Composite metal oxides

Abstract

The present invention provides a composite metal oxide that has exceptional anion adsorptivity and is capable of removing multiple types of anions, each at a high adsorption rate.　The present disclosure is a composite metal oxide represented by formula (1). The composite metal oxide has a solid base amount of 3.70 mmol / g.　Formula (1): (Mg1−xAlx)O1+x / 2 [In formula (1), x is a number that satisfies 0.18≤x≤0.45.]

Description

[Technical Field]

[0001] This invention relates to a composite metal oxide used in water treatment and the like. [Background technology]

[0002] Water treatment technologies are primarily developed for the purpose of treating drinking water, sewage, or wastewater, and are mainly divided into biological treatment and physicochemical treatment. Biological treatment is a method of decomposing pollutants through the action of microorganisms. On the other hand, physicochemical treatment differs depending on the state in which the pollutants are contained in the water.

[0003] For example, if the pollutant is a suspended solid or colloidal substance, it is usually separated and removed by sedimentation and filtration. However, if the pollutant is a fine suspended solid or colloidal substance that cannot be separated and removed, it is immobilized with a coagulant and then separated and removed.

[0004] Furthermore, when pollutants are dissolved substances contained in drinking water or factory wastewater, they are removed by means such as electrodialysis, reverse osmosis, evaporation, ion exchange, or adsorption. However, electrodialysis, reverse osmosis, and evaporation require significant equipment costs and are limited to specific locations. While ion exchange using ion exchange resins can be implemented with relatively inexpensive equipment, the use of highly concentrated alkaline aqueous solutions in the regeneration process results in high regeneration costs. For these reasons, adsorption methods, which can remove pollutants from water with relatively inexpensive equipment and processing costs, are attracting attention.

[0005] As an example of a water treatment method using adsorption, Patent Document 1 discloses a method for treating wastewater containing anions such as chloride ions, in which a composite metal oxide represented by a specific chemical formula and having a rock salt-type structure is brought into contact with the wastewater, thereby fixing the anions to the composite metal oxide.

[0006] Furthermore, Non-Patent Document 1 discloses a water purification method that removes various anions such as phosphate ions and chloride ions from water using hydrotalcite (HT) or magnesium-aluminum oxide (Mg-Al oxide). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2002-136965 [Non-patent literature]

[0008] [Non-Patent Document 1] Tomohito Kameda, Toshiaki Yoshioka, Yoshiaki Umezu, and Akitsugu Okuwaki, "Application of Hydrotalcite to Water Environment Conservation and Purification," The Chemical Times 2005 No.1 (Issue No. 195), pp. 10-16. [Overview of the project] [Problems that the invention aims to solve]

[0009] Drinking water and industrial wastewater may contain multiple types of anions. However, with conventional composite metal oxides, it is practically difficult to remove multiple types of anions simultaneously with high removal rates, which sometimes necessitates multiple water treatment processes.

[0010] Therefore, the present invention aims to provide a composite metal oxide with excellent anion adsorption properties that can remove multiple types of anions with high adsorption rates. [Means for solving the problem]

[0011] As a result of intensive studies to achieve the above object, the inventors of the present invention have found that by using a specific composite metal oxide represented by the following formula (1) and having a high solid base amount, at least four types of anions can be removed with high adsorption rates respectively. The present disclosure has been completed based on such findings and includes the following aspects.

[0012] (First Disclosure)[[ID=?]] The first disclosure is a composite metal oxide represented by the following formula (1). This composite metal oxide has a solid base amount of 3.70 mmol / g or more. (Mg 1-x Al x )O 1+x / 2 ···(1) [[ID=?]][In formula (1), x is a number satisfying 0.18 ≦ x ≦ 0.45.]

[0013] (Second Disclosure) The second disclosure is, in the first disclosure above, the BET specific surface area is 150 m 2 / g to 350 m 2 / g.

[0014] (Third Disclosure) The third disclosure is a mixture containing the composite metal oxide of the first disclosure or the second disclosure and a layered double hydroxide.

[0015] (Fourth Disclosure) The fourth disclosure is, in the third disclosure above, the layered double hydroxide is a layered double hydroxide represented by the following formula (): [Mg 1-x Al x (OH)2] x+ [(A n- ) x / n ·mH2O]···(2) [In formula (2), A n- represents an anion selected from the group consisting of CO3 2- and OH - , n represents 1 or 2, x is a number satisfying 0.18 ≦ x ≦ 0.45, and m is a number satisfying 0 ≦ m < 1.] Note: There seems to be an error in the original text where the formula number in "The fourth disclosure is, in the third disclosure above, the layered double hydroxide is a layered double hydroxide represented by the following formula (): " is missing. It should probably be something like "(3)" instead of "()". Also, the "?" added in the translation for the missing formula number in the "In formula (1), x is a number satisfying 0.18 ≦ x ≦ 0.45." part is just a placeholder to show where the correct numbering should be inserted.

[0016] (Fifth Disclosure) The fifth disclosure is that, in the third or fourth disclosure above, the mixing ratio of the composite metal oxide and the layered double hydroxide is within the range of 99.99:0.01 to 50:50 by mass ratio.

[0017] (Disclosure 6) The sixth disclosure is an adsorbent comprising the composite metal oxide of the first or second disclosure described above.

[0018] (Disclosure No. 7) The seventh disclosure is a method for treating a liquid, comprising contacting the liquid with a composite metal oxide of the first or second disclosure.

