JP2012144397A - Method for purifying amorphous silica, method for manufacturing inorganic curable composition utilizing this method, and method for manufacturing inorganic cured product - Google Patents

Abstract

A method for purifying amorphous silica from shells to ensure a low-cost source of amorphous silica without using a low-fluidity sodium silicate aqueous solution or the like as a silica source. The provision of the manufacturing method of the inorganic curable composition using the method, and the manufacturing method of an inorganic hardening body.
A shell shell containing a large amount of amorphous silica is burned under a predetermined condition to be taken out while maintaining the state of amorphous silica, and this is used as a silica source, so that low flow This eliminates the need to use a water-soluble sodium silicate aqueous solution or the like as a silica source, and can solve this fluidity problem.
[Selection] Figure 4

Description

  The present invention relates to a method for purifying amorphous silica from a shell, a method for producing an inorganic curable composition using this method, and a method for producing an inorganic cured body.

In recent years, global warming due to carbon dioxide (CO ₂ ) emission has rapidly progressed and has become a social problem. Among them, CO ₂ emissions in the cement industry also account for a large proportion.

The main raw material for large-scale industrial production of cement is limestone. Limestone is mainly composed of calcium carbonate (CaCO ₃ ), and when burned, it is decomposed into calcium oxide (CaO) at about 900 ° C. and simultaneously emits CO ₂ .

Therefore, a technique for producing a concrete-like geopolymer that does not use Portland cement has been attracting attention for the purpose of reducing CO ₂ emissions and effectively utilizing industrial waste.

  As an example, a method using an alkali metal silicate, aluminum silicate such as metakaolin and fly ash is known as a method for producing a highly durable geopolymer.

  When aluminum silicates such as metakaolin and fly ash come into contact with water, the aluminum is eluted, and when this aluminum comes into contact with an aqueous solution of alkali metal silicate containing amorphous silica (water glass), it causes a reaction to crosslink the silicate complex. .

  Patent Document 1 proposes a method for curing a mixture of sodium silicate and fly ash.

JP-A-8-301039

  However, since the aqueous solution of sodium silicate is very viscous, there is a problem that the fluidity is low and it is difficult to handle.

In addition, aluminum silicate has different components depending on the type of commercial products (natural products processed by firing and grinding, by-products such as coal ash). For example, when producing the desired geopolymer, Accordingly, it is necessary to adjust the water glass component to be reacted with aluminum silicate, specifically the silica (SiO ₂ ) to alkali metal oxide (M ₂ O) molar ratio (SiO ₂ : M ₂ O), In most cases, a high-viscosity sodium silicate aqueous solution and a low-viscosity alkali metal hydroxide aqueous solution will be mixed and adjusted. .

  Further, when mixing with the aluminum silicate powder, if the alkali metal silicate aqueous solution has a high viscosity, it is difficult to mix, and the fluidity of the mixture decreases. The handleability is significantly reduced. In addition, low-viscosity potassium silicate and the like are expensive.

  Therefore, it is desired to secure a silica source at low cost without causing the problem of fluidity of the aqueous solution of alkali metal silicate.

  The present invention has been made in view of the above-mentioned problems, and it is possible to provide an amorphous silica from a shell to ensure a low-cost source of highly reactive amorphous silica without causing the above-mentioned fluidity problem. An object is to provide a method for purifying silica, a method for producing an inorganic curable composition using this method, and a method for producing an inorganic cured body.

  The method for purifying amorphous silica according to the present invention is characterized in that the shell is burned.

  The shell shell may be pulverized to a particle size of 200 μm or less, and the shell shell in the purification step may be burned at 700 to 950 ° C. Further, the burning time may be 10 seconds or less, and the shell shell may be rice husk.

  The method for producing an inorganic curable composition according to the present invention includes a step of purifying amorphous silica by any one of the above-described methods for purifying amorphous silica, an aqueous solution of purified amorphous silica and alkali metal hydroxide. And a step of adding aluminum silicate and water to the mixture.

  The manufacturing method of the inorganic hardening body which concerns on this invention is formed using the inorganic curable composition manufactured with the manufacturing method of the said inorganic curable composition, It is characterized by the above-mentioned.

  The shell shell and its ash include those including those pulverized products.

  According to the present invention, by burning the shell shell, other components other than silica contained in the shell shell are removed, and shell shell ash, which is mostly silica, is obtained. This ash is very easy to handle as a silica source as compared with an aqueous solution of sodium silicate, and the above fluidity problem does not occur.

