Composite metal oxide

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

complex metal oxides

[0001] The present invention relates to a composite metal oxide used for water treatment and the like.

[0002] Water treatment technologies have been developed mainly for the purposes of water supply treatment, sewage treatment, and wastewater treatment, and are mainly divided into biological treatment and physicochemical treatment. Biological treatment is a method of decomposing pollutants through the action of microorganisms, while physicochemical treatment methods vary depending on the state of the pollutants contained in the water.

[0003] For example, when the pollutants are suspended or colloidal substances, they are usually separated and removed by precipitation and filtration. However, when the pollutants are fine suspended or colloidal substances that cannot be separated and removed, they are insolubilized with a flocculant and then separated and removed.

[0004] Furthermore, when the pollutants are dissolved substances contained in drinking water, industrial wastewater, etc., they are removed by means of electrodialysis, reverse osmosis, evaporation, ion exchange, adsorption, or the like. However, electrodialysis, reverse osmosis, and evaporation require large equipment costs and are limited in terms of the locations where they can be performed. Although ion exchange methods using ion exchange resins can be performed with relatively inexpensive equipment, they require a highly concentrated alkaline aqueous solution for regeneration, which increases the regeneration cost. For these reasons, adsorption methods, which can remove pollutants contained in water with relatively inexpensive equipment and treatment costs, have attracted attention.

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

[0006] Furthermore, Non-Patent Document 1 discloses a water purification method in which various anions such as phosphate ions and chloride ions are removed from water using hydrotalcite (HT) or magnesium-aluminum oxide (Mg—Al oxide).

[0007] Japanese Patent Application Laid-Open No. 2002-136965

[0008] 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 195), pp. 10-16

[0009] Drinking water, industrial wastewater, and other water may contain multiple types of anions. However, it is practically difficult to simultaneously remove multiple types of anions at high removal rates using conventional composite metal oxides, so in some cases, the water must be treated multiple times.

[0010] Therefore, an object of the present invention is to provide a composite metal oxide having excellent anion adsorption properties, which can remove a plurality of types of anions at high adsorption rates.

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

[0012] (First Disclosure) 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) [In formula (1), x is a number that satisfies 0.18≦x≦0.45.]

[0013] (Second Disclosure) The second disclosure is the first disclosure, wherein the BET specific surface area is 150 m ２ / g~350m 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) In the fourth disclosure, in the third disclosure, the layered double hydroxide is a layered double hydroxide represented by the following formula (2): [Mg １－ｘ Al ｘ (OH) ２ ] ｘ＋ [(A ｎ－ ) ｘ／ｎ ・mH ２ O] (2) [In formula (2), A ｎ－ is CO ３ ２－ and OH － wherein n is 1 or 2, x is a number satisfying 0.18≦x≦0.45, and m is a number satisfying 0≦m<1.

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

[0017] (Sixth Disclosure) The sixth disclosure is an adsorbent comprising the composite metal oxide according to the first disclosure or the second disclosure.

[0018] (Seventh Disclosure) The seventh disclosure is a method for treating a liquid, comprising contacting the liquid with the composite metal oxide according to the first disclosure or the second disclosure.

[0019] (Eighth Disclosure) The eighth disclosure is an adsorbent comprising a mixture of any one of the third to fifth disclosures.

[0020] (Ninth Disclosure) A ninth disclosure is a method for treating a liquid, comprising contacting the liquid with any of the mixtures according to the third to fifth disclosures.

[0021] (Tenth Disclosure) A tenth disclosure is a method for treating a liquid, comprising contacting the liquid with the adsorbent according to the sixth disclosure.

[0022] The mixed metal oxide of the present invention can remove at least four types of anions at high adsorption rates, and can efficiently adsorb and remove not only monoatomic anions but also polyatomic oxoanions and transition metal oxoanions.

[0023] Hereinafter, preferred embodiments of the mixed metal oxide of the present invention will be described in detail. In this specification, various numerical ranges mean ranges including the upper and lower limit values ​​unless otherwise specified.

[0024] [Composite Metal Oxide] In one embodiment of the present invention, the composite metal oxide 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) [In formula (1), x is a number that satisfies 0.18≦x≦0.45.]