[0019] (Disclosure No. 8) The eighth disclosure is an adsorbent comprising a mixture of any of the third through fifth disclosures described above.

[0020] (Disclosure 9) The ninth disclosure is a method for processing a liquid, comprising contacting the liquid with a mixture of any of the third through fifth disclosures.

[0021] (Disclosure No. 10) The tenth disclosure is a method for treating a liquid, comprising contacting the liquid with the adsorbent of the sixth disclosure. [Effects of the Invention]

[0022] The composite metal oxide of the present invention can remove at least four types of anions with high adsorption rates. Furthermore, the composite metal oxide of the present invention can efficiently adsorb and remove not only monatomic anions, but also polyatomic oxoanions and transition metal oxoanions. [Modes for carrying out the invention]

[0023] Preferred embodiments of the composite metal oxide of the present invention will be described in detail below. In this specification, unless otherwise specified, various numerical ranges refer to the range including their upper and lower limits.

[0024] [Composite metal oxides] In one embodiment of the present invention, the composite metal oxide is a composite metal oxide represented by the following formula (1). Furthermore, this composite metal oxide has a solid base content of 3.70 mmol / g or more. (Mg 1-x Al x )O 1+x / 2 ...(1) [In equation (1), x is a number that satisfies 0.18 ≤ x ≤ 0.45.]

[0025] The above-mentioned composite metal oxide can be obtained, for example, by calcining a hydrotalcite compound under predetermined conditions. Specifically, when a hydrotalcite compound is calcined under predetermined conditions, carbonate ions present between the layers of the hydrotalcite compound, along with hydroxyl groups bonded to crystal water and metal ions, are released, and the above-mentioned composite metal oxide is produced.

[0026] Hydrotalcite compounds, which are raw materials for complex metal oxides, can be synthesized, for example, as follows: First, a slurry is obtained by reacting a mixed aqueous solution of magnesium salt and aluminum salt with an alkaline substance. The obtained slurry may be subjected to hydrothermal treatment to promote crystal growth. Subsequently, the slurry is separated into solid and liquid phases, and the hydrotalcite compound powder can be obtained through washing, drying, and grinding steps.

[0027] The magnesium salts used in the synthesis of hydrotalcite compounds are not particularly limited, but examples include magnesium chloride, magnesium nitrate, magnesium sulfate, and magnesium hydroxide. Among these, it is preferable to use at least one of magnesium sulfate and magnesium chloride. These magnesium salts have the advantage of being cost-effective and readily available.

[0028] The aluminum salts used in the synthesis of hydrotalcite compounds are not particularly limited, but examples include aluminum chloride, aluminum nitrate, aluminum sulfate, and sodium aluminate. The molar ratio of Mg / Al2 in the mixed aqueous solution of magnesium salt and aluminum salt is preferably in the range of 2 to 10, and more preferably in the range of 4 to 8.

[0029] The alkaline substances used in the synthesis of hydrotalcite compounds are not particularly limited, but examples include aqueous solutions of caustic soda, ammonia, potassium hydroxide, and sodium carbonate.

[0030] Composite metal oxides obtained from such hydrotalcite compounds can easily reconstruct a hydrotalcite-like structure by incorporating ions and moisture from the atmosphere. Furthermore, because these composite metal oxides are positively charged, they readily adsorb anions such as fluoride ions and chloride ions. When the composite metal oxides incorporate moisture from the atmosphere and change into hydroxides, they can incorporate anions between their layers (i.e., intercalate).

[0031] Furthermore, the composite metal oxide of this embodiment has a solid base content of 3.70 mmol / g or more. The composite metal oxide of this embodiment, represented by formula (1) above and having the above-mentioned specific solid base content, can remove at least four types of anions with high adsorption rates. Specifically, the composite metal oxide of this embodiment can remove anions containing the elements fluorine, boron, chromium, and phosphorus with high adsorption rates. Moreover, this composite metal oxide can efficiently adsorb and remove not only monatomic anions but also polyatomic oxoanions and transition metal oxoanions. As a result, the composite metal oxide of this embodiment can greatly contribute to water purification, and therefore has the advantage of contributing to the achievement of the SDGs (Sustainable Development Goals) adopted at the UN Summit.

[0032] The upper limit of the solid base content of the composite metal oxide is not particularly limited, but is, for example, 20 mmol / g, and preferably 10 mmol / g. Specific methods for measuring the solid base content will be described later.

[0033] The amount of solid base in a composite metal oxide can be controlled by appropriately adjusting the thermal history during the manufacturing of the composite metal oxide. Specific examples of thermal history include firing conditions such as the heating time, holding temperature, holding time, and cooling time when firing hydrotalcite compounds. Generally, the firing of hydrotalcite compounds involves a series of steps: heating from room temperature, holding at a certain temperature for a certain period, cooling down, and returning to room temperature.

[0034] In this specification, the meanings of the terms relating to the calcination of hydrotalcite compounds (samples) are as follows: Heating time: This refers to the time it takes to heat a sample from room temperature to reach the desired maximum temperature when firing it in an electric furnace. Holding temperature: This refers to the maximum temperature reached when firing a sample in an electric furnace. It is also called the firing temperature. Holding time: This refers to the time the holding temperature is maintained when firing a sample in an electric furnace. Cooling time: This refers to the time it takes for a sample to cool from its holding temperature to room temperature after the holding time has elapsed when firing a sample in an electric furnace. Cooling includes not only active cooling using cooling means, but also gradual cooling such as air cooling.

