JP2015171696A - Material for recovering phosphorus, production method of the material, and method for recovering phosphorus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material for recovering phosphorus, which exhibits a high phosphorus recovery rate.SOLUTION: The material for recovering phosphorus is obtained by mixing lime with the silica being the easy-to-dissolve silica shown in the following item (1) and contains a single substance of an amorphous calcium silicate hydrate or a combined material which are shown in the following item (2). The item (1) is that the easy-to-dissolve silica is eluted from a mixture obtained by mixing an easy-to-dissolve silica-containing mineral, which is prepared by heating an original mineral to remove organic matter, with an alkali hydroxide aqueous solution having 1 M or higher concentration. The item (2) is that the single substance of the amorphous calcium silicate hydrate having 0.8-20 Ca/Si molar ratio or the combined material obtained by combining Ca(OH)with the amorphous calcium silicate hydrate.

Description

  The present invention relates to a phosphorus recovery material that adsorbs and recovers phosphorus in phosphorus-containing water, a manufacturing method thereof, and a phosphorus recovery method.

  In the past, phosphorus was not produced as a natural resource in Japan, but all depended on imports. However, in recent years, natural phosphorus has been depleted worldwide, and the price of phosphorus has risen, making it difficult to secure phosphorus. Therefore, as one of the means to supplement or substitute for natural phosphorus, a technology for recovering phosphorus from phosphorus-containing water such as wastewater generated at sewage treatment plants using phosphorus recovery materials to make phosphate fertilizer Has been developed.

And the material which has a calcium silicate as a main component is known as said phosphorus collection | recovery material (it is also called a water treatment material, a phosphorus removal material, and a phosphorus collection | recovery material in the following patent document). For example, in the water treatment agent described in Patent Document 1, a substance mainly composed of amorphous calcium silicate hydrate having a CaO / SiO ₂ molar ratio of 1.5 to 5 is heated at 50 to 700 ° C. Manufactured. Moreover, the dephosphorization material of the sewage described in Patent Document 2 is obtained by hydrothermal reaction of a raw material obtained by adding a foaming agent to a water slurry mainly composed of a siliceous raw material and a calcareous raw material under high pressure and high temperature. The resulting amorphous calcium silicate hydrate. Furthermore, the dephosphorization material described in Patent Document 3 is a substantially spherical or hollow pipe-shaped molded product mainly composed of amorphous calcium silicate hydrate.

  However, since the conventional phosphorus recovery material mainly composed of calcium silicate has a slow reaction rate with phosphorus, the reaction time is required to increase the phosphorus content in the phosphorus recovery material recovered by adsorbing phosphorus. It was necessary to lengthen. Moreover, since the phosphorus content in the phosphorus recovery material recovered by adsorbing phosphorus is low, there is a problem that it cannot be effectively used as a phosphate fertilizer.

As a phosphorus recovery material that solves this problem, Patent Document 4 proposes a porous calcium silicate hydrate having an average particle diameter of 150 μm or less and a pore volume of 0.3 cm ³ / g or more. Proposes a porous and amorphous calcium silicate hydrate having an average particle size of 10 μm to 150 μm, a BET specific surface area of 80 m ² / g or more, and a pore volume of 0.5 cm ³ / g or more. .
Further, in Patent Document 6, Ca (OH) ₂ is 2.5 to 80 wt%, Ca / Si molar ratio is 1.0 to 7.0, and amorphous calcium silicate hydrate and Ca (OH). _A phosphorus recovery material comprising a composite of ₂ has been proposed. The phosphorus recovery material is excellent in the performance of adsorbing phosphorus, and the composite adsorbing phosphorus has a high sedimentation property, so that it has a high phosphorus removal effect and can shorten the processing time (paragraph 0009).
Furthermore, in Patent Document 7, drainage is performed using amorphous calcium silicate hydrate alone or a composite of the hydrate and Ca (OH) ₂ having a Ca / Si molar ratio of 0.8 to 20. A method for recovering the phosphorus in it has been proposed.

JP-A 61-263636 Japanese Examined Patent Publication No. 02-020315 JP-A-10-235344 JP 2009-285635 A JP 2009-285636 A JP 2012-50975 A JP 2013-27865 A

  An object of the present invention is to provide a phosphorus recovery material and the like that have the advantages of the phosphorus recovery material proposed in Patent Document 6 and have a high fertilizer effect.

