Porous silica-clay composite material, water purifying agent including porous silica-clay composite material, porous silica-clay composite material-including powder for soil, and porous silica-clay composite material production method

Abstract

This porous silica-clay composite material has a specific surface area of 1080 m2 / g or more, wherein the content ratio [[clay material / (clay material + silica)] × 100] of the clay material to the sum of the clay material and silica is 1%-10% in terms of weight%.

Description

Porous silica-clay composite material, water purification agent containing porous silica-clay composite material, soil powder containing porous silica-clay composite material, and method for producing porous silica-clay composite material

[0001] The present invention relates to a porous silica-clay composite material, a water purifying agent containing the porous silica-clay composite material, a soil powder containing the porous silica-clay composite material, and a method for producing the porous silica-clay composite material.

[0002] Porous silica is known to be used to adsorb gases, water, etc. To improve the adsorption performance of porous silica, it is necessary to increase the specific surface area, but there is a limit to how much this can be achieved.

[0003] Japanese Patent Application Laid-Open No. 2008-137859

[0004] In one aspect of the present invention, the content of the clay material relative to the sum of the clay material and silica, [[clay material / (clay material+silica)]×100], is 1 to 10% by weight, and the specific surface area is 1080 m ２ / g or more.

[0005] Another aspect of the present invention is a water purification agent comprising the porous silica-clay composite material described above.

[0006] Another aspect of the present invention is a soil powder containing the porous silica-clay composite material described above.

[0007] Another aspect of the present invention is a method for producing a porous silica-clay composite material, comprising: i) a mixing step of mixing a first solution containing a clay material, a base, and water with a second solution containing a silica source, an acid, water, and optionally a clay material; and ii) a drying step of heating and drying the mixed solution mixed in the mixing step, wherein the ratio of the sum of the weight of the clay material and the weight of the base contained in the mixed solution to the sum of the weight of the silica source and the acid [(weight of silica source + weight of acid) / (weight of clay material + weight of base)] is 52 to 300.

[0008] FIG. 1 is a schematic diagram showing an example of a method for producing a porous silica-clay composite material according to the present invention.

[0009] An embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described below. The present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be practiced with appropriate modifications within the scope of its gist.

[0010] <Porous silica-clay composite material>

[0011] The porous silica-clay composite material according to this embodiment has a clay material content of 1 to 10% by weight relative to the sum of the clay material and silica [[clay material / (clay material+silica)]×100], and a specific surface area of ​​1080 m ２ / g or more.

[0012] First, the components of the porous silica-clay composite material according to this embodiment will be described.

[0013] The clay material (Clay) is a natural or artificial swelling clay mineral. Examples of swelling clay minerals include bentonite, saponite, stevensite, and hectorite. These clay materials may be contained alone or in combination. In this specification, the clay material refers to a clay material in a dry state that does not contain moisture.

[0014] Silica is, for example, a silicon compound such as silicon dioxide, which is a hydrolysis product of alkoxysilane. Examples of alkoxysilanes that serve as silica sources include tetramethoxysilane, tetraethoxysilane, trimethylmethoxysilane, dimethyldimethoxysilane, diethylethoxysilane, hydroxyethyltrimethoxysilane, hydroxyethyldimethylmethoxysilane, 3-aminopropyldimethylmethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 2-methoxyethyltriethoxysilane, phenyltriethoxysilane, p-hydroxyphenyltrimethoxysilane, p-hydroxybenzyltriethoxysilane, and p-mercaptobenzyltripropoxysilane, with tetramethoxysilane and tetraethoxysilane being preferred. Water glass can also be used as the silica source.

[0015] Generally, clay minerals are composed of negatively charged tetrahedrons of SiO ４ octahedral AlO nanosheets with negative charges between them ６ or MgO ６ The basic structure is composed of three nanosheets sandwiched between two nanosheets, and multiple layers of this basic structure are stacked on top of each other. Exchangeable cations such as potassium ions exist between each layer, and the layers are electrostatically bonded to each other by these cations. However, because the bonds between the layers are weak, they easily swell and peel off in water. However, when silica and clay materials are mixed, the silica infiltrates between the layers in the clay mineral, allowing the three-dimensional structure of the clay mineral to be maintained through the silica.