[0035] The calcination conditions for producing complex metal oxides from hydrotalcite compounds are not particularly limited, as long as a solid base within the specified range described above can be obtained. For example, the heating time is preferably 0.5 to 8 hours, and more preferably 0.5 to 6 hours. Similarly, the holding temperature is preferably 350°C to 900°C, and more preferably 400°C to 850°C. Furthermore, the holding time is preferably 0 to 18 hours, and more preferably 0 to 15 hours. Also, the cooling time is preferably 0.5 to 4 hours, and more preferably 0.8 to 3 hours.

[0036] The composite metal oxide of the present invention has a BET specific surface area of ​​150 m². 2 / g~350m 2 It is preferable that the BET specific surface area is within the range of / g. When the BET specific surface area is within this range, high adsorption to multiple types of anions can be more reliably achieved.

[0037] In this specification, BET specific surface area refers to the specific surface area of ​​particulate composite metal oxides obtained by the BET method. The specific measurement method for BET specific surface area will be described later.

[0038] The BET specific surface area of ​​the composite metal oxide is 150 m². 2 / g~300m 2 A range within / g is more preferable, 155m 2 / g~260m 2 A range within / g is even more preferable.

[0039] The composite metal oxide of the present invention can be suitably used as an adsorbent for removing multiple types of anions contained in water, such as drinking water or industrial wastewater. In this case, the adsorbent may contain only the composite metal oxide of the present invention or other components, as long as it contains the composite metal oxide of the present invention. For example, a mixture containing the composite metal oxide of the present invention and a layered double hydroxide may be used as an adsorbent. That is, one aspect of the present invention is a mixture containing the composite metal oxide of the present invention and a layered double hydroxide. Since layered double hydroxides have a low bulk, a mixture containing the composite metal oxide and a layered double hydroxide has a lower bulk than an adsorbent consisting only of the composite metal oxide. Therefore, such a mixture has good handling properties when actually used as an adsorbent.

[0040] The layered double hydroxide in the above mixture is not particularly limited, but examples include the double hydroxide represented by the following formula (2). [Mg 1-x Al x (OH)2] x+ [(A n- ) x / n·mH2O]···(2) [In equation (2), A n- CO3 2- and OH - This represents an anion selected from the group consisting of the following: n is 1 or 2, x is a number satisfying 0.18 ≤ x ≤ 0.45, and m is a number satisfying 0 ≤ m < 1.

[0041] Furthermore, the layered double hydroxide represented by formula (2) above is not particularly limited, but examples include hydrotalcite compounds that serve as raw materials for composite metal oxides, and hygroscopic materials of composite metal oxides. These layered double hydroxides have the advantage of being able to reduce material costs and being readily available.

[0042] In the above mixture, the mixing ratio of the composite metal oxide and the layered double hydroxide is not particularly limited as long as it does not hinder the effects of the present invention, but it is preferable that the mass ratio of the composite metal oxide to the layered double hydroxide is in the range of 99.99:0.01 to 50:50. When the mixing ratio is within this range, it is possible to more reliably obtain good handling properties when used as an adsorbent while maintaining high adsorption properties for multiple types of anions.

[0043] [Processing method] The composite metal oxide of the present invention can also be used as an adsorbent to remove multiple types of anions contained in liquids other than water or in gases. However, in order to remove multiple types of anions with high adsorption rates, the composite metal oxide of the present invention is preferably used as an adsorbent for liquids containing water or other liquids.

[0044] Therefore, one aspect of the present invention is a method for treating a liquid, comprising contacting a liquid containing water or a liquid other than water with the composite metal oxide of the present invention. According to such a method for treating a liquid, multiple types of anions can be removed from the liquid with high adsorption rates.

[0045] Furthermore, the composite metal oxide of the present invention may be used as an adsorbent for liquids containing water or other liquids in the form of a mixture with the above-mentioned layered double hydroxide. Accordingly, another aspect of the present invention is a method for treating a liquid, which includes contacting a liquid containing water or other liquid with a mixture of the composite metal oxide of the present invention and the above-mentioned layered double hydroxide.

[0046] The composite metal oxide of the present invention can be molded according to the appropriate application. In other words, one aspect of the present invention is a molded body of the composite metal oxide of the present invention. Specifically, the molded body can be obtained by granulating or molding powdered composite metal oxide into a shape suitable for adsorption treatment. Examples of shapes for the molded body include spherical, substantially spherical, cylindrical, granular, pelletized, and tablet-shaped forms.

[0047] The granulation method or molding method used to manufacture the molded article is not particularly limited, but known methods of dry granulation or wet granulation can be used. Examples of dry granulation methods include the dry roller compactor method and the roll granulator method. Examples of wet granulation methods include the spray drying method, fluidized bed granulation method, rolling granulation method, agitation granulation method, and extrusion granulation method. The molded article containing the composite metal oxide of the present invention allows for control of the permeability of the liquid or gas containing the adsorbent and the adsorption effect during the adsorption operation.