  In addition, if the shell is pulverized to a particle size of 100 μm or less, it efficiently burns during combustion and impurities other than silica are easily removed. For this reason, when producing a geopolymer, the formation reaction of a geopolymer is hard to be inhibited by impurities.

  Furthermore, when the combustion temperature of the shell is 700 to 950 ° C., impurities in the shell are more reliably removed, silica in the shell is difficult to crystallize, and the ratio of the obtained amorphous silica is It will be expensive. Moreover, if the burning time of the shell is 10 seconds or less, the ratio of the obtained amorphous silica increases. Furthermore, if the shell is a rice husk, it is easy to obtain and the amorphous silica can be purified more efficiently.

By mixing the ash of the grain husk and the alkali metal hydroxide, the ash is dissolved to form water glass, so that silica derived from the shell husk can be used, and silica can be procured at low cost. In addition, since the ash derived from the shell is an almost amorphous silica-free powder containing no alkali metal, it can be adjusted to increase the molar ratio of water glass (SiO ₂ : Na ₂ O). is there.

  Furthermore, by adding aluminum silicate and water to amorphous silica, it is possible to prepare an inorganic curable composition and form an inorganic cured body using the same at low cost without any problem of fluidity.

It is the table | surface showing the combustion conditions according to the particle size of each rice husk when aluminum silicate is metakaolin, the fluidity | liquidity of an inorganic curable composition, and the intensity | strength of a hardening body. It is the table | surface which showed the combustion conditions according to the particle size of each rice husk when aluminum silicate was made into fly ash I, the fluidity | liquidity of an inorganic curable composition, and the intensity | strength of a hardening body. It is the table | surface which showed the intensity | strength of the hardening body obtained using a common reagent. It is a figure which shows the combustion conditions of the rice husk of 20 micrometers of average particle sizes, and the intensity | strength of a hardening body. It is a figure which shows the combustion conditions and the intensity | strength of a hardening body of a rice husk with an average particle diameter of 100 micrometers. It is a figure which shows the combustion conditions and the intensity | strength of a hardening body of a rice husk with an average particle diameter of 300 micrometers.

The method for purifying amorphous silica according to the present invention is characterized in that the shell is burned under predetermined conditions.
<Shell shell>
The shell is a rice husk obtained when brown rice is taken out from rice, or a shell of barley, wheat, rye, rice bran, rice bran or millet. It is known that the main components of the shell are amorphous silica and cellulose. In the present invention, this amorphous silica is taken out and used. The use of the silica content of the shell of the shell has been studied so far, but it has been difficult to put the silica into a useful amorphous state, even if it is taken out.
<Crushing shells>
When the shell is pulverized before combustion, the combustion efficiency becomes higher, and amorphous silica can be easily taken out. When pulverized after combustion, the amorphous silica tends to be taken out insufficiently.

  Any method can be used for crushing shell shells, but shell shells are rich in fiber and need to be crushed into fine powder. It is effective to use a pulverizer.

  At this time, the average particle size of the shell is preferably 20 to 200 μm. When the average particle size is less than 20 μm, handling thereof becomes difficult, and pulverization itself to obtain this particle size becomes difficult. On the other hand, if the average particle size exceeds 200 μm, it takes time to burn the shell or the other components such as cellulose tend to be insufficiently burned.

If the combustion is inadequate, a large amount of cellulose network structure remains as impurities in the ash obtained by burning the shell shell, so when mixing the ash and the raw material of the inorganic curable composition, an unnecessarily large amount It absorbs water and becomes difficult to mix.
<Combustion>
The combustion temperature of the shell is preferably 700 to 950 ° C., more preferably 800 to 900 ° C. from the viewpoint that silica is difficult to crystallize and impurities in the shell are suitably removed by combustion. By baking at a temperature in this range, ash containing a large amount of amorphous silica can be prepared from the shell.

  When the combustion temperature of the shell is less than 700 ° C., it takes time until the shell is completely burned as in the case described above. In addition, when combustion tends to be insufficient and a large part of other shell components such as cellulose remain, for example, when producing an inorganic cured body using this ash as described later, geopolymer formation due to impurities The reaction is inhibited and only low strength geopolymers are obtained.

  Conversely, when the shell shell combustion temperature exceeds 950 ° C., the shell shell completely burns in a short time. However, since the silica in the shell shell crystallizes due to combustion, the reactivity decreases. When the polymer is produced, the reaction to form the geopolymer is inhibited and only a low strength geopolymer is obtained. From the above, the strength of the geopolymer is an indicator of the ratio of the obtained amorphous silica.

