): 1.2: except were mixed in a weight ratio of 0.5, implementation A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 1.33SiO ₂ · 0.66Na ₂ O]. The pore volume was as shown in Table 1.

Example 9
And the sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) pure water, 1: dolomite (20 [mu] m mean diameter): 1.2: except were mixed in a weight ratio of 1.4, implementation A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 1.33SiO ₂ · 0.66Na ₂ O]. The pore volume was as shown in Table 1.

(Comparative Example 5)
The and powdered sodium silicate _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and pure water, 1: dolomite (20 [mu] m mean diameter): 1.2: except were mixed in 0.2 weight ratio of implementation A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 1.33SiO ₂ · 0.66Na ₂ O]. The pore volume was as shown in Table 1.

(Comparative Example 6)
And the sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) pure water, 1: dolomite (20 [mu] m mean diameter): 1.2: except for mixing 2.8 weight ratio of implementation A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 1.33SiO ₂ · 0.66Na ₂ O]. The pore volume was as shown in Table 1.

(Example 10)
Dolomite (average diameter: 20 [mu] m) and the beta-1,3-glucan and pure water sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O), 1: 1.2: 0.19: 0 A phosphorus recovery agent was produced in the same manner as in Example 1 except that it was mixed at a mass ratio of .85, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 1.

(Example 11)
Dolomite (average diameter: 20 [mu] m) and the beta-1,3-glucan and pure water sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O), 1: 1.2: 0.19: 0 A phosphorus recovery agent was produced in the same manner as in Example 1 except that the mixture was mixed at a mass ratio of 0.5, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 1.

Example 12
Dolomite (average diameter: 20 [mu] m) and the beta-1,3-glucan and pure water sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O), 1: 1.2: 0.19: 1 A phosphorus recovery agent was produced in the same manner as in Example 1 except that the mixture was mixed at a mass ratio of 0.7, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 1.

(Comparative Example 7)
Dolomite (average diameter: 20 [mu] m) and the beta-1,3-glucan and pure water sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O), 1: 1.2: 0.19: 0 A phosphorus recovery agent was produced in the same manner as in Example 1 except that it was mixed at a mass ratio of .2 and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 1.

(Comparative Example 8)
Dolomite (average diameter: 20 [mu] m) and the beta-1,3-glucan and pure water sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O), 1: 1.2: 0.19: 3 A phosphorus recovery agent was produced in the same manner as in Example 1 except that it was mixed at a mass ratio of .4, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 1.

(Example 13)
Dolomite (average diameter: 20 [mu] m) and magnesium oxide (average diameter: 20 [mu] m) and powdered sodium silicate _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and pure water, 1: 0.08: 0.8: Except for mixing at a mass ratio of 0.37, a phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.48 (CaCO ₃ ) _0.5 (Mg (OH) ₂ ) _0.02 · 0.56SiO ₂ · 0.28Na ₂ O]. The pore volume was as shown in Table 1.

(Example 14)
Dolomite (average diameter: 20 [mu] m) and magnesium oxide (average diameter: 20 [mu] m) and powdered sodium silicate _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and pure water, 1: 0.08: 0.8: Except for mixing at a mass ratio of 0.2, a phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.48 (CaCO ₃ ) _0.5 (Mg (OH) ₂ ) _0.02 · 0.56SiO ₂ · 0.28Na ₂ O]. The pore volume was as shown in Table 1.

(Example 15)
Dolomite (average diameter: 20 [mu] m) and magnesium oxide (average diameter: 20 [mu] m) and powdered sodium silicate _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and pure water, 1: 0.08: 0.8: Except for mixing at a mass ratio of 0.74, a phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.48 (CaCO ₃ ) _0.5 (Mg (OH) ₂ ) _0.02 · 0.56SiO ₂ · 0.28Na ₂ O]. The pore volume was as shown in Table 1.

(Comparative Example 9)
Dolomite (average diameter: 20 [mu] m) and magnesium oxide (average diameter: 20 [mu] m) and powdered sodium silicate _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and pure water, 1: 0.08: 0.8: Except for mixing at a mass ratio of 0.1, a phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.48 (CaCO ₃ ) _0.5 (Mg (OH) ₂ ) _0.02 · 0.56SiO ₂ · 0.28Na ₂ O]. The pore volume was as shown in Table 1.

(Comparative Example 10)
Dolomite (average diameter: 20 [mu] m) and magnesium oxide (average diameter: 20 [mu] m) and powdered sodium silicate _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and pure water, 1: 0.08: 0.8: Except for mixing at a mass ratio of 1.5, a phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.48 (CaCO ₃ ) _0.5 (Mg (OH) ₂ ) _0.02 · 0.56SiO ₂ · 0.28Na ₂ O]. The pore volume was as shown in Table 1.