[0048] Furthermore, the composite metal oxide of the present invention can be granulated or molded by blending it with various known additives. In other words, one aspect of the present invention is an additive-containing molded article. Examples of additives include fibers, resins, and clay minerals. Examples of fibers include chemical fibers, regenerated fibers, and natural fibers. Further examples of natural fibers include cellulose. Examples of clay minerals include bentonite, sepiolite, and kaolin. The additive-containing molded article containing the composite metal oxide of the present invention can control the strength and porosity of the molded article, and consequently, its adsorption performance.

[0049] The composite metal oxide of the present invention can be applied to a variety of uses, such as those listed below.

[0050] One aspect of the present invention is a liquid purifying material. A specific example of a liquid purifying material is a liquid purifying material comprising a composite metal oxide of the present invention and a bag having pores of a size that the composite metal oxide cannot pass through, and containing the composite metal oxide. The material of the bag may be, for example, nonwoven fabric. A liquid purifying material containing the composite metal oxide of the present invention makes it easy to separate the liquid and the liquid purifying material after they have been brought into contact.

[0051] One aspect of the present invention is a filtration device. Specific examples of filtration devices include a filtration device in which the powder and / or molded body of the composite metal oxide of the present invention is packed inside a tubular body or as a filter bed. A more specific example is a packed column in which the composite metal oxide of the present invention is packed into the column body.

[0052] One aspect of the present invention is a composite fiber. Specific examples of composite fibers include composite fibers in which the composite metal oxide of the present invention is supported on a fiber. Examples of fibers include at least one fiber selected from chemical fibers, regenerated fibers, and natural fibers. Furthermore, examples of natural fibers include cellulose. The means of supporting the composite metal oxide on the fiber are not particularly limited; the composite metal oxide may be kneaded into the fiber during the manufacturing of the fiber, or the composite metal oxide may be attached to the fiber surface using a treatment agent or the like.

[0053] Furthermore, the composite metal oxide of the present invention can also be used as a resin stabilizer. In other words, one aspect of the present invention is a resin composition containing the composite metal oxide of the present invention. Since the composite metal oxide of the present invention is obtained by calcining hydrotalcite compounds to remove interlayer water, less moisture is generated when it is blended into a resin and heated. As a result, the resin composition containing the composite metal oxide of the present invention can suppress foaming during heat processing compared to a resin composition containing hydrotalcite compounds.

[0054] Furthermore, the present invention is not limited to the embodiments described above or the examples described later, and can be appropriately combined, substituted, or modified without departing from the purpose and spirit of the present invention. [Examples]

[0055] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0056] The various measurement methods for the examples are as follows.

[0057] <Molar ratio (MgO / Al2O3)> The molar ratio was measured using the acid dissolution method described below. However, for samples that did not dissolve using the acid dissolution method, the molar ratio was measured using the alkali fusion method described later.

[0058] (Acid dissolution method) 0.5 g of the sample was placed in a 100 mL beaker, 10 mL of dilute hydrochloric acid and 5 mL of perchloric acid were added, and the sample was heated on a hot plate to dissolve it. The sample solution in the beaker was transferred to a 250 mL volumetric flask and diluted to 250 mL. Using this diluted sample solution, the MgO content and Al2O3 content were quantified as follows. (1) Determination of MgO Using a volumetric pipette, 10 mL of the above sample solution was transferred to a 200 mL beaker and diluted to 100 mL with deionized water. 5 mL of triethanolamine aqueous solution was added to this diluted sample solution, and ammonium chloride ammonia buffer was added dropwise until the pH reached 10 using a pH meter. Fifteen drops of Universal BT reagent were added as an indicator, and the mixture was titrated with 0.01 mol / L EDTA standard solution. (2) Determination of Al2O3 Using a volumetric pipette, 10 mL of the above sample solution was placed in a 200 mL beaker, and 30 mL of 0.01 mol / L - CyDTA standard solution was added using a volumetric pipette. Hexamethylenetetramine was added using a pH meter to adjust the pH to 5 - 5.5. Three drops of XO test solution were added as an indicator, and it was titrated with 0.01 mol / L zinc acetate standard solution. Using the MgO content and Al2O3 content quantified as above, the molar ratio (MgO / Al2O3) was calculated.

[0059] (Alkali fusion method) 0.5 g of the sample was placed in a platinum crucible, 3 g of boric acid and 5 g of sodium carbonate were added, and it was melted at 950 °C for 2 hours in an electric furnace. The melt was transferred to a 200 mL beaker, and 100 mL of dilute hydrochloric acid was added to dissolve it. Further, this solution was transferred to a 250 mL volumetric flask and diluted to 250 mL. The quantification of the MgO content and the Al2O3 content was carried out in the same manner as in the case of the acid dissolution method, and the molar ratio was calculated.

[0060] <BET specific surface area> It was measured using the high-precision specific surface area and pore size distribution measuring device "BELSORP-max" manufactured by MicrotracBEL Corporation.

[0061] <Solid base amount> 0.2 g of the sample was placed in a conical flask with a stopper, and 5 mL of benzene (Wako Reagent Special Grade) was added. 1 mL of a 0.1 wt% benzene solution of phenolphthalein was added as an indicator with pKa = 9.3 to make the sample solution turn pink. It was titrated with 0.1 mol / L benzoic acid - benzene solution until the sample solution turned white, and the amount of benzoic acid - benzene solution required for the titration was taken as A (mL). After closing the stopper of the conical flask and leaving it standing for 24 hours, the sample solution turned pink again, so it was titrated again with 0.1 mol / L benzoic acid - benzene solution until the sample solution turned white, and the amount of benzoic acid - benzene solution required for the titration was taken as B (mL). This operation was repeated once more, and the amount of benzoic acid - benzene solution required for the titration was taken as C (mL). Based on the following formula, the solid base amount was calculated from the total of the titration amounts for three times. Solid base amount (mmol / g) = 0.1(A+B+C) / 0.2g

[0062] <Adsorption rates of various anions> The adsorption rates of multiple types of anions contained in water were measured as follows for each type and concentration of anion.