  Silica generally does not crystallize unless heated to about 1,400 ° C., but the shell shell contains other elements such as potassium and sodium in addition to silica. Even at a combustion temperature of 950 ° C., silica contained in the shell may be crystallized.

  For this reason, when the shell is burned at 700 to 950 ° C., the burning time is preferably set to 10 seconds or less where silica crystals (cristobalite) are hardly generated.

  In order to perform such combustion, a method of ejecting shell husks and air in a heating atmosphere set to about 700 to 800 ° C. in advance and collecting the combustion ash is effective. The combustion of the shell can be suitably performed with, for example, a floating combustion boiler.

By blowing the crushed shell shell into a heating atmosphere at 700 to 800 ° C., combustion at 800 to 900 ° C. can be performed substantially. This is because the shell put into the heating atmosphere is self-ignited and the combustion temperature rises due to the heat of combustion.
<Shell ash ash>
Most of the silica contained in the shell ash obtained by the above combustion is amorphous. When this shell ash is mixed with an aqueous solution of alkali metal hydroxide such as caustic soda or caustic potash, amorphous silica in the shell ash is dissolved in the aqueous solution, and an alkali metal silicate aqueous solution is obtained. . This has the same properties as so-called water glass. It is possible to obtain an alkali metal silicate aqueous solution having an arbitrary molar ratio (SiO ₂ : Na ₂ O) by adjusting the amount of shell ash used.

  Depending on the burning conditions of the grain husk, a grain hull ash having a purity of amorphous silica of 20 to 100% can be obtained. Silica has a purity of 60 to 100%. When the purity of the amorphous silica is less than 60%, it is substantially difficult to produce a geopolymer.

  The alkali metal hydroxide aqueous solution may be any one that has few impurities and a relatively high purity, and is prepared by dissolving granules such as caustic soda, or about 48% aqueous solution that is often used industrially. Good. The alkali metal hydroxide concentration range suitable for dissolution of the shell shell ash silica is 20-60% by weight.

  Since shell shell ash is easy to handle, using shell shell ash as a silica source eliminates the need to handle a highly viscous sodium silicate solution that has been used as a silica source. For example, if the above-mentioned alkali treatment is performed by introducing shell ash into a kneader, an alkali metal silicate aqueous solution can be obtained in the kneader, so that it can be used as it is for preparing an inorganic curable composition.

In addition, as an inorganic curable composition, an alkali metal hydroxide aqueous solution or water mixed with shell ash is also low in viscosity and does not cause viscosity problems during preparation. As a result, the inorganic curable composition or geo Work efficiency in polymer production is improved.
<Preparation of inorganic curable composition>
The inorganic curable composition according to the present invention contains amorphous silica, aluminum silicate, water and the like purified by the above method.

  As aluminum silicate, materials containing aluminum such as metakaolin, fly ash, and slag can be generally used. Any silica or alumina that can be eluted when in contact with an aqueous solution of an alkali metal hydroxide can be used.

  As the raw material of aluminum silicate, it is preferable to use one having an average particle diameter of several μm because the time until the inorganic curable composition is cured and a geopolymer is formed varies depending on the degree of grinding.

  Specifically, metakaolin having an average particle size of about 1.4 μm is preferable. It is preferable to use fly ash having an average particle size of about 3.1 μm.

  As described above, since the silica purity of the resulting shell shell ash is 60 to 100%, for each component of the inorganic curable composition when producing the geopolymer, the shell shell ash 100 A geopolymer can be suitably produced by using about 20 to 400 parts by weight of alkali metal hydroxide, about 80 to 1,900 parts by weight of water, and about 60 to 1,900 parts by weight of aggregate with respect to parts by weight. it can.

Moreover, arbitrary additives, such as aggregates, such as silica sand and a wollastonite, reinforcement fibers, such as vinylon, a weight reduction material, and a foaming agent, can be added. In this case, one having corrosion resistance is desirable.
<Manufacture of geopolymer>
A geopolymer (cured product) is formed by preparing an inorganic curable composition and curing it under predetermined conditions.

  The time and temperature necessary for curing depend on the material (aluminum silicate particle size, etc.) and the temperature from the start to the end of the reaction, but it is preferable to perform at a temperature of 50 to 100 ° C. suitable for the geopolymer formation reaction. A geopolymer can be produced. As the curing, natural curing is preferable, and a method of accelerated curing under heating may be used. The curing time is usually several hours to several tens of hours, but it needs to be adjusted as appropriate because it has a high correlation with the particle size of aluminum silicate.