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

[0026] The hydrotalcite-based compound used as the raw material for the composite metal oxide can be synthesized, for example, as follows. First, a mixed aqueous solution of a magnesium salt and an aluminum salt is reacted with an alkaline substance to obtain a slurry. The obtained slurry may be subjected to a hydrothermal treatment to induce crystal growth. The slurry is then subjected to solid-liquid separation, followed by washing, drying, and pulverization to obtain a powder of the hydrotalcite-based compound.

[0027] The magnesium salt used in the synthesis of the hydrotalcite-based compound is not particularly limited, but examples thereof include magnesium chloride, magnesium nitrate, magnesium sulfate, magnesium hydroxide, etc. Among these, it is preferable to use at least one of magnesium sulfate and magnesium chloride as the magnesium salt. These magnesium salts have the advantages of being able to reduce material costs and being easily available.

[0028] The aluminum salt used in the synthesis of the hydrotalcite-based compound is not particularly limited, but examples thereof include aluminum chloride, aluminum nitrate, aluminum sulfate, and sodium aluminate. ２ The molar ratio of is preferably in the range of 2 to 10, more preferably in the range of 4 to 8.

[0029] The alkaline substance used in the synthesis of the hydrotalcite-based compound is not particularly limited, but examples thereof include aqueous solutions of caustic soda, ammonia, potassium hydroxide, sodium carbonate, and the like.

[0030] The composite metal oxides obtained from such hydrotalcite-type compounds can easily reconstruct a hydrotalcite-like structure by absorbing ions and moisture from the atmosphere. Furthermore, because these composite metal oxides are positively charged, they easily adsorb anions such as fluoride ions and chloride ions. When the composite metal oxide absorbs moisture from the atmosphere and transforms into a hydroxide, it can incorporate anions between its layers (i.e., intercalate).

[0031] The composite metal oxide of this embodiment has a solid base amount of 3.70 mmol / g or more. The composite metal oxide of this embodiment is represented by formula (1) above and has the specific solid base amount, thereby enabling it to remove at least four types of anions at high adsorption rates. Specifically, the composite metal oxide of this embodiment can remove anions containing fluorine, boron, chromium, and phosphorus at high adsorption rates. Furthermore, this composite metal oxide can efficiently adsorb and remove not only monoatomic anions, but also polyatomic oxoanions and transition metal oxoanions. As a result, the composite metal oxide of this embodiment can significantly contribute to water purification, thereby advantageously contributing to the achievement of the Sustainable Development Goals (SDGs) adopted at the United Nations Summit.

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

[0033] The solid base content of the composite metal oxide can be controlled by appropriately adjusting the thermal history during the production of the composite metal oxide. Specific examples of the thermal history include calcination conditions such as the temperature rise time, holding temperature, holding time, and temperature fall time when calcining a hydrotalcite-based compound. Calcination of a hydrotalcite-based compound generally involves a series of steps, including raising the temperature from room temperature, holding at the holding temperature for a certain period of time, lowering the temperature, and then returning to room temperature.

[0034] Here, in this specification, the meanings of the various terms related to the calcination of hydrotalcite-based compounds (samples) are as follows: Heat-up time: When calcining a sample in an electric furnace, this refers to the time it takes to heat from room temperature to reach the desired maximum temperature. Holding temperature: When calcining a sample in an electric furnace, this refers to the desired maximum temperature. Also referred to as the calcination temperature. Holding time: When calcining a sample in an electric furnace, this refers to the time it takes to maintain the holding temperature. Temperature-down time: When calcining a sample in an electric furnace, this refers to the time it takes to cool from the holding temperature after the holding time has elapsed to reach room temperature. Note that cooling includes active cooling using a cooling means as well as gradual cooling such as by leaving it to cool.

[0035] The calcination conditions for producing a composite metal oxide from a hydrotalcite-based compound are not particularly limited as long as they result in a solid base amount within the above-mentioned specific range. Examples of such calcination conditions include a temperature-raising time of preferably 0.5 to 8 hours, more preferably 0.5 to 6 hours. Similarly, a holding temperature of preferably 350 to 900°C, more preferably 400 to 850°C. Furthermore, a holding time of preferably 0 to 18 hours, more preferably 0 to 15 hours. Furthermore, a temperature-lowering time of preferably 0.5 to 4 hours, more preferably 0.8 to 3 hours.