[0016] The content of the clay material relative to the silica is 1 to 10% by weight. If this content is too high, the clay material cannot be mixed uniformly in the sample, and if this content is too low, it becomes difficult to increase the specific surface area. From this perspective, the lower limit of this content is preferably 1.1%, more preferably 1.2%, and even more preferably 1.25%. The upper limit of this content is preferably 9%, more preferably 8%, and even more preferably 7%.

[0017] In addition, appropriate amounts of known components such as colorants, decolorizing agents, deodorizing agents, viscosity adjusters, pH adjusters, fertilizer components, etc. may be added depending on the intended use. In addition to the above components, other components may also be added within a range in which the effects of the porous silica-clay composite material according to this embodiment can be obtained.

[0018] Next, the physical properties of the porous silica-clay composite material according to this embodiment will be described.

[0019] The specific surface area of ​​the porous silica-clay composite material according to this embodiment is 1080 m ２ The lower limit of the specific surface area is preferably 1100 m ２ / g, more preferably 1150m ２ / g, more preferably 1200m ２ The upper limit of the specific surface area is, for example, 2000 m ２ / g, and 1950m２ / g. Such a high specific surface area allows for high adsorption and water retention.

[0020] The pore size of the porous silica-clay composite material according to this embodiment is 2 to 30 nm. The lower limit of the pore size is preferably 2.5 nm, more preferably 3 nm, and even more preferably 3.5 nm. The upper limit of the pore size is preferably 20 nm, more preferably 15 nm. By setting the pore size within this range, it becomes possible to adsorb a variety of molecules into the pores and absorb liquids by capillary condensation.

[0021] The cation exchange capacity (CEC) of the porous silica-clay composite material according to this embodiment is 10 meq / 100g or more. The lower limit of the CEC is preferably 15 meq / 100g, more preferably 16 meq / 100g, and even more preferably 17 meq / 100g. The upper limit of the CEC is, for example, 120 meq / 100g, preferably 110 meq / 100g. By having such a high CEC, the occlusion and sustained release performance of cationic substances can be improved.

[0022] The water absorption rate of the porous silica-clay composite material according to this embodiment is 50% or more. The lower limit of the water absorption rate is preferably 55%, more preferably 60%, and even more preferably 65%. The upper limit of the water absorption rate may be, for example, 410% or 400%. Such a high water absorption rate enables high water retention.

[0023] The methylene blue adsorption rate of the porous silica-clay composite material according to this embodiment is 60% or more. The lower limit of the methylene blue adsorption rate is preferably 70%, more preferably 80%, and even more preferably 85%. The upper limit of the methylene blue adsorption rate may be, for example, 99.6% or even 99%. Such a high methylene blue adsorption rate enables high adsorption properties.

[0024] The total pore volume of the porous silica-clay composite material according to this embodiment is 0.7 cm ３The lower limit of the total pore volume is preferably 0.8 cm ３ / g, more preferably 1 cm ３ / g, and more preferably 1.5 cm ３ The upper limit of the total pore volume is, for example, 4.1 cm ３ / g, and 3 cm ３ / g. Such a high total pore volume allows for high water retention and adsorption.

[0025] <Applications of porous silica-clay composite materials>

[0026] The water purifying agent according to this embodiment includes the porous silica-clay composite material described above. Because such a water purifying agent has high adsorption properties, when mixed with unpurified water such as muddy water, it can adsorb and remove impurities.

[0027] The soil powder according to this embodiment contains the porous silica-clay composite material described above. Because this type of soil powder has high water retention, it can retain even small amounts of rainwater, making it possible to cultivate plants in dry regions with little rain or on the rooftops of buildings. Furthermore, if fertilizer components such as phosphoric acid are used as raw materials, it can also serve as nutrients for the soil.