(Example 16)
Magnesium oxide (average diameter: 20 [mu] m) and powdered sodium silicate _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and pure water, 1: 4: except were mixed in a weight ratio of 1.4, Example A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.95 (Mg (OH) ₂ ) _0.05 · 1.4SiO ₂ · 0.71Na ₂ O]. The pore volume was as shown in Table 1.

(Example 17)
Magnesium oxide (average diameter: 20 [mu] m) and the sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) pure water, 1: 4: except were mixed at a mass ratio, as in Example 1 Similarly, a phosphorus recovery agent was produced, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.95 (Mg (OH) ₂ ) _0.05 · 1.4SiO ₂ · 0.71Na ₂ O]. The pore volume was as shown in Table 1.

(Example 18)
Magnesium oxide (average diameter: 20 [mu] m) and the sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) pure water, 1: 4: except were mixed in 2 mass ratio, as in Example 1 Similarly, a phosphorus recovery agent was produced, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.95 (Mg (OH) ₂ ) _0.05 · 1.4SiO ₂ · 0.71Na ₂ O]. The pore volume was as shown in Table 1.

(Comparative Example 11)
Magnesium oxide (average diameter: 20 [mu] m) and powdered sodium silicate _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and pure water, 1: 4: except were mixed in a weight ratio of 0.5, Example A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.95 (Mg (OH) ₂ ) _0.05 · 1.4SiO ₂ · 0.71Na ₂ O]. The pore volume was as shown in Table 1.

(Example 19)
Calcium carbonate (average diameter: 20 [mu] m) and powdered sodium silicate _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and pure water, 1: 0.8: except were mixed in 0.8 weight ratio, A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(CaCO ₃ ) · 0.7SiO ₂ · 0.35Na ₂ O]. The pore volume was as shown in Table 1.

(Example 20)
Calcium carbonate (average diameter: 20 [mu] m) and powdered sodium silicate _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and pure water, 1: 0.8: except were mixed in a weight ratio of 0.5, A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(CaCO ₃ ) · 0.7SiO ₂ · 0.35Na ₂ O]. The pore volume was as shown in Table 1.

(Example 21)
Calcium carbonate (average diameter: 20 [mu] m) and the sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) pure water, 1: 0.8: except were mixed in a weight ratio of 1.5, A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(CaCO ₃ ) · 0.7SiO ₂ · 0.35Na ₂ O]. The pore volume was as shown in Table 1.

(Comparative Example 12)
Calcium carbonate (average diameter: 20 [mu] m) and powdered sodium silicate _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and pure water, 1: 0.8: except were mixed in 0.35 mass ratio, A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(CaCO ₃ ) · 0.7SiO ₂ · 0.35Na ₂ O]. The pore volume was as shown in Table 1.

As is apparent from Table 1, the phosphorus-recovering agents obtained in Examples 1 to 21 have a high soluble phosphate content and phosphorus recovery rate, and the phosphorus-recovering agent of this example has a high soluble phosphate content and phosphorus recovery rate. It was found that the recovery rate was excellent. On the other hand, in Comparative Examples 1 to 12, since the formation ratio of the first pores is outside the scope of the present invention and phosphorus cannot be retained, the soluble phosphonic acid content and the phosphorus recovery rate of the phosphorus recovery agent are It turned out to be low.

(Example 22)
Except for mixing dolomite (average diameter: 20 μm) and aqueous potassium silicate (SiO ₂ 27.5% to 29%, K ₂ O 21% to 23%) in a mass ratio of 1: 2.14 A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.18K ₂ O]. The pore volume was as shown in Table 2.

Next, using the obtained phosphorus recovery agent, a phosphorus recovery test was performed in the same manner as in Example 1, and the phosphorus recovery rate and solubility of the phosphorus recovery product after the test were evaluated. The results are shown in Table 2.

(Example 23)
Dolomite (average diameter: 20 μm) and aqueous sodium silicate (SiO ₂ 36.5% or less, Na ₂ O 18%) were mixed in the same manner as in Example 1 except that they were mixed at a mass ratio of 1: 1.16. The recovery agent was manufactured and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.67SiO ₂ · 0.32Na ₂ O]. The pore volume was as shown in Table 2.

(Example 24)
Phosphorus recovery in the same manner as in Example 1 except that dolomite (average diameter: 20 μm), silica, sodium hydrogen carbonate, and pure water were mixed at a mass ratio of 1: 0.42: 0.59: 0.5. The agent was manufactured and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 2.