[0036] The composite metal oxide of the present invention has a BET specific surface area of ​​150 m ２ / g~350m ２ When the BET specific surface area is within this range, high adsorption ability for a plurality of types of anions can be more reliably exhibited.

[0037] In this specification, the BET specific surface area refers to the specific surface area of ​​a particulate composite metal oxide measured by the BET method. A specific method for measuring the BET specific surface area will be described later.

[0038] The BET specific surface area of ​​the composite metal oxide is 150 m ２ / g to 300m ２ / g, and more preferably in the range of 155m ２ / g~260m ２ / g is 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 may contain 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 the 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. Because layered double hydroxides have low bulk, a mixture containing the composite metal oxide and a layered double hydroxide will be less bulky than an adsorbent composed only of the composite metal oxide. Therefore, such a mixture will be easier to handle when actually used as an adsorbent.

[0040] The layered double hydroxide in the mixture is not particularly limited, but examples thereof include double hydroxides represented by the following formula (2): [Mg １－ｘ Al ｘ (OH) ２ ] ｘ＋ [(A ｎ－ ) ｘ／ｎ ・mH ２ O] (2) [In formula (2), A ｎ－ is CO ３ ２－ and OH － wherein 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 the above formula (2) is not particularly limited, but examples thereof include hydrotalcite compounds that serve as raw materials for composite metal oxides, hygroscopic composite metal oxides, etc. These layered double hydroxides have the advantage of being able to reduce material costs and being easily available.

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

[0043] [Treatment Method] The mixed metal oxide of the present invention can also be used as an adsorbent for removing multiple types of anions contained in liquids other than water, gases, etc. However, from the viewpoint of removing multiple types of anions at high adsorption rates, the mixed metal oxide of the present invention is preferably used as an adsorbent for water or a liquid containing a liquid other than water.

[0044] Therefore, one aspect of the present invention is a method for treating a liquid, which comprises contacting a liquid containing water or a liquid other than water with the mixed metal oxide of the present invention. By using this method for treating a liquid, it is possible to remove multiple types of anions from the liquid at high adsorption rates.

[0045] The mixed metal oxide of the present invention may be used as an adsorbent for a liquid containing water or a liquid other than water in the form of a mixture with the layered double hydroxide. Therefore, another aspect of the present invention is a method for treating a liquid, which comprises contacting a mixture of the mixed metal oxide of the present invention and the layered double hydroxide with a liquid containing water or a liquid other than water.

[0046] The composite metal oxide of the present invention can be molded according to the intended use. 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 the powdered composite metal oxide into a shape suitable for the adsorption treatment. Examples of the shape of the molded body include spherical, approximately spherical, cylindrical, granular, pellet, and tablet shapes.

[0047] The granulation method or molding method used to produce the compact is not particularly limited, and known methods such as dry granulation or wet granulation can be used. Examples of dry granulation methods include a dry roller compactor method and a roll granulator method. Examples of wet granulation methods include a spray drying method, a fluidized bed granulation method, a tumbling granulation method, an agitation granulation method, and an extrusion granulation method. The compact containing the composite metal oxide of the present invention can control the permeability and adsorption effect of a liquid or gas containing the adsorbent during an adsorption operation.

[0048] Furthermore, the composite metal oxide of the present invention can be blended with various known additives and then granulated or molded. In other words, one aspect of the present invention is an additive-containing compact. Examples of additives include fibers, resins, and clay minerals. Examples of fibers include chemical fibers, recycled fibers, and natural fibers. Furthermore, examples of natural fibers include cellulose. Examples of clay minerals include bentonite, sepiolite, and kaolin. The additive-containing compact containing the composite metal oxide of the present invention allows for control of the strength and porosity of the compact, and therefore, the adsorption performance.

[0049] The mixed metal oxide of the present invention can be used in a variety of applications such as the following.

[0050] One aspect of the present invention is a liquid purification material. Specific examples of liquid purification materials include a liquid purification material comprising the composite metal oxide of the present invention and a bag containing the composite metal oxide, the bag having pores of a size that prevents the composite metal oxide from passing through. The bag may be made of a material such as a nonwoven fabric. A liquid purification material containing the composite metal oxide of the present invention allows for easy separation of the liquid from the liquid purification material after contacting the liquid with the liquid purification material.