  Moreover, it is preferable to remove excess water by drying the water that remains without being used in the geopolymer formation reaction by any means such as steam or an electric heater after curing.

Embodiments according to the present invention will be described below with reference to the drawings.
[Example 1]
The following were prepared.
(A1) Rice husk (rice)
(B) Sodium hydroxide solution (NaOH: 27% by weight) 280 g
(C) Metakaolin (BASF Satintone SP-33) 380g
(D) Silica sand (No. 9) ... 380g
(Crushing)
The rice husk (A1) was pulverized to an average particle size of 20 μm with a hammer mill.
(combustion)
The pulverized rice husk was burned in a floating combustion boiler at 600 ° C. for 5 seconds to obtain rice husk ash (A2).
(Preparation of inorganic curable composition)
280 g of sodium hydroxide solution (B) and 100 g of predetermined rice husk ash (A2) are mixed until uniform, and 380 g of metakaolin (C) and 380 g of silica sand (D) are mixed with this mixture until uniform. A curable composition was prepared.

  Moreover, the fluidity | liquidity of this inorganic curable composition was investigated with the following method (refer FIG. 1). In FIG. 1, “◯” indicates liquid, “Δ” indicates mud, and “x” indicates granular (solid state).

As for fluidity, tilt a 100 ml beaker containing 50 ml of the mixture to 45 ° downward, “○” indicates that it starts to flow down immediately, “△” indicates that it takes 3 seconds or more to flow down, and apparently a powder shape remains. Things are marked as “x”.
(Production process of geopolymer)
The prepared inorganic curable composition was poured into a mold (inner dimensions: 250 mm × 75 mm × 20 mm), tapped until uniform, and then held in a 60 ° C. atmosphere for 12 hours. Thereafter, the intermediate molded product was removed from the mold and dried at 60 ° C. for 12 hours. The dried product was measured for bending strength at a span of 200 mm and a load speed of 2 mm / min. The result is shown in FIG.
[Examples 2 and 3]
Example 1 was the same as Example 1 except that the burning time for rice husks was 600 seconds (Example 2) and 3,600 seconds (Example 3).
[Examples 4 to 12]
The combustion temperature of rice husk was set to 800 ° C. (Examples 4 to 6), 900 ° C. (Examples 7 to 9) and 1000 ° C. (Examples 10 to 12), and the combustion time was changed at each combustion temperature. It carried out similarly to -3 (refer FIG. 1).
[Examples 13-24, 25-36]
Example 1 except that the average particle size of the rice husks after pulverization was changed to 100 μm (Examples 13 to 24) and 300 μm (Examples 25 to 36), as shown in FIG. Tests were conducted in the same manner as -12.

The molar ratio of Example _{1~36 (SiO 2: Na 2 O} ) has a near 1.5.
[Reference Example 1]
The bending strength of a geopolymer was investigated when a geopolymer was produced using a commercially available high purity sodium silicate as a silica source.

  The following were prepared.

(A) Sodium silicate aqueous solution (solid content concentration 44%, molar ratio (SiO ₂ / Na ₂ O)) = 1.5) ... 365 g
(C) Metakaolin (BASF Satintone SP-33) 380g
(D) Silica sand (No. 9) ... 380g
The sodium silicate aqueous solution (A) was prepared by mixing commercially available sodium silicate No. 1, 48% by weight sodium hydroxide aqueous solution and distilled water to prepare a sodium silicate solution having a molar ratio of 1.5 and a solid content concentration of 44%. did.

  Except for using sodium silicate as the silica source, 365 g of sodium silicate aqueous solution (A), 380 g of metakaolin (C) and 380 g of silica sand (D) are mixed to prepare an inorganic curable composition, etc. Under the conditions, fluidity measurement, geopolymer production process and bending strength were measured. Each result is shown in FIG.