(Example 25)
Phosphorus recovery was carried out in the same manner as in Example 1 except that dolomite (average diameter: 20 μm), silica, sodium hydrogen carbonate, and pure water were mixed at a mass ratio of 1: 0.42: 0.38: 0.45. The agent was manufactured and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.18K ₂ O]. The pore volume was as shown in Table 2.

(Example 26)
Dolomite (average diameter: 20 [mu] m) and the beta-1,3-glucan and pure water sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O), 1: 0.8: 0.13: 0 A phosphorus recovery agent was produced in the same manner as in Example 1 except that the mixture was mixed at a mass ratio of 0.7, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 2.

(Example 27)
Dolomite (average diameter: 20 μm), potassium silicate aqueous solution (SiO ₂ 27.5% or more and 29% or less, K ₂ O 21% or more and 23% or less) and β-1,3-glucan 1: 2.14: 0. Except for mixing at a mass ratio of 13, a phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.18K ₂ O]. The pore volume was as shown in Table 2.

(Example 28)
Dolomite (average diameter: 20 μm), silica, sodium bicarbonate, β-1,3-glucan and pure water were mixed at a mass ratio of 1: 0.42: 0.59: 0.13: 0.75. Except for the above, a phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O]. The pore volume was as shown in Table 2.

(Example 29)
Dolomite (average diameter: 20 μm), silica, potassium bicarbonate, β-1,3-glucan and pure water were mixed at a mass ratio of 1: 0.42: 0.38: 0.13: 0.8. Except for the above, a phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.18K ₂ O]. The pore volume was as shown in Table 2.

(Example 30)
And sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and sodium bicarbonate and pure water, 1: dolomite (20 [mu] m mean diameter): 0.8: 0.25: 0.35 by mass of Except for mixing at a ratio, a phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.47Na ₂ O]. The pore volume was as shown in Table 2.

(Example 31)
And sodium silicate powder and _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and potassium hydrogen carbonate pure water, 1: dolomite (20 [mu] m mean diameter): 0.8: 0.38: 0.35 by mass of Except for mixing at a ratio, a phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O · 0.18K ₂ O]. The pore volume was as shown in Table 2.

(Example 32)
Dolomite (average diameter: 20 [mu] m) of sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and the sodium bicarbonate beta-1,3-glucan and the pure water, 1: 0.8: 0 A phosphorus recovery agent was produced in the same manner as in Example 1 except that mixing was performed at a mass ratio of .25: 0.13: 0.71, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.47Na ₂ O]. The pore volume was as shown in Table 2.

(Example 33)
Dolomite (average diameter: 20 [mu] m) of sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and the potassium bicarbonate beta-1,3-glucan and the pure water, 1: 0.8: 0 A phosphorus recovery agent was produced in the same manner as in Example 1 except that it was mixed at a mass ratio of .38: 0.13: 0.35, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O · 0.18K ₂ O]. The pore volume was as shown in Table 2.

(Example 34)
And sodium silicate powder _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and carboxymethylcellulose sodium and pure water, 1: dolomite (20 [mu] m mean diameter): 0.8: 0.25: 0.7 mass Except for mixing at a ratio, a phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.36Na ₂ O]. The pore volume was as shown in Table 2.

(Example 35)
Except for mixing dolomite (average diameter: 20 μm), silica, potassium hydrogen carbonate, sodium carboxymethyl cellulose and pure water in a mass ratio of 1: 0.42: 0.38: 0.2: 0.8. A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.18K ₂ O · 0.03Na]. The pore volume was as shown in Table 2.

(Example 36)
Dolomite (average diameter: 20 [mu] m) and powdered sodium silicate _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and rapeseed oil cake and pure water, 1: 0.8: 0.36: 0.85 weight ratio of A phosphorus recovery agent was produced in the same manner as in Example 1 except that mixing was performed, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O · 0.01K ₂ O]. The pore volume was as shown in Table 2.

(Example 37)
Dolomite (average diameter: 20 [mu] m) and the powdered sodium silicate and _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) β-1,3- glucan and the rapeseed meal and pure water, 1: 0.8: 0. Except for mixing at a mass ratio of 13: 0.36: 0.7, a phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.33Na ₂ O · 0.01K ₂ O]. The pore volume was as shown in Table 2.

(Reference Example 1)
The and powdered sodium silicate _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and pure water, 1: dolomite (20 [mu] m mean diameter): 2: except were mixed with 0.85 weight ratio of Example 1 The phosphorus recovery agent was produced in the same manner as described above, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 1.78SiO ₂ · 0.89Na ₂ O]. The pore volume was as shown in Table 2.