[0051] One aspect of the present invention is a filtration device. Specific examples of the filtration device 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 in 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 fibers. Examples of fibers include at least one type of fiber selected from chemical fibers, regenerated fibers, and natural fibers. Furthermore, examples of natural fibers include cellulose. The means for supporting the composite metal oxide on fibers is not particularly limited, and the composite metal oxide may be kneaded into the interior of the fibers during fiber production, or the composite metal oxide may be attached to the fiber surface using a treatment agent or the like.

[0053] 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. The composite metal oxide of the present invention is produced by calcining a hydrotalcite-type compound to remove interlayer water, so that even when blended into a resin and heated, little moisture is generated. As a result, a resin composition containing the composite metal oxide of the present invention can suppress foaming during heat processing compared to a resin composition blended with a hydrotalcite-type compound.

[0054] The present invention is not limited to the above-described embodiments or the examples to be described later, and appropriate combinations, substitutions, modifications, etc. are possible within the scope that does not deviate from the object and intent of the present invention.

[0055] EXAMPLES The present invention will be explained in more detail below by way of examples and comparative examples, but the present invention is not limited to these examples.

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

[0057] <Mole ratio (MgO / Al ２ O ３ The molar ratio was measured by the acid dissolution method described below. However, for samples that were not dissolved by the acid dissolution method, the molar ratio was measured by the alkali fusion method described below.

[0058] (Acid dissolution method) 0.5 g of sample was placed in a 100 mL beaker, and 10 mL of dilute hydrochloric acid and 5 mL of perchloric acid were added. The mixture was heated on a hot plate to dissolve the sample. The sample solution in the beaker was transferred to a 250 mL measuring flask and diluted to 250 mL. The MgO content and Al content were measured using this diluted sample solution as follows: ２ O ３ The contents were quantified. (1) Quantification of MgO 10 mL of the above sample solution was placed in a 200 mL beaker using a volumetric pipette and diluted to 100 mL with ion-exchanged water. 5 mL of aqueous triethanolamine solution was added to this diluted sample solution, and ammonium chloride ammonia buffer solution was added dropwise to adjust the pH to 10 using a pH meter. 15 drops of Universal BT test solution were added as an indicator, and the solution was titrated with 0.01 mol / L-EDTA standard solution. (2) Al ２ O ３ Quantification of MgO and Al: 10 mL of the above sample solution was placed in a 200 mL beaker using a whole pipette, and 30 mL of 0.01 mol / L-CyDTA standard solution was added using a whole pipette. Hexamethylenetetramine was added so that the pH was adjusted to 5-5.5 using a pH meter. Three drops of XO test solution were added as an indicator, and the solution was titrated with 0.01 mol / L zinc acetate standard solution. The MgO content and Al content determined in this way were ２ O ３ Using the content, the molar ratio (MgO / Al ２ O ３ ) was calculated.

[0059] (Alkali fusion method) 0.5 g of sample was placed in a platinum crucible, 3 g of boric acid and 5 g of sodium carbonate were added, and the mixture was melted in an electric furnace at 950°C for 2 hours. The melt was transferred to a 200 mL beaker, and 100 mL of dilute hydrochloric acid was added to dissolve the sample. The solution was then transferred to a 250 mL measuring flask and diluted to 250 mL. The MgO content was quantified and the Al content was measured. ２ O ３ The content was determined in the same manner as in the acid dissolution method, and the molar ratio was calculated.

[0060] <BET Specific Surface Area> Measurement was carried out using a high-precision specific surface area and pore distribution measuring device "BELSORP-max" manufactured by Microtrac-Bell Corporation.