[0063] (Fluorine (F) adsorption rate when the blank concentration is 10 ppm) 0.03 g of the sample was placed in a 50 mL centrifuge tube, and 30 mL of a 10 ppm sodium fluoride aqueous solution was added. The centrifuge tube was placed in a shaker and shaken at a speed of 160 rpm for 15 hours. The centrifuge tube was placed in a centrifuge and centrifuged at 10,000 g for 5 minutes. The supernatant was filtered through a membrane filter with a pore size of 0.2 μm. 10 mL of the obtained filtrate was placed in a 20 mL volumetric flask, and 2 mL of Alfusson's reagent (2.5 g of Alfusson's reagent dissolved in 50 mL of deionized water) and 4 mL of acetone were added, and the solution was diluted to 20 mL with deionized water. After the diluted filtrate was allowed to stand in the dark for 1 hour, the fluorine concentration D (ppm) was measured at 620 nm using a Hitachi High-Tech Science Co., Ltd. spectrophotometer "U-4100", and the adsorption rate was calculated based on the following formula. Adsorption rate (%)=(10-D) / 10×100

[0064] (Fluorine (F) adsorption rate when the blank concentration is 50 ppm) 0.03 g of the sample was placed in a 50 mL centrifuge tube, and 30 mL of a 50 ppm sodium fluoride aqueous solution was added. The centrifuge tube was placed in a shaker and shaken at a speed of 160 rpm for 15 hours. The centrifuge tube was placed in a centrifuge and centrifuged at 10,000 g for 5 minutes. The supernatant was filtered through a membrane filter with a pore size of 0.2 μm. 10 mL of the obtained filtrate was placed in a 20 mL volumetric flask, and 2 mL of Alfusson's reagent (2.5 g of Alfusson's reagent dissolved in 50 mL of deionized water) and 4 mL of acetone were added, and the solution was diluted to 20 mL with deionized water. After the diluted filtrate was allowed to stand in the dark for 1 hour, the fluorine concentration E (ppm) was measured at 620 nm using a Hitachi High-Tech Science Co., Ltd. spectrophotometer "U-4100", and the adsorption rate was calculated based on the following formula. Adsorption rate (%)=(50-E) / 50×100

[0065] (Boron(B) adsorption rate when the blank concentration is 10 ppm) 0.03 g of the sample was placed in a 50 mL centrifuge tube, and 30 mL of a 10 ppm sodium tetraborate aqueous solution was added. The centrifuge tube was placed in a shaker and shaken at a speed of 160 rpm for 15 hours. The centrifuge tube was placed in a centrifugal separator and centrifuged at 10,000 g for 5 minutes. The supernatant was filtered through a membrane filter with a pore size of 0.2 μm. The boron concentration F (ppm) of the obtained filtrate was measured using an ICP emission spectrometer "SPS3500DD" manufactured by Hitachi High-Tech Science Corporation, and the adsorption rate was calculated based on the following formula. Adsorption rate (%)=(10-F) / 10×100

[0066] (Chromium (Cr) adsorption rate when the blank concentration is 80 ppm) 0.03 g of the sample was placed in a 50 mL centrifuge tube, and 30 mL of potassium chromate aqueous solution with a chromium concentration of 80 ppm was added. The centrifuge tube was placed in a shaker and shaken at a shaking speed of 160 rpm for 15 hours. The centrifuge tube was placed in a centrifuge and centrifuged at 10,000 g for 5 minutes. The supernatant was filtered through a membrane filter with a pore size of 0.2 μm. The chromium concentration G (ppm) of the obtained filtrate was measured using an ICP emission spectrometer "SPS3500DD" manufactured by Hitachi High-Tech Science Corporation, and the adsorption rate was calculated based on the following formula. Adsorption rate (%)=(80-G) / 80×100

[0067] (Chromium (Cr) adsorption rate when the blank concentration is 100 ppm) 0.03 g of the sample was placed in a 50 mL centrifuge tube, and 30 mL of potassium chromate aqueous solution with a chromium concentration of 100 ppm was added. The centrifuge tube was placed in a shaker and shaken at a shaking speed of 160 rpm for 15 hours. The centrifuge tube was placed in a centrifuge and centrifuged at 10,000 g for 5 minutes. The supernatant was filtered through a membrane filter with a pore size of 0.2 μm. The chromium concentration H (ppm) of the obtained filtrate was measured using an ICP emission spectrometer "SPS3500DD" manufactured by Hitachi High-Tech Science Corporation, and the adsorption rate was calculated based on the following formula. Adsorption rate (%)=(100-H) / 100×100