[0028] In addition to the above applications, it can also be used as a deodorizer, desiccant, gardening sponge, pet litter, wall material, water-retentive road pavement, water purification agent, soil purification agent, exhaust gas treatment, oil adsorbent, recovery of rare earths and radioactive materials, food additive, heat insulation material, soundproofing material, heat-resistant material, humidity conditioner, drug delivery carrier, etc.

[0029] <Method of manufacturing porous silica-clay composite material>

[0030] As shown in FIG. 1 , the method for producing a porous silica-clay composite material according to this embodiment includes: i) a mixing step of mixing a first solution containing a clay material, a base, and water with a second solution containing a silica source, an acid, water, and optionally a clay material; and ii) a drying step of heating and drying the mixed solution obtained in the mixing step.

[0031] i) Mixing Step In the mixing step, first, a first solution containing a clay material, a base, and water and a second solution containing a silica source, an acid, water, and optionally a clay material are prepared. Then, the basic first solution and the acidic second solution are mixed. The base contained in the first solution is preferably added to the first solution immediately before the first solution and the second solution are mixed.

[0032] The clay material is a natural or artificial swelling clay mineral, such as bentonite, saponite, stevensite, or hectorite. These clay materials may be contained alone or in combination. It is preferable to use a clay material in a dry state that does not contain moisture.

[0033] The clay material is introduced into the mixed solution at a content of 0.1 to 10% by weight. The lower limit of the clay material content in the mixed solution is preferably 0.11%, more preferably 0.12%, and even more preferably 0.13%. The upper limit of the clay material content in the mixed solution is preferably 9%, more preferably 8%, and even more preferably 7%. The clay material may be introduced entirely into only the first solution, or may be introduced in divided amounts into the first solution and the second solution.

[0034] Water is introduced into the first solution and the second solution in an amount of 20 to 95% by weight based on the mixed solution. The lower limit of the water content in the mixed solution is preferably 30%, more preferably 40%, and even more preferably 50%. The upper limit of the water content in the mixed solution is preferably 90%, more preferably 85%, and even more preferably 80%.

[0035] The base is introduced into the first solution to increase the porosity of the silica, and is preferably introduced in the form of an aqueous solution.

[0036] The base may be an alkylamine such as methylamine, ethylamine, dimethylamine, diethylamine, trimethylamine, or triethylamine, or ammonia, sodium hydroxide, or potassium hydroxide, preferably ammonia. The base is introduced into the first solution at a content of 0.05 to 0.3% by weight. The lower limit of the base content in the first solution is preferably 0.06%, more preferably 0.07%, and even more preferably 0.08%. The upper limit of the base content in the first solution is preferably 0.2%, more preferably 0.15%, and even more preferably 0.1%.

[0037] The base is preferably added after the clay material has been added to the water, and the stirring step is preferably carried out before the base is added, i.e., after the clay material has been added to the water.

[0038] The stirring in the stirring step is carried out for 1 to 72 hours. The lower limit of the stirring time is preferably 2 hours, more preferably 3 hours, and even more preferably 4 hours. The upper limit of the heating time is preferably 70 hours, more preferably 50 hours, and even more preferably 30 hours. The stirring can be carried out at room temperature.

[0039] The silica source is introduced into the second solution at a content of 30 to 90% by weight. The lower limit of the silica source content in the second solution is preferably 40%, more preferably 45%, and even more preferably 50%. The upper limit of the silica source content in the second solution is preferably 85%, more preferably 80%, and even more preferably 78%.

[0040] The silica source is an alkoxysilane, such as tetramethoxysilane, tetraethoxysilane, trimethylmethoxysilane, dimethyldimethoxysilane, diethylethoxysilane, hydroxyethyltrimethoxysilane, hydroxyethyldimethylmethoxysilane, 3-aminopropyldimethylmethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 2-methoxyethyltriethoxysilane, phenyltriethoxysilane, p-hydroxyphenyltrimethoxysilane, p-hydroxybenzyltriethoxysilane, p-mercaptobenzyltripropoxysilane, etc., with tetramethoxysilane and tetraethoxysilane being preferred. These silica sources may be used alone or in combination.