[0061] <Solid Base Amount> 0.2 g of sample was placed in a stoppered Erlenmeyer flask, and 5 mL of benzene (Wako Reagent Special Grade) was added. 1 mL of a 0.1 wt % phenolphthalein benzene solution was added as an indicator with a pKa of 9.3, causing the sample solution to turn pink. The sample solution was titrated with a 0.1 mol / L benzoic acid-benzene solution until it turned white, and the amount of benzoic acid-benzene solution required for the titration was designated A (mL). The Erlenmeyer flask was stoppered and left to stand for 24 hours, at which point the sample solution returned to pink. The sample solution was then titrated again with a 0.1 mol / L benzoic acid-benzene solution until it turned white, and the amount of benzoic acid-benzene solution required for the titration was designated B (mL). This procedure was repeated once more, and the amount of benzoic acid-benzene solution required for the titration was designated C (mL). The amount of solid base was calculated from the total amount of the three titrations based on the following formula: Amount of solid base (mmol / g) = 0.1 (A + B + C) / 0.2 g

[0062] <Adsorption Rate of Various Anions> The adsorption rates of a plurality of types of anions contained in water were measured for each type and concentration of anion as follows.

[0063] (Fluorine (F) Adsorption Rate When Blank Concentration is 10 ppm) 0.03 g of sample was placed in a 50 mL centrifuge tube, and 30 mL of a sodium fluoride aqueous solution with a fluorine concentration of 10 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. 10 mL of the obtained filtrate was placed in a 20 mL volumetric flask, and 2 mL of Alfusson test solution (2.5 g of Alfusson reagent dissolved in 50 mL of ion-exchanged water) and 4 mL of acetone were added, followed by dilution to 20 mL with ion-exchanged water. The diluted filtrate was allowed to stand in a dark place for 1 hour, and then the fluorine concentration D (ppm) was measured at 620 nm using a spectrophotometer "U-4100" manufactured by Hitachi High-Tech Science Corporation, and the adsorption rate was calculated according to the following formula: Adsorption rate (%) = (10 - D) / 10 × 100

[0064] (Fluorine (F) Adsorption Rate When Blank Concentration is 50 ppm) 0.03 g of sample was placed in a 50 mL centrifuge tube, and 30 mL of a sodium fluoride aqueous solution with a fluorine concentration of 50 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. 10 mL of the obtained filtrate was placed in a 20 mL volumetric flask, and 2 mL of Alfusson test solution (2.5 g of Alfusson reagent dissolved in 50 mL of ion-exchanged water) and 4 mL of acetone were added, followed by dilution to 20 mL with ion-exchanged water. The diluted filtrate was allowed to stand in a dark place for 1 hour, and then the fluorine concentration E (ppm) was measured at 620 nm using a spectrophotometer "U-4100" manufactured by Hitachi High-Tech Science Corporation, and the adsorption rate was calculated according to the following formula: Adsorption rate (%) = (50 - E) / 50 × 100

[0065] (Boron (B) adsorption rate when blank concentration is 10 ppm) 0.03 g of sample was placed in a 50 mL centrifuge tube, and 30 mL of an aqueous sodium tetraborate solution with a boron concentration of 10 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 boron concentration F (ppm) of the obtained filtrate was measured using an ICP atomic 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 x 100

[0066] (Chromium (Cr) Adsorption Rate when Blank Concentration is 80 ppm) 0.03 g of sample was placed in a 50 mL centrifuge tube, and 30 mL of a 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 atomic 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 x 100

[0067] (Chromium (Cr) Adsorption Rate when Blank Concentration is 100 ppm) 0.03 g of sample was placed in a 50 mL centrifuge tube, and 30 mL of a 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 atomic 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 x 100

[0068] (Phosphorus (P) adsorption rate when blank concentration is 20 ppm) 0.03 g of sample was placed in a 50 mL centrifuge tube, and 30 mL of an aqueous solution of sodium dihydrogen phosphate with a phosphorus concentration of 20 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 phosphorus concentration I (ppm) of the obtained filtrate was measured using an ICP atomic 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 blank concentration is 30 ppm) 0.03 g of sample was placed in a 50 mL centrifuge tube, and 30 mL of an aqueous sodium dihydrogen phosphate solution with a phosphorus concentration of 30 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 phosphorus concentration J (ppm) of the obtained filtrate was measured using an ICP atomic 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 blank concentration is 40 ppm) 0.03 g of sample was placed in a 50 mL centrifuge tube, and 30 mL of an aqueous sodium dihydrogen phosphate solution with a phosphorus concentration of 40 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 phosphorus concentration K (ppm) of the obtained filtrate was measured using an ICP atomic 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 of the present invention and comparative examples will be described.