The inventor has examined phosphorus recovery materials that meet the above-mentioned object, and found that the following phosphorus recovery materials can meet the above-mentioned object, thereby completing the present invention. That is, this invention is the phosphorus collection | recovery material which has the following structure, its manufacturing method, and a phosphorus collection | recovery method.
[1] Amorphous calcium silicate hydrate alone or amorphous calcium silicate hydrate of the following (2) formed by mixing lime and silica of (1) below and Ca (OH) ₂ Phosphorus recovery materials, including composites.
(1) Easily soluble silica obtained by mixing and eluting an easily soluble silica-containing mineral from which organic substances have been removed by heat treatment and an aqueous alkali hydroxide solution having a concentration of 1 M or more (2) molar ratio of Ca / Si 0.8-20, amorphous calcium silicate hydrate alone or a composite of amorphous calcium silicate hydrate and Ca (OH) ₂
[2] The phosphorus recovery rate is 70% or more when the calcium content in the phosphorus recovery material and the phosphorus content in the phosphorus-containing water are mixed so that the molar ratio of Ca / P is 2.0. The material for recovering phosphorus according to [1].
[3] The phosphorus recovery material according to [1] or [2], wherein the phosphorus recovery material recovered by adsorbing phosphorus has a soluble phosphoric acid concentration of 15% or more.
[4] A method for producing a phosphorus recovery material according to any one of [1] to [3], comprising at least the following steps (A) to (D): .
(A) A heat-treating step of a readily soluble silica-containing mineral by heating the easily soluble silica-containing mineral to thermally decompose and remove organic matter in the mineral (B) The heat-treated easily soluble silica-containing mineral and , An elution step of easily soluble silica in which an alkali hydroxide aqueous solution having a concentration of 1M or more is mixed and stirred to elute the readily soluble silica in the mineral. After adjusting the pH by mixing and precipitating the dissolved impurities, the eluate is purified by solid-liquid separation to remove the precipitated impurities, thereby easily dissolving the eluate of easily soluble silica. (D) After adjusting the concentration of silica by adding water to the eluate of the purified easily soluble silica, Ca in lime and the eluate of the purified easily soluble silica The Ca / Si molar ratio of Si is 0.8-20. As described above, by mixing the eluate with lime to produce a stirring amorphous calcium silicate hydrate, amorphous calcium silicate hydrate alone or amorphous calcium silicate hydrate and Ca (OH) ₂ A slurry production process for obtaining a slurry of a composite with
[5] A phosphorus recovery method for obtaining a phosphorus recovery material obtained by adsorbing phosphorus after mixing phosphorus-containing water and the phosphorus recovery material according to any one of [1] to [3].

  The phosphorus recovery material of the present invention has a high phosphorus recovery rate, and the phosphorus recovery material after adsorbing and recovering phosphorus has a high soluble phosphoric acid concentration. Therefore, the phosphorus recovery material of the present invention is suitable as a material for recovering phosphorus from phosphorus-containing water generated at a sewage treatment plant or the like to produce a phosphate fertilizer.

It is a figure which shows the powder X-ray-diffraction peak of the siliceous shale (easily soluble silica containing mineral) used in the Example. It is a flowchart which shows the manufacturing method of the phosphorus collection | recovery material of this invention in an Example.

Hereinafter, the present invention will be described by dividing it into phosphorus recovery materials, manufacturing methods thereof, and phosphorus recovery methods.
1. Phosphorus Recovery Material The phosphorus recovery material of the present invention is an amorphous calcium silicate hydrate simple substance (hereinafter referred to as “CSH”) formed by mixing lime and readily soluble silica, or CSH and Ca (OH). ₂ (hereinafter referred to as “CSH composite”).
Here, CSH refers to calcium silicate hydrate excluding crystalline tobermorite and xonotlite. The CSH composite is a composite that CSH is generated by taking in Ca (OH) ₂ generated from excess lime, and is a composite in which Ca (OH) ₂ is dispersed inside CSH. It is a thing. The composite is a substance different from a mixture obtained by simply mixing CSH and Ca (OH) ₂ , and the sedimentation property of the composite is higher than the sedimentation property of the mixture.