[0041] The acid is introduced into the second solution as a catalyst for hydrolyzing the silica source, and is preferably introduced in the form of an aqueous solution.

[0042] The acid may be hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, oxalic acid, carbonic acid, or the like, and is preferably phosphoric acid. The acid is introduced into the second solution at a content of 0.03 to 0.2% by weight. The lower limit of the acid content in the second solution is preferably 0.04%, more preferably 0.05%, and even more preferably 0.06%. The upper limit of the acid content in the second solution is preferably 0.19%, more preferably 0.18%, and even more preferably 0.17%.

[0043] The ratio of the weight of the silica source and the weight of the acid to the weight of the clay material and the weight of the base contained in the mixed solution [(weight of silica source + weight of acid) / (weight of clay material + weight of base)] is 52 to 300. The lower limit of this value is preferably 53, more preferably 54, and even more preferably 55. The upper limit of this value is preferably 290, more preferably 280, and even more preferably 270. By setting the value within these ranges, a high specific surface area can be achieved.

[0044] After mixing, the mixture may be left as is to allow aging to occur. The aging temperature is 20 to 100°C. The lower limit of the aging temperature is preferably 21°C, more preferably 22°C, and even more preferably 23°C. The upper limit of the aging temperature is preferably 90°C, more preferably 80°C, and even more preferably 70°C. The aging time is 1 to 72 hours. The lower limit of the aging time is preferably 2 hours, more preferably 3 hours, and even more preferably 4 hours. The upper limit of the aging time is preferably 70 hours, more preferably 50 hours, and even more preferably 30 hours.

[0045] ii) Drying Step The drying temperature in the drying step is 20 to 100°C. The lower limit of the drying temperature is preferably 23°C, more preferably 30°C, and even more preferably 40°C. The upper limit of the drying temperature is preferably 100°C, more preferably 90°C, and even more preferably 80°C.

[0046] The drying time in the drying step is 5 to 168 hours. The lower limit of the drying time is preferably 6 hours, more preferably 7 hours, and even more preferably 8 hours. The upper limit of the drying time is preferably 160 hours, more preferably 150 hours, and even more preferably 140 hours.

[0047] After drying, the resulting dried product can be pulverized to obtain a powder of the porous silica-clay composite material.

[0048] Next, examples of the present invention and comparative examples will be described, but the present invention is not limited to these.

[0049] <Production of porous silica-clay composite material>

[0050] A basic first solution containing the components shown in Table 1 below and an acidic second solution containing the components shown in Table 2 were prepared. The first and second solutions were then mixed at room temperature for 1 minute until homogeneous, and then aged at 70°C for 1 day. The mixture was then dried at 70°C for 1 day, and the dried product was pulverized to obtain a powder of a porous silica-clay composite material. Tetraethoxysilane was manufactured by Tokyo Chemical Industry Co., Ltd., and bentonite, saponite, hectorite, and stevensite were manufactured by Kunimine Kogyo Co., Ltd.

[0051] <Physical property evaluation>

[0052] Measurement of the content of clay material relative to silica (Clay in product: wt%) (total clay material weight) / (total clay material weight + SiO obtained from added TEOS) ２ The calculation was made by multiplying the weight by 100.

[0053] Specific surface area, pore size, total pore volume measurement N ２ A gas adsorption test was carried out, and the specific surface area, pore size, and total pore volume were calculated by the BET method.

[0054] Cation exchange capacity (CEC) measurement: The sample was subjected to cation exchange three times with ammonium acetate, washed three times with alcohol, and extracted with KCl three times. The extract was then filtered through filter paper. The amount of ammonium ions in the extract was determined using the formol method, and the cation exchange capacity per 100 g of sample was calculated.