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

[0073] Example 2 A sample of Example 2 was obtained in the same manner as in Example 1, except that firing was performed under conditions of a temperature rise time of 1.25 hours, a holding temperature of 500° C., a holding time of 2 hours, and a temperature fall time of 1.25 hours.

[0074] Example 3 A sample of Example 3 was obtained in the same manner as in Example 1, except that firing was performed under conditions of a temperature rise time of 1.5 hours, a holding temperature of 600° C., a holding time of 2 hours, and a temperature fall time of 1.75 hours.

[0075] Example 4 A sample of Example 4 was obtained in the same manner as in Example 1, except that firing was performed under conditions of a temperature rise time of 1.75 hours, a holding temperature of 700° C., a holding time of 2 hours, and a temperature fall time of 1.95 hours.

[0076] Example 5 A sample of Example 5 was obtained in the same manner as in Example 1, except that firing was performed under conditions of a temperature rise time of 2 hours, a holding temperature of 800° C., a holding time of 6 hours, and a temperature fall time of 2.08 hours.

[0077] Example 6 A sample of Example 6 was obtained in the same manner as in Example 1, except that firing was performed under conditions of a temperature rise time of 2 hours, a holding temperature of 800° C., a holding time of 0 hour, and a temperature fall time of 2.08 hours.

[0078] Example 7 A sample of Example 7 was obtained in the same manner as in Example 1, except that firing was performed under conditions of a temperature rise time of 2 hours, a holding temperature of 800° C., a holding time of 2 hours, and a temperature fall time of 2.08 hours.

[0079] Example 8 A sample of Example 8 was obtained in the same manner as in Example 1, except that firing was performed under conditions of a temperature rise time of 2.13 hours, a holding temperature of 850° C., a holding time of 2 hours, and a temperature fall time of 2.13 hours.

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

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

[0082] The chemical formula of each of the samples obtained in the above-described manner in Examples 1 to 8 and Comparative Examples 1 and 2 was Mg ４．５ Al ２ O ７．５ It was.

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

[0084]

[0085] Regarding the adsorption rates of various anions, an index of a good adsorption rate is 90% or more for F: 10 ppm, 90% or more for B: 10 ppm, 90% or more for Cr: 80 ppm, or 90% or more for P: 30 ppm.

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

[0087] Example 10 A sample of Example 10 was obtained in the same manner as in Example 9, except that firing was performed under conditions of a temperature rise time of 4 hours, a holding temperature of 400° C., a holding time of 2 hours, and a temperature fall time of 1 hour.

[0088] Example 11 A sample of Example 11 was obtained in the same manner as in Example 9, except that firing was performed under conditions of a temperature rise time of 1 hour, a holding temperature of 400° C., a holding time of 2 hours, and a temperature fall time of 1 hour.

[0089] Example 12 A sample of Example 12 was obtained in the same manner as in Example 9, except that firing was performed under conditions of a temperature rise time of 4 hours, a holding temperature of 400° C., a holding time of 2 hours, and a temperature fall time of 4 hours.

[0090] Example 13 A sample of Example 13 was obtained in the same manner as in Example 9, except that firing was performed under conditions of a temperature rise time of 1 hour, a holding temperature of 400° C., a holding time of 12 hours, and a temperature fall time of 1 hour.

[0091] Example 14 A sample of Example 14 was obtained in the same manner as in Example 9, except that firing was performed under conditions of a temperature rise time of 1.25 hours, a holding temperature of 500°C, a holding time of 2 hours, and a temperature fall time of 1.25 hours.

[0092] Example 15 A sample of Example 15 was obtained in the same manner as in Example 9, except that firing was performed under conditions of a temperature rise time of 1.5 hours, a holding temperature of 600°C, a holding time of 2 hours, and a temperature fall time of 1.75 hours.

[0093] Example 16 A sample of Example 16 was obtained in the same manner as in Example 9, except that firing was performed under conditions of a temperature rise time of 1.75 hours, a holding temperature of 700°C, a holding time of 2 hours, and a temperature fall time of 1.95 hours.