The readily soluble silica is a silica obtained by elution by mixing an easily soluble silica-containing mineral with a 1 M or higher alkali hydroxide aqueous solution after removing organic substances by heat treatment. The easily soluble silica-containing mineral from which organic matter has been removed has less organic matter contained in the produced phosphorus recovery material than the readily soluble silica-containing mineral from which organic matter has not been removed, so the organic matter is added to the phosphorus-containing water to be treated. There is no concern about elution, and there is an advantage that BOD and COD do not increase. Moreover, when 1 M or more of alkali hydroxide aqueous solution is used, the elution rate of easily soluble silica will become large. The concentration of the aqueous alkali hydroxide solution is preferably 2M or more.
The readily soluble silica-containing mineral is a silica material containing alkali-soluble silica that dissolves in an alkali solution under normal pressure conditions, preferably under heating at 30 ° C. or higher. Examples of the readily soluble silica material include one or more selected from the group consisting of siliceous shale, amorphous silica, silica gel, silica fume, opal, and diatomaceous earth.
The alkali hydroxide is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide and the like.
The lime is at least one selected from the group consisting of slaked lime, quick lime, calcium hydroxide, and calcium oxide.

The molar ratio of Ca / Si in the CSH or CSH composite is 0.8-20. When the molar ratio is less than 0.8, phosphorus is not sufficiently adsorbed. When the molar ratio exceeds 20, calcium hydroxide becomes excessive and sedimentation properties decrease. The molar ratio of Ca / Si is preferably 0.9 to 15, more preferably 1.0 to 10. Incidentally, the content ratio of Ca (OH) _{2 in} the CSH composite is about 10% by mass when the molar ratio of Ca / Si is 1.5, about 50% by mass at 5.5, and about 62% by mass at 10. 20 is about 86% by mass.

Further, the phosphorus recovery rate of the phosphorus recovery material of the present invention is preferably when the calcium content in the material and the phosphorus content in the phosphorus-containing water are mixed so that the molar ratio of Ca / P is 2.0. Is 70% or more, more preferably 90% or more. If this value is 70% or more, phosphorus in phosphorus-containing water can be efficiently recovered. The phosphorus recovery rate is calculated by the following formula.
R = 100 × (P ₀ −P) / P ₀
In the formula, R represents the phosphorus recovery rate (%), P ₀ represents the phosphorus concentration (mg / L) in the phosphorus-containing water before adding the phosphorus recovery material, and P added the phosphorus recovery material. The phosphorus concentration (mg / L) in the filtrate obtained by filtering phosphorus-containing water after adsorbing and recovering phosphorus is expressed.

  Moreover, the soluble phosphoric acid concentration of the material for recovering phosphorus after adsorbing and recovering phosphorus is preferably 15% or more, more preferably 20% or more. If the value is 15% or more, the material can be used as a phosphate fertilizer having a high fertilizer effect. By the way, according to the official standard of ordinary fertilizer established based on the Fertilizer Control Law (February 22, 1986, Ministry of Agriculture, Forestry and Fisheries Notification No. 284), by-product phosphate fertilizer has a soluble phosphate concentration of 15% or more. It is prescribed.

2. Method for Producing Phosphorus Recovery Material The production method comprises (A) a heat treatment step for a readily soluble silica-containing mineral, (B) an elution step for easily soluble silica, (C) a purification step for easily soluble silica, and (D ) A manufacturing method including at least a slurry preparation step. Hereinafter, the steps (A) to (D) will be described separately.

(A) Heat-treating step of easily soluble silica-containing mineral This step heats easily-soluble silica-containing mineral (including pulverized product thereof) using a heating device such as an electric furnace or a rotary kiln, It is a process of removing organic matter inside by thermal decomposition. Easily soluble silica-containing minerals, excluding organic matter, have the advantage that organic matter is not contained in the phosphorus-containing water to be treated because there is little organic matter contained in the produced phosphorus recovery material, and BOD and COD do not increase There is.
The heating temperature is preferably 400 ° C. or higher, more preferably 500 ° C. or higher, still more preferably 600 ° C. or higher, and the upper limit is 1000 ° C. When the value is less than 400 ° C., the heat treatment takes time, and when it exceeds 1000 ° C., the readily soluble silica tends to decrease.
The heating time depends on the particle size of the mineral, but is preferably 1 hour or longer, more preferably 2 hours or longer, and further preferably 3 hours or longer.
The content of the organic matter after the heat treatment is preferably 5% by mass or less, more preferably 3% by mass or less, and still more preferably 1% by mass or less.