[0068] (Phosphorus (P) adsorption rate when the blank concentration is 20 ppm) 0.03 g of the sample was placed in a 50 mL centrifuge tube, and 30 mL of a 20 ppm sodium dihydrogen phosphate aqueous solution was added. The centrifuge tube was placed in a shaker and shaken at a speed of 160 rpm for 15 hours. The centrifuge tube was placed in a centrifuge and centrifuged at 10,000 g for 5 minutes. The supernatant was filtered through a membrane filter with a pore size of 0.2 μm. The phosphorus concentration I (ppm) of the obtained filtrate was measured using an ICP emission spectrometer "SPS3500DD" manufactured by Hitachi High-Tech Science Corporation, and the adsorption rate was calculated based on the following formula. Adsorption rate (%)=(20-I) / 20×100

[0069] (Phosphorus (P) adsorption rate when the blank concentration is 30 ppm) 0.03 g of the sample was placed in a 50 mL centrifuge tube, and 30 mL of a 30 ppm sodium dihydrogen phosphate aqueous solution was added. The centrifuge tube was placed in a shaker and shaken at a speed of 160 rpm for 15 hours. The centrifuge tube was placed in a centrifuge and centrifuged at 10,000 g for 5 minutes. The supernatant was filtered through a membrane filter with a pore size of 0.2 μm. The phosphorus concentration J (ppm) of the obtained filtrate was measured using an ICP emission spectrometer "SPS3500DD" manufactured by Hitachi High-Tech Science Corporation, and the adsorption rate was calculated based on the following formula. Adsorption rate (%)=(30-J) / 30×100

[0070] (Phosphorus (P) adsorption rate when the blank concentration is 40 ppm) 0.03 g of the sample was placed in a 50 mL centrifuge tube, and 30 mL of a 40 ppm sodium dihydrogen phosphate aqueous solution was added. The centrifuge tube was placed in a shaker and shaken at a speed of 160 rpm for 15 hours. The centrifuge tube was placed in a centrifuge and centrifuged at 10,000 g for 5 minutes. The supernatant was filtered through a membrane filter with a pore size of 0.2 μm. The phosphorus concentration K (ppm) of the obtained filtrate was measured using an ICP emission spectrometer "SPS3500DD" manufactured by Hitachi High-Tech Science Corporation, and the adsorption rate was calculated based on the following formula. Adsorption rate (%)=(40-K) / 40×100

[0071] Next, examples and comparative examples of the present invention will be described.

[0072] (Example 1) In a 1 L reaction vessel containing a small amount of water, 201 mL of 1.5 mol / L magnesium chloride aqueous solution, 134 mL of 1.0 mol / L aluminum chloride aqueous solution, and a mixed solution of 257 mL of 3.4 mol / L sodium hydroxide aqueous solution and 107 mL of 0.75 mol / L sodium carbonate aqueous solution were simultaneously added dropwise while stirring to obtain the reaction product. The pH during the reaction was 9.5. After washing the obtained reaction product with water, it was dried overnight at 105°C and then pulverized. The obtained powder was calcined under the conditions of heating time 1 hour, holding temperature 400°C, holding time 12 hours, and cooling time 1 hour to obtain the sample of Example 1.

[0073] (Example 2) Samples for Example 2 were obtained in the same manner as in Example 1, except that the firing conditions were: heating time of 1.25 hours, holding temperature of 500°C, holding time of 2 hours, and cooling time of 1.25 hours.

[0074] (Example 3) Sample for Example 3 was obtained in the same manner as in Example 1, except that the firing conditions were: heating time of 1.5 hours, holding temperature of 600°C, holding time of 2 hours, and cooling time of 1.75 hours.

[0075] (Example 4) Sample for Example 4 was obtained in the same manner as in Example 1, except that the firing conditions were: heating time of 1.75 hours, holding temperature of 700°C, holding time of 2 hours, and cooling time of 1.95 hours.

[0076] (Example 5) Sample for Example 5 was obtained in the same manner as in Example 1, except that the firing conditions were 2 hours of heating, 800°C, 6 hours of holding time, and 2.08 hours of cooling time.

[0077] (Example 6) Sample for Example 6 was obtained in the same manner as in Example 1, except that the firing was performed under the conditions of heating time of 2 hours, holding temperature of 800°C, holding time of 0 hours, and cooling time of 2.08 hours.

[0078] (Example 7) Sample for Example 7 was obtained in the same manner as in Example 1, except that the firing conditions were 2 hours of heating, 800°C, 2 hours of holding time, and 2.08 hours of cooling time.

[0079] (Example 8) Sample for Example 8 was obtained in the same manner as in Example 1, except that the firing conditions were: heating time 2.13 hours, holding temperature 850°C, holding time 2 hours, and cooling time 2.13 hours.

[0080] (Comparative Example 1) A sample for Comparative Example 1 was obtained in the same manner as in Example 1, except that the firing was performed under the conditions of heating time of 50 minutes, holding temperature of 350°C, holding time of 2 hours, and cooling time of 0.75 hours.

[0081] (Comparative Example 2) A sample for Comparative Example 2 was obtained in the same manner as in Example 1, except that the firing was performed under the conditions of heating time of 2.25 hours, holding temperature of 900°C, holding time of 2 hours, and cooling time of 2.2 hours.

[0082] The chemical formulas of the samples obtained in Examples 1-8 and Comparative Examples 1 and 2 as described above are all Mg 4.5 Al2O 7.5 That was the case.

[0083] For each sample in Examples 1-8 and Comparative Examples 1 and 2, the powder properties (molar ratio and BET specific surface area) and the adsorption rates of various anions (blank concentrations F: 10 ppm, B: 10 ppm, Cr: 80 ppm, P: 30 ppm) were measured. These results are shown in Table 1 below.