[0094] Example 17 A sample of Example 17 was obtained in the same manner as in Example 9, except that firing was performed under conditions of a temperature rise time of 2 hours, a holding temperature of 800° C., a holding time of 6 hours, and a temperature fall time of 2.08 hours.

[0095] Example 18 A sample of Example 18 was obtained in the same manner as in Example 9, except that firing was performed under conditions of a temperature rise time of 2 hours, a holding temperature of 800° C., a holding time of 0 hour, and a temperature fall time of 2.08 hours.

[0096] Example 19 A sample of Example 19 was obtained in the same manner as in Example 9, except that firing was performed under conditions of a temperature rise time of 2 hours, a holding temperature of 800° C., a holding time of 2 hours, and a temperature fall time of 2.08 hours.

[0097] Example 20 A sample of Example 20 was obtained in the same manner as in Example 9, except that firing was performed under conditions of a temperature rise time of 2.13 hours, a holding temperature of 850°C, a holding time of 2 hours, and a temperature fall time of 2.13 hours.

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

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

[0100] The chemical formula of each of the samples obtained in Examples 9 to 20 and Comparative Examples 3 and 4 was Mg ６ Al ２ O ９ It was.

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

[0102]

[0103] Example 21: A 1 L reaction vessel containing a small amount of water was simultaneously dripped with 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 while stirring to obtain a reaction product. The pH during the reaction was 11.0. The resulting reaction product was washed with water, dried overnight at 105°C, and pulverized. The resulting powder was calcined under the following conditions: a heating time of 1 hour, a holding temperature of 400°C, a holding time of 12 hours, and a cooling time of 1 hour, to obtain a sample of Example 21.

[0104] Example 22 A sample of Example 22 was obtained in the same manner as in Example 21, except that firing was performed under conditions of a temperature rise time of 1.25 hours, a holding temperature of 500°C, a holding time of 2 hours, and a temperature fall time of 1.25 hours.

[0105] Example 23 A sample of Example 23 was obtained in the same manner as in Example 21, except that firing was performed under conditions of a temperature rise time of 1.5 hours, a holding temperature of 600°C, a holding time of 2 hours, and a temperature fall time of 1.75 hours.

[0106] Example 24 A sample of Example 24 was obtained in the same manner as in Example 21, except that firing was performed under conditions of a temperature rise time of 1.75 hours, a holding temperature of 700°C, a holding time of 2 hours, and a temperature fall time of 1.95 hours.

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

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

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

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

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

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

[0113] The chemical formula of each of the samples obtained in the above-described manner in Examples 21 to 24 and Comparative Examples 5 to 10 was Mg ８ Al ２ O １１ It was.

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

[0115]

[0116] Furthermore, the adsorption rates of various anions at different blank concentrations (blank concentrations: F: 10 ppm, B: 10 ppm, Cr: 80 ppm, P: 30 ppm) were additionally measured for each sample of 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]

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

[0119] As shown in Tables 1 to 4, it was found that each of the samples of Examples 1 to 24 of the present invention was able to remove each of the four types of anions at a high adsorption rate. Furthermore, it was found that each of these samples was able to efficiently adsorb and remove not only monoatomic anions but also polyatomic oxoanions and transition metal oxoanions.

[0120] The composite metal oxide of the present invention can be suitably used in a wide range of products, such as 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 having a solid base amount of 3.70 mmol / g or more. (Mg １－ｘ Al ｘ )O １＋ｘ／２ ・・・(1) In formula (1), x is a number that satisfies 0.18≦x≦0.

45.

2. BET specific surface area is 150m ２ / g~350m ２ The mixed metal oxide according to claim 1, wherein the metal oxide content is in the range of 1 / g.

3. A mixture comprising the complex metal oxide of claim 1 and a layered double hydroxide.

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 formula (2), A ｎ－ CO ３ ２－ and OH － wherein 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. 4. The mixture according to claim 3, wherein a mixing ratio of the composite metal oxide to the layered double hydroxide is within a range of 99.99:0.01 to 50:50 in terms of mass ratio.

6. An adsorbent comprising the complex metal oxide of claim 1.

7. A method for treating a liquid, comprising contacting the liquid with the mixed metal oxide of claim 1.