(B) Elution process of easily soluble silica The process comprises mixing the heat-treated easily soluble silica-containing mineral and an alkali hydroxide aqueous solution having a concentration of 1M or more and stirring the easily soluble silica in the mineral. Is a step of eluting.
When an aqueous alkali hydroxide solution having a concentration of 1 M or more is used, the elution rate of readily soluble silica increases and the amount of elution increases. The mixing amount of the aqueous alkali hydroxide solution depends on the content of the easily soluble silica in the easily soluble silica-containing mineral, but preferably 100 to 100 parts by weight of the easily soluble silica-containing mineral contains 100 to 100 parts of the alkali hydroxide aqueous solution. 3000 parts by mass.
The temperature of the aqueous solution at the time of mixing and stirring may be room temperature, but is preferably 50 ° C. or higher, more preferably 60 ° C. or higher, and further preferably 70 ° C. or higher in order to further improve working efficiency. When the value is 50 ° C. or higher, the elution rate of the readily soluble silica is remarkably increased.
Moreover, although the said stirring time is based also on the temperature of the said aqueous solution, Preferably it is 30 minutes or more, More preferably, it is 1 hour or more.

(C) Purification step of easily soluble silica The eluate of the easily soluble silica and an acid are mixed to adjust the pH, and the dissolved impurities are precipitated, and then the eluate is separated into solid and liquid. This is a step of purifying the eluate of readily soluble silica by removing the precipitated impurities.
Examples of the acid include one or more selected from the group consisting of inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid.
Moreover, the range of the said pH is the range of the pH from which impurities, such as dissolved aluminum and iron, precipitate, Preferably it is 8-13, More preferably, it is 9-12, More preferably, it is 10-11. Impurities such as aluminum and iron present in the liquid form a sparingly soluble salt with the phosphate, reducing the phosphorus in the phosphorus-containing water that should be adsorbed by the phosphorus recovery material. When the material for recovering phosphorus collected by adsorbing is used as phosphate fertilizer, the fertilizer effect is low because the soluble phosphorus concentration is low.
Examples of the solid-liquid separation means include filtration, suction filtration, decantation, and centrifugal separation.

(D) Slurry preparation process After adjusting the concentration of silica by adding water to the purified eluate of the easily soluble silica, Ca in lime and the eluate of the purified easily soluble silica In this process, lime is added to the eluate and stirred to produce CSH so that the molar ratio of Si to Ca / Si is 0.8 to 20, thereby obtaining a slurry of CSH or CSH composite.
The concentration of the silica is preferably adjusted so that the silica (SiO ₂ ) concentration in the eluent of easily soluble silica is 5% by mass or less. When the value exceeds 5% by mass, when the lime is mixed, the eluate is gelled and stirring becomes difficult, and the composition of CSH and the like may become nonuniform.
The lime is preferably mixed in a slurry so as not to become non-uniform when mixed with the eluent of readily soluble silica.

  The method for producing a phosphorus recovery material of the present invention includes the steps (A) to (D) as essential steps, and also includes the following (E) drying step of CSH or CSH composite as an optional step. You can also. That is, as the phosphorus recovery material of the present invention, the CSH or CSH composite slurry obtained in the step (D) may be used, and the dried CSH or CSH composite dried product (powder or granules) Body etc.) may be used. Then, when using a dried material as the phosphorus collection | recovery material of this invention, the manufacturing method of the phosphorus collection | recovery material of this invention further includes the following (E) process as an arbitrary process.

(E) Drying step of CSH or CSH composite This step is a step of obtaining a dried product of CSH or CSH composite by drying the slurry or a liquid obtained by removing impurities from the slurry by filtration or the like. Drying makes the phosphorus recovery material of the present invention easier to store and transport. In addition, when the dried product is obtained in the form of a lump, it may be pulverized or ground to obtain a powder or granule.