[Examples 37 to 39]
Unburned rice husks were burned at a combustion temperature of 900 ° C. for a combustion time of 5 seconds (Example 37), 600 seconds (Example 38), and 3,600 seconds (Example 39), and then obtained rice husks. The ash was pulverized with a hammer mill to an average particle size of 20 μm. Then, the inorganic curable composition was prepared similarly to Examples 7-9 using the ground rice husk ash, and the fluidity was measured. Furthermore, the manufacturing process of a geopolymer was performed using the prepared inorganic curable composition, and the bending strength of what was obtained was measured. Each result is shown in FIG.
[Example 40]
The production process of the geopolymer, etc. as in Example 39, except that the unmilled rice husk was burned at a combustion temperature of 1,000 ° C., and the obtained rice husk ash was used for the preparation of the inorganic curable composition without pulverization. Went. Each result is shown in FIG.
[Examples 41 to 43]
In Examples 41 to 43, preparation of an inorganic curable composition and a geopolymer were the same as in Examples 4, 7 and 8 except that fly ash (type I) was used instead of metakaolin. Manufacturing process etc. were performed. Each result is shown in FIG.
(Results and discussion)
<In case of average particle size 20 μm>
FIG. 4 shows a graph of the bending strength of the geopolymers of Examples 1 to 12 formed using amorphous silica taken out from rice husks having an average particle size of 20 μm under different combustion conditions (firing temperature, firing time).

  In addition, the bending strength (23.1 MPa) of the geopolymer when high-purity sodium silicate marketed for reference is used as a silica source (Reference Example 1) is indicated by a broken line as a reference value for high bending strength. This also serves as a reference for measuring the amount of amorphous silica obtained from rice husks.

  Here, when the bending strength of the geopolymer is 10 MPa or more, it can be determined that a curing reaction that forms a substantially sufficient geopolymer has occurred. Moreover, when the bending strength is 20 MPa or more, it can be determined that there is a reactivity (amount and quality of amorphous silica) equivalent to that of factory-produced potassium silicate.

  As shown in FIG. 4, a geopolymer having a bending strength of 20 MPa or more was obtained when the combustion conditions were a combustion time of 5 seconds and a combustion temperature of 800 to 900 ° C. (Examples 4 and 7). These geopolymers have higher bending strength than Reference Example 1 using high-purity sodium silicate as a silica source, and it is particularly preferable to burn rice husks under these conditions.

  This is because burning rice husks with an average particle size of 20 μm under the above combustion conditions yields more amorphous silica than other combustion conditions, resulting in a progress in the formation reaction of the geopolymer, resulting in a high bending strength geopolymer. Because it was formed.

  When the average grain size of the rice husks is 20 μm, the condition that the bending strength of the geopolymer exceeds 10 MPa is that the combustion temperature is about 700 to 980 ° C. when the combustion time is 5 seconds and the combustion temperature is about 600 to 920 when the combustion time is 600 seconds. At a temperature of 3 ° C. and a combustion time of 3600 seconds, the combustion temperature is in the range of about 600 to 870 ° C.

  For example, even if the combustion temperature can only be adjusted to about 600 ° C. depending on the combustion equipment, a high bending strength geopolymer of 20 MPa or more can be obtained by adjusting the combustion time (see Example 3). However, it is preferable to burn rice husk in a short combustion time from the viewpoint of combustion cost.

In addition, the fluidity of the inorganic curable composition was high in each example, and was almost liquid with the fluidity of the inorganic curable composition prepared using commercially available sodium silicate as a silica source (see FIGS. 1 and 3). ).
<In case of average particle size 100 μm>
FIG. 5 shows a graph of the bending strength of the geopolymers of Examples 13 to 24 formed using amorphous silica taken out from rice husks having an average particle size of 100 μm under different combustion conditions (firing temperature, firing time).

  Combustion of rice husk having an average particle size of 100 μm has lower combustion efficiency and a smaller amount of amorphous silica is obtained than when rice husk having an average particle size of 20 μm is used. Therefore, the formation reaction of the geopolymer does not proceed, and the bending strength of the geopolymer is lowered (refer to FIG. 4 and FIG. 5 for comparison).

  Nevertheless, when the combustion conditions are a combustion time of 5 seconds and a combustion temperature of 800 to 900 ° C., a geopolymer having a bending strength of about 17 MPa is obtained (Examples 16 and 19). Even in the case of a combustion time of 600 seconds, a geopolymer of about 15 MPa is obtained under combustion conditions of a combustion temperature of 800 to 850 ° C. (Example 17).

  These geopolymers have a bending strength close to that of 23.1 MPa of Reference Example 1 using high-purity sodium silicate as a silica source, and from this, burning rice husks at a combustion temperature of 800 to 900 ° C. Is particularly preferred.

  When the average grain size of the rice husk is 100 μm, the conditions under which the bending strength of the geopolymer is 10 MPa or more are the combustion temperature of about 700 to 980 ° C. when the combustion time is 5 seconds, and the temperature of about 700 to 920 ° C. when the combustion time is 600 seconds. When the combustion time is 3,600 seconds, the temperature is in the range of about 700 to 840 ° C.