[0084] [Table 1]

[0085] Regarding the adsorption rates of various anions, a good adsorption rate is indicated by an adsorption rate of 90% or higher for F at 10 ppm, 90% or higher for B at 10 ppm, 90% or higher for Cr at 80 ppm, and 90% or higher for P at 30 ppm.

[0086] (Example 9) In a 1 L reaction vessel containing a small amount of water, 228 mL of a 1.5 mol / L aqueous magnesium chloride solution, 114 mL of a 1.0 mol / L aqueous aluminum chloride solution, and a mixed solution of 268 mL of a 3.4 mol / L aqueous sodium hydroxide solution and 91 mL of a 0.75 mol / L aqueous sodium carbonate solution were simultaneously added dropwise while stirring to obtain the reaction product. The pH during the reaction was 10.0. After washing the obtained reaction product with water, it was dried overnight at 105°C and then pulverized. The resulting powder was calcined under the conditions of heating time 1 hour, holding temperature 400°C, holding time 2 hours, and cooling time 4 hours to obtain the sample for Example 9.

[0087] (Example 10) Sample for Example 10 was obtained in the same manner as in Example 9, except that the firing conditions were 4 hours of heating, 400°C of holding temperature, 2 hours of holding time, and 1 hour of cooling time.

[0088] (Example 11) Sample for Example 11 was obtained in the same manner as in Example 9, except that the firing was performed under the conditions of heating time of 1 hour, holding temperature of 400°C, holding time of 2 hours, and cooling time of 1 hour.

[0089] (Example 12) Sample for Example 12 was obtained in the same manner as in Example 9, except that the firing conditions were 4 hours of heating, 400°C of holding temperature, 2 hours of holding time, and 4 hours of cooling time.

[0090] (Example 13) Sample for Example 13 was obtained in the same manner as in Example 9, except that the firing was performed under the conditions of heating time of 1 hour, holding temperature of 400°C, holding time of 12 hours, and cooling time of 1 hour.

[0091] (Example 14) Sample for Example 14 was obtained in the same manner as in Example 9, except that the firing was performed under the conditions of heating time of 1.25 hours, holding temperature of 500°C, holding time of 2 hours, and cooling time of 1.25 hours.

[0092] (Example 15) Sample for Example 15 was obtained in the same manner as in Example 9, except that the firing was performed under the conditions of heating time of 1.5 hours, holding temperature of 600°C, holding time of 2 hours, and cooling time of 1.75 hours.

[0093] (Example 16) Sample for Example 16 was obtained in the same manner as in Example 9, except that the firing was performed under the conditions of heating time of 1.75 hours, holding temperature of 700°C, holding time of 2 hours, and cooling time of 1.95 hours.

[0094] (Example 17) Sample for Example 17 was obtained in the same manner as in Example 9, except that the firing was performed under the conditions of heating time of 2 hours, holding temperature of 800°C, holding time of 6 hours, and cooling time of 2.08 hours.

[0095] (Example 18) Sample for Example 18 was obtained in the same manner as in Example 9, except that the firing was performed under the conditions of heating time of 2 hours, holding temperature of 800°C, holding time of 0 hours, and cooling time of 2.08 hours.

[0096] (Example 19) Sample for Example 19 was obtained in the same manner as in Example 9, except that the firing was performed under the conditions of heating time of 2 hours, holding temperature of 800°C, holding time of 2 hours, and cooling time of 2.08 hours.

[0097] (Example 20) Sample for Example 20 was obtained in the same manner as in Example 9, except that the firing conditions were 2.13 hours of heating, 850°C, 2 hours of holding time, and 2.13 hours of cooling time.

[0098] (Comparative Example 3) A sample for Comparative Example 3 was obtained in the same manner as in Example 9, except that the firing was performed under the conditions of a heating time of 50 minutes, a holding temperature of 350°C, a holding time of 2 hours, and a cooling time of 0.75 hours.

[0099] (Comparative Example 4) A sample for Comparative Example 4 was obtained in the same manner as in Example 9, except that the firing was performed under the conditions of heating time of 2.25 hours, holding temperature of 900°C, holding time of 2 hours, and cooling time of 2.2 hours.

[0100] The chemical formulas of the samples obtained in Examples 9-20 and Comparative Examples 3 and 4 as described above were all Mg6Al2O9.

[0101] For each sample in Examples 9-20 and Comparative Examples 3 and 4, the powder properties (molar ratio and BET specific surface area) and the adsorption rates of various anions (blank concentrations F: 10 ppm, B: 10 ppm, Cr: 80 ppm, P: 30 ppm) were measured. These results are shown in Table 2 below.

[0102] [Table 2]

[0103] (Example 21) In a 1 L reaction vessel containing a small amount of water, 252 mL of 1.5 mol / L magnesium chloride aqueous solution, 94 mL of 1.0 mol / L aluminum chloride aqueous solution, and a mixed solution of 278 mL of 3.4 mol / L sodium hydroxide aqueous solution and 76 mL of 0.75 mol / L sodium carbonate aqueous solution were simultaneously added dropwise while stirring to obtain the reaction product. The pH during the reaction was 11.0. After washing the obtained reaction product with water, it was dried overnight at 105°C and then pulverized. The resulting powder was calcined under the conditions of heating time 1 hour, holding temperature 400°C, holding time 12 hours, and cooling time 1 hour to obtain the sample for Example 21.