3. Phosphorus Recovery Method The recovery method is a method for obtaining phosphorus-recovered material that adsorbs phosphorus after mixing phosphorus-containing water and the phosphorus-recovery material (CSH or CSH composite). Here, the phosphorus-containing water is not particularly limited, and examples thereof include sewage sludge separation liquid and factory waste liquid containing phosphorus.
The phosphorus recovery material can be used for recovery of phosphorus in the form of a slurry or a dried product. However, if the phosphorus recovery material is not uniformly mixed when used in the form of a powder, the powder is preferably preliminarily mixed. Use as a slurry.
The phosphorus recovery material adsorbing phosphorus is separated and recovered by filtration, sedimentation separation, or centrifugation. The phosphorus recovery material recovered here is suitable as a phosphate fertilizer or a raw material thereof because it has a high soluble phosphorus concentration as described in paragraph 0029.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.
1. Materials used (1) Easily soluble silica-containing minerals Silica shale from Hokkaido (chemical composition: SiO ₂ 80 mass%, Al ₂ O ₃ 10 mass%, Fe ₂ O ₃ 5 mass%)
(2) Sodium hydroxide reagent grade 1 (manufactured by Kanto Chemical Co., Inc.)
(3) Slaked lime Special slaked lime as defined in JIS R 9001: 2006 (manufactured by Yakusen Lime)

2. Manufacture of phosphorus recovery material The phosphorus recovery material of the example was manufactured through the following steps (A) to (E). FIG. 2 shows a flowchart of the manufacturing method.
(A) Heat treatment process of easily soluble silica-containing mineral 250 g of crushed siliceous shale was placed in an electric furnace and heated at 600 ° C. for 3 hours to thermally decompose and remove organic matter in the siliceous shale.
(B) Elution process of easily soluble silica After adding 1000 g of 2M sodium hydroxide aqueous solution to the heat-treated siliceous shale, the mixture was heated to 70 ° C. and stirred for 1 hour to easily dissolve in the siliceous shale. Silica was eluted.
(C) Purification step of readily soluble silica After adding sulfuric acid to the eluate of the easily soluble silica to adjust the pH to 10.5 and precipitating impurities such as aluminum and iron that had been eluted, the eluate The insoluble matter containing the precipitate was removed by solid-liquid separation by suction filtration using filter paper, and the eluate of readily soluble silica was purified.
(D) Slurry production process 2000 g of distilled water was added to 1000 g of the eluate of the purified readily soluble silica to adjust the concentration of silica to 3.3% by mass. Next, 120 g of slaked lime is added to the eluate so that the Ca / Si molar ratio of Ca in the slaked lime and the purified easily soluble silica eluate is 1.0, and the mixture is stirred at room temperature for 1 hour. CSH was produced to obtain a slurry of the CSH.
(E) CSH Drying Step A liquid obtained by suction filtration of the slurry was dried at 105 ° C. for 24 hours to obtain a dry powder of CSH (hereinafter referred to as “phosphorus recovery material A”).

Moreover, in order to use the phosphorus collection | recovery material (phosphorus collection | recovery material) of patent document 6 for a comparative example, the collection material was manufactured according to the method of paragraph 0030 of patent document 6. FIG. That is, the method described in Paragraph 0030 of Patent Document 6 omits (A) the heat treatment step of siliceous shale and (C) the purification step of readily soluble silica in the method for producing phosphorus recovery material A. Is the method. Specifically, the phosphorus recovery material of the comparative example was manufactured through the following steps (i) to (iii).
(I) Elution process of easily soluble silica After heating 1000 g of 0.125M sodium hydroxide aqueous solution to 70 ° C., 250 g of crushed siliceous shale not heated was added thereto at 70 ° C. The mixture was stirred for 1 hour, and the readily soluble silica in the siliceous shale was eluted to obtain an easily soluble silica eluate.
(ii) Hydrothermal synthesis step of CSH After adding slaked lime to the eluate maintained at 70 ° C. so that the Ca / Si molar ratio is 1.0, the mixture is stirred for 1 hour at 70 ° C. and hydrothermal. Amorphous calcium silicate hydrate was produced by synthesis to obtain a slurry of CSH.
(Iii) CSH drying step The CSH slurry is decanted to separate the insoluble matter and the supernatant containing the CSH, and the supernatant containing the CSH is dried at 105 ° C. for 24 hours. A powder (hereinafter referred to as “phosphorus recovery material B”) was obtained.
Comparing the contents of aluminum and iron in the phosphorus recovery material A and phosphorus recovery material B, the aluminum content is 0.1% by mass and 4.3% by mass, respectively, and the iron content is 0.00%. Since the content of carbon is 05% by mass and 1.1% by mass, and the carbon content is 0.005% by mass and 0.2% by mass, respectively, the phosphorus recovery material A is less in impurities such as aluminum than the phosphorus recovery material B. It can be seen that the amount is significantly less than 1/10.