  As can be seen from FIG. 5, when the average grain size of the rice husk is 100 μm, a geopolymer with sufficient bending strength can be obtained only in a narrow combustion temperature range as compared with the case where the average grain size is 20 μm. Therefore, it can be seen that grinding the rice husks to an average particle size of less than 100 μm is effective for taking out the amorphous silica (see FIG. 4 and FIG. 5 for comparison).

In addition, the fluidity of the inorganic curable composition was high in each example except for a part, and it was almost liquid with the fluidity of the inorganic curable composition prepared using commercially available sodium silicate as a silica source (Fig. 1, see FIG.
<In the case of an average particle size of 300 μm>
FIG. 6 shows a graph of the bending strength of the geopolymers of Examples 25 to 36 formed using amorphous silica extracted from rice husks having an average particle size of 300 μm while changing the combustion conditions (calcination temperature and calcining time).

  As shown in FIG. 6, the peak of the combustion temperature suitable for burning the rice husk is shifted to the high temperature side under each combustion time condition. In the case of rice husk having a high average particle size such as an average particle size of 300 μm, a difference in combustion treatment occurs from the outside of the rice husk to the center of the inside because of the large thickness. It is considered that the amorphous silica state is maintained and impurities are removed.

  However, outside the part, impurities are removed by high temperature, but the silica crystallizes.On the other hand, the amorphous part is maintained at the center side of the part, but the impurities remain, so that the combustion process becomes uneven. It is not preferable.

In addition, the fluidity of the inorganic curable composition exhibits low to moderate fluidity in each example, and is inferior to the fluidity of the inorganic curable composition prepared using commercially available sodium silicate as a silica source, and is granular or mud-like. (See FIGS. 1 and 3).
<Change other conditions>
When pulverized unground rice husks and then pulverized to an average particle size of 20 μm (Examples 37 to 40), a geopolymer was obtained only under combustion conditions (Example 39) with a combustion temperature of 900 ° C. and a combustion time of 3,600 seconds. The bending strength was close to 20 MPa (see the broken-line circle symbol in FIG. 4). Therefore, it is desirable to grind the rice husk before combustion.

  Furthermore, from the viewpoint of producing a geopolymer, when Examples 4 and 7 and 8 in which a high bending strength geopolymer was obtained, when metakaolin was changed to fly ash (type I) (Examples 41 to 43), bending strength Decreased (see FIGS. 1, 2 and 4).

  Specifically, the bending strength of the geopolymer decreases from 23.2 MPa (Example 4) to 13.2 MPa (Example 41), and 23.4 MPa (Example 7) to 15.3 MPa (Example 42). And decreased from 13.9 MPa (Example 8) to 9.5 MPa (Example 43).

  From this, it can be seen that metakaolin is more suitable as a raw material for geopolymer than fly ash (type I) (see diamonds, squares, and triangular broken lines in FIG. 4 in order of Examples 41 to 43).

  As described above, the method for purifying amorphous silica of the present invention, the method for producing an inorganic curable composition using the same, and the method for producing an inorganic cured body have been described based on the embodiments and examples. Changes can be made without departing from the invention.

  Although rice husks were used in the examples, amorphous silica can be extracted in the same manner from other rice husks besides rice husks.

  The method for purifying amorphous silica according to the present invention can be used for the preparation of pozzolanic materials such as cement.

Claims (7)

  A method for purifying amorphous silica, characterized by burning shell shells.   The method for purifying amorphous silica according to claim 1, wherein the shell is pulverized to a particle size of 200 μm or less.   The method for purifying amorphous silica according to claim 1 or 2, wherein combustion of the shell is performed at 700 to 950 ° C.   The method for purifying amorphous silica according to any one of claims 1 to 3, wherein the combustion time is 10 seconds or less.   The method for purifying amorphous silica according to any one of claims 1 to 4, wherein the shell is a rice husk.   A step of purifying the amorphous silica in the shell shell by the method for purifying amorphous silica according to any one of claims 1 to 5, and an aqueous solution of the purified amorphous silica and alkali metal hydroxide. And a step of adding aluminum silicate and water to the mixture, and a method for producing an inorganic curable composition.   It forms using the inorganic curable composition manufactured with the manufacturing method of the inorganic curable composition of Claim 6, The manufacturing method of the inorganic hardened | cured material characterized by the above-mentioned.

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