[0104] (Example 22) Sample for Example 22 was obtained in the same manner as in Example 21, except that the firing conditions were: heating time of 1.25 hours, holding temperature of 500°C, holding time of 2 hours, and cooling time of 1.25 hours.

[0105] (Example 23) Sample for Example 23 was obtained in the same manner as in Example 21, except that the firing conditions were: heating time of 1.5 hours, holding temperature of 600°C, holding time of 2 hours, and cooling time of 1.75 hours.

[0106] (Example 24) Sample for Example 24 was obtained in the same manner as in Example 21, except that the firing conditions were: heating time of 1.75 hours, holding temperature of 700°C, holding time of 2 hours, and cooling time of 1.95 hours.

[0107] (Comparative Example 5) A sample for Comparative Example 5 was obtained in the same manner as in Example 21, except that the firing was performed under the conditions of heating time of 50 minutes, holding temperature of 350°C, holding time of 2 hours, and cooling time of 0.75 hours.

[0108] (Comparative Example 6) A sample for Comparative Example 6 was obtained in the same manner as in Example 21, except that the firing was performed under the conditions of heating time of 1 hour, holding temperature of 400°C, holding time of 2 hours, and cooling time of 4 hours.

[0109] (Comparative Example 7) A sample for Comparative Example 7 was obtained in the same manner as in Example 21, except that the firing was performed under the conditions of heating time of 1 hour, holding temperature of 400°C, holding time of 2 hours, and cooling time of 1 hour.

[0110] (Comparative Example 8) A sample for Comparative Example 8 was obtained in the same manner as in Example 21, except that the firing was performed under the conditions of heating time of 2 hours, holding temperature of 800°C, holding time of 6 hours, and cooling time of 2.08 hours.

[0111] (Comparative Example 9) A sample for Comparative Example 9 was obtained in the same manner as in Example 21, except that the firing was performed under the conditions of heating time of 2.13 hours, holding temperature of 850°C, holding time of 2 hours, and cooling time of 2.13 hours.

[0112] (Comparative Example 10) A sample for Comparative Example 10 was obtained in the same manner as in Example 21, except that the firing was performed under the conditions of heating time of 2.25 hours, holding temperature of 900°C, holding time of 2 hours, and cooling time of 2.2 hours.

[0113] The chemical formulas of the samples obtained in Examples 21-24 and Comparative Examples 5-10 as described above are all Mg8Al2O. 11 That was the case.

[0114] For each sample in Examples 21-24 and Comparative Examples 5-10, the powder properties (molar ratio and BET specific surface area) and the adsorption rates of various anions (blank concentrations F: 10 ppm, B: 10 ppm, Cr: 80 ppm, P: 30 ppm) were measured. These results are shown in Table 3 below.

[0115] [Table 3]

[0116] Furthermore, the adsorption rates of various anions with different blank concentrations (blank concentrations F: 10 ppm, B: 10 ppm, Cr: 80 ppm, P: 30 ppm) were additionally measured for each sample in Examples 3, 4, 7, 15, 16, 23, and 24, and Comparative Examples 2, 4, and 10. These results are shown in Table 4 below.

[0117] [Table 4]

[0118] Regarding the adsorption rates of various anions, a good adsorption rate is indicated by an adsorption rate of 80% or higher for F: 50 ppm, 80% or higher for Cr: 100 ppm, 90% or higher for P: 20 ppm, and 80% or higher for P: 40 ppm.

[0119] As shown in Tables 1 to 4, each sample from Examples 1 to 24 of the present invention was found to be able to remove four types of anions with high adsorption rates. Furthermore, it was found that these samples could efficiently adsorb and remove not only monatomic anions, but also polyatomic oxoanions and transition metal oxoanions. [Industrial applicability]

[0120] The composite metal oxide of the present invention can be suitably used in a wide range of products, including adsorbents for liquids such as water or gases, as well as liquid purification materials, filtration devices (e.g., packed columns), composite fibers, and resin stabilizers.

Claims

1. A composite metal oxide represented by the following formula (1), A composite metal oxide characterized by having a solid base content of 3.74 mmol / g or more. (Mg １－ｘ Al ｘ )O １＋ｘ／２ ・・・(1) In equation (1), x is a number that satisfies 0.18 ≤ x ≤ 0.

45.

2. BET specific surface area is 150 m² ２ / g to 350m ２ The composite metal oxide according to claim 1, wherein the range is within / g.

3. A mixture comprising the composite metal oxide and layered double hydroxide described in claim 1.

4. The mixture according to claim 3, wherein the layered double hydroxide is represented by the following formula (2). [Mg １－ｘ Al ｘ (OH) ２ ] ｘ＋ [(A ｎ－ ) ｘ／ｎ ・mH ２ O]・・・(2) In equation (2), A ｎ－ CO ３ ２－ and OH － This represents an anion selected from the group consisting of the following, where n is 1 or 2, x is a number satisfying 0.18 ≤ x ≤ 0.45, and m is a number satisfying 0 ≤ m < 1.

5. The mixture according to claim 3, wherein the mixing ratio of the composite metal oxide and the layered double hydroxide is in the range of 99.99:0.01 to 50:50 by mass ratio.

6. An adsorbent comprising the composite metal oxide described in claim 1.

7. A method for treating a liquid, comprising contacting the liquid with the composite metal oxide described in claim 1.

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