2. Phosphorus recovery test Phosphorus recovery material A and phosphorus recovery material B in sewage sludge desorption liquid (phosphorus-containing water) with a PO ₄ -P concentration of 100 mg / L in calcium and sludge desorption liquid The phosphorus content was added as a slurry so that the molar ratio of Ca / P was 2.0 and stirred at room temperature for 1 hour. After 1 hour, the concentration of phosphorus in the sewage sludge desorbed liquid was measured according to the molybdenum blue spectrophotometric method prescribed in JIS K 0102 “Factory Wastewater Test Method”. The results are shown in Table 1.
From Table 1, all of the Examples and Comparative Examples have a high phosphorus recovery rate of 90% or more, and have an excellent phosphorus recovery effect.

3. Measurement of the concentration of soluble phosphoric acid in the phosphorus recovery material After the phosphorus recovery material obtained by adsorbing and recovering phosphorus in the phosphorus recovery test (hereinafter referred to as “phosphorus recovery material”) is filtered, The collected material was dried at 105 ° C. for 12 hours. Next, based on the fertilizer test method, the soluble phosphoric acid concentration in the dried phosphorus collection was measured.
As a result, the concentration of soluble phosphoric acid was 20.4% for the phosphorus recovery material derived from the phosphorus recovery material A and 16.8% for the phosphorus recovery material derived from the phosphorus recovery material B.
As described above, the phosphorus recovery rate of the phosphorus recovery material A and the phosphorus recovery material B is the same as described above, but the soluble phosphate concentration is one of the important indicators of the fertilizer effect. The phosphorus recovery material A is 1.2 times higher than the phosphorus recovery material B. Therefore, it can be said that the phosphorus recovery material of the present invention has a higher fertilizer effect than the phosphorus recovery material proposed in Patent Document 6.

Claims (5)

(2) Amorphous calcium silicate hydrate alone or composite of amorphous calcium silicate hydrate and Ca (OH) ₂ formed by mixing lime and silica (1) below Material for collecting phosphorus, including waste.
(1) Easily soluble silica obtained by mixing and eluting an easily soluble silica-containing mineral from which organic substances have been removed by heat treatment and an aqueous alkali hydroxide solution having a concentration of 1 M or more (2) molar ratio of Ca / Si 0.8-20, amorphous calcium silicate hydrate alone or a composite of amorphous calcium silicate hydrate and Ca (OH) ₂   The phosphorus recovery rate is 70% or more when the calcium content in the phosphorus recovery material and the phosphorus content in the phosphorus-containing water are mixed so that the molar ratio of Ca / P is 2.0. The phosphorus recovery material described.   The phosphorus recovery material according to claim 1 or 2, wherein the phosphorus recovery material recovered by adsorbing phosphorus has a soluble phosphoric acid concentration of 15% or more. It is a manufacturing method of the phosphorus collection | recovery material of any one of Claims 1-3, Comprising: The manufacturing method of the phosphorus collection | recovery material at least including the following (A) process-(D) process.
(A) A heat-treating step of a readily soluble silica-containing mineral by heating the easily soluble silica-containing mineral to thermally decompose and remove organic matter in the mineral (B) The heat-treated easily soluble silica-containing mineral and , An elution step of easily soluble silica in which an alkali hydroxide aqueous solution having a concentration of 1M or more is mixed and stirred to elute the readily soluble silica in the mineral. After adjusting the pH by mixing and precipitating the dissolved impurities, the eluate is purified by solid-liquid separation to remove the precipitated impurities, thereby easily dissolving the eluate of easily soluble silica. (D) After adjusting the concentration of silica by adding water to the eluate of the purified easily soluble silica, Ca in lime and the eluate of the purified easily soluble silica The Ca / Si molar ratio of Si is 0.8-20.0. So that, by mixing the eluate with lime to produce a stirring amorphous calcium silicate hydrate, amorphous calcium silicate hydrate alone or amorphous calcium silicate hydrate and Ca (OH) _2. Slurry production process for obtaining a slurry of a composite with ₂   The phosphorus collection | recovery method of obtaining the phosphorus collection | recovery material which adsorb | sucked phosphorus, after mixing phosphorus containing water and the phosphorus collection | recovery material of any one of Claims 1-3.

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