(Reference Example 2)
The and powdered sodium silicate _{_{(Na 2 O · 2SiO 2 ·}} 2.53H 2 O) and pure water, 1: dolomite (20 [mu] m mean diameter): 3.2: except were mixed in a weight ratio of 1.4, implementation A phosphorus recovery agent was produced in the same manner as in Example 1, and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent was [(MgO) _0.39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 2.66SiO ₂ · 1.33Na ₂ O]. The pore volume was as shown in Table 2.

(Reference Example 3)
Calcium and sodium silicate powder carbonate _{_{(Na2O · 2SiO 2 · 2.53H 2}} O) and the pure water, 1: 0.8: except were mixed in 0.6 mass ratio, in the same manner as in Example 1 Phosphorus The recovery agent was manufactured and the characteristics of the phosphorus recovery agent were evaluated. The composition of the obtained phosphorus recovery agent is [CaCO ₃ · 0.7SiO ₂ · 0.35Na ₂ O] [(MgO) _0,39 (CaCO ₃ ) _0.59 (Mg (OH) ₂ ) _0.02 · 0.66SiO ₂ · 0.18K ₂ O]. The pore volume was as shown in Table 2.

As is apparent from Table 2, the magnesium content of the phosphorus recovery agents obtained in Examples 22 to 37 is as high as 4.5% by mass or more, specifically 6.5% by mass or more. It was found that the content of soluble phosphoric acid was also high. That is, it was found that by setting the magnesium content to 4.5 mass% or more and 25 mass% or less, a phosphorus recovery agent having a high soluble phosphate content can be obtained.

On the other hand, the phosphorus recovery agents obtained in Reference Examples 1 to 3 satisfy the requirements of the present invention, but have a lower magnesium solubility than the phosphorus recovery agents obtained in the above examples because of the low magnesium content. It was.

Although several embodiments of the present invention have been described above, these embodiments have been presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

Claims

General formula ((MO) α (MCO 3 ) β (M (OH) 2 ) 1-α-β ) · γSiO 2 · δX 2 O (0 ≦ α ≦ 1, 0 ≦ β ≦ 1, 0 ≦ 1-α -Β ≦ 1, 0.01 ≦ γ ≦ 20, 0 <δ ≦ 15, M: at least one of magnesium and calcium, X: at least one of sodium and potassium), and a pore size of 5 μm to 500 μm A phosphorus recovery agent characterized in that the pore volume is 50% to 85% of the total pore volume and is porous.
The phosphorus recovery agent according to claim 1, wherein the magnesium content is 4.5 mass% or more and 25 mass% or less.
The phosphorus recovery agent according to claim 1 or 2, wherein the volume of pores having a pore diameter of 0.005 to 5 µm is formed at a ratio of 15% to 50% with respect to the total pore volume. Phosphorus recovery agent.
A mixing step of mixing a raw material of the phosphorus recovery agent to obtain a slurry;
The slurry is fired to obtain a general formula ((MO) α (MCO 3 ) β (M (OH) 2 ) 1-α-β ) · γSiO 2 · δX 2 O (0 ≦ α ≦ 1, 0 ≦ β ≦ 1, 0 ≦ 1-α-β ≦ 1, 0.01 ≦ γ ≦ 20, 0 <δ ≦ 15, M: at least one of magnesium and calcium, and X: at least one of sodium and potassium) A firing step in which a pore volume of 5 μm to 500 μm in pore size is formed at a ratio of 50% to 85% with respect to the total pore volume, and forms a porous phosphorus recovery agent;
The manufacturing method of the phosphorus collection | recovery agent characterized by having.
The method for producing a phosphorus recovery agent according to claim 4, further comprising a forming step of forming the slurry into a desired size before firing.
The method for producing a phosphorus recovery agent according to claim 4, further comprising a pulverization step of pulverizing the phosphorus recovery agent obtained through the baking step to obtain a desired size.
To wastewater containing ammonium ions and phosphate ions, the general formula ((MO) α (MCO 3 ) β (M (OH) 2 ) 1-α-β ) · γSiO 2 · δX 2 O (0 ≦ α ≦ 1 0 ≦ β ≦ 1, 0 ≦ 1-α−β ≦ 1, 0.01 ≦ γ ≦ 20, 0 <δ ≦ 15, M: at least one of magnesium and calcium, X: at least one of sodium and potassium) A pore volume having a pore diameter of 5 μm to 500 μm is formed at a ratio of 50% to 85% with respect to the total pore volume, and is in contact with a porous phosphorus recovery agent. , How to use phosphorus recovery agent.
The method for using a phosphorus recovery agent according to claim 7, wherein the pH of the wastewater is 5.0 or more and 12.0 or less.
The method for using a phosphorus recovery agent according to claim 7, wherein the waste water contains carbonate ions.