[0055] Measurement of water absorption rate Seven holes of approximately 2 mm were made in the bottom of a metal container and a glass fiber filter was placed inside. Water was placed in a metal tray and the container was left to stand for 60 minutes, after which the weight was measured. A 3 g sample was placed inside and left to stand for 60 minutes, after which the weight was measured. The water absorption rate was calculated by (weight of sample after water absorption - weight of sample without sample after water absorption - sample weight) / sample weight x 100.

[0056] Measurement of methylene blue adsorption: 0.1 g of sample was added to 100 mL of 0.05 mM methylene blue aqueous solution and stirred for 1 day. The sample was filtered through a PTFE syringe filter and the absorbance was measured. The amount of methylene blue adsorbed was calculated from the reduction rate relative to the blank absorbance.

[0057] Table 1 shows the composition of the basic solution (first solution), Table 2 shows the composition of the acidic solution (second solution), and Table 3 shows the composition of the mixed solution of the first and second solutions in each example and comparative example. Table 4 shows the physical properties of the product in each example and comparative example. Note that tetraethoxysilane (TEOS) was used as the alkoxysilane in both the examples and comparative examples.

[0058]

[0059]

[0060]

[0061]

[0062] From the above, it was confirmed that the porous silica-clay composite materials of each Example had a high specific surface area, CEC, water absorption rate, methylene blue adsorption rate, and total pore volume.

Claims

1. by weight, the content ratio of the clay material to the sum of the clay material and silica [[[clay material / (clay material + silica)] × 100]] is 1 to 10%, A porous silica-clay composite material having a specific surface area of 1080 m ２ / g or more.

2. A water purifying agent containing the porous silica-clay composite material according to Claim 1.

3. A powder for soil containing the porous silica-clay composite material according to Claim 1.

4. i) A mixing step of mixing a first solution containing a clay material, a base, and water, a silica source, an acid, water, and optionally the clay material to form a second solution; ii) A drying step of heating and drying the mixed solution mixed in the mixing step, wherein the sum of the weight of the silica source and the weight of the acid to the sum of the weight of the clay material and the weight of the base contained in the mixed solution [(weight of silica source + weight of acid) / (weight of clay material + weight of base)] is 52 to 300, a method for producing a porous silica-clay composite material.

5. The method for producing a porous silica-clay composite material according to Claim 4, wherein the clay material is a swelling clay mineral.

6. The method for producing a porous silica-clay composite material according to Claim 5, wherein the swelling clay mineral is any one or more selected from bentonite, saponite, stevensite, and hectorite.

7. The content ratio of the clay material to the mixed solution is 0.1 to 10% by weight, the method for producing a porous silica-clay composite material according to any one of Claims 4 to 6.

8. The method for producing a porous silica-clay composite material according to any one of Claims 4 to 6, wherein the base is ammonia.

9. The content ratio of the base to the first solution is 0.05 to 0.3% by weight, the method for producing a porous silica-clay composite material according to any one of Claims 4 to 6.

10. The method for producing a porous silica-clay composite material according to any one of Claims 4 to 6, wherein the silica source is an alkoxysilane.

11. The content ratio of the silica source to the second solution is 30 to 90% by weight, the method for producing a porous silica-clay composite material according to any one of Claims 4 to 6.

12. The method for producing a porous silica-clay composite material according to any one of Claims 4 to 6, wherein the acid is phosphoric acid.

13. The content ratio of the acid to the second solution is 0.03 to 0.2% by weight, the method for producing a porous silica-clay composite material according to any one of Claims 4 to 6.

14. In the mixing step, the first solution is prepared by adding the base after mixing the clay material and the water, and a stirring step of stirring the clay material and the water is performed before adding the base. The method for producing a porous silica-clay composite material according to any one of claims 4 to 6.

15. The method for producing a porous silica-clay composite material according to claim 14, wherein the stirring time in the stirring step is 1 to 72 hours.

16. The method for producing a porous silica-clay composite material according to any one of claims 4 to 6, wherein the heating temperature in the drying step is 20 to 100 °C.

17. The method for producing a porous silica-clay composite material according to any one of claims 4 to 6, wherein the drying time in the drying step is 5 to 168 hours.