Adsorption method and mesoporous alumina used in the method

Abstract

A method for adsorbing elements belonging to periods 4 to 6 and groups 3 to 15 of the periodic table is provided. The method includes: preparing mesoporous alumina that satisfies at least one of the following: (1) a surface hydroxyl content of 3.5 mmol / g or more; (2) a low-temperature CO2 desorption amount in a CO2 temperature desorption analysis of 5 μmol / g or more; and (3) a low-temperature NH3 desorption amount in an NH3 temperature desorption analysis of 25 μmol / g or more; and contacting a liquid containing the target element with the mesoporous alumina to adsorb the target element onto the mesoporous alumina. The target element is at least one selected from the group consisting of elements belonging to periods 4 to 6 and groups 3 to 15 of the periodic table.

Description

Technical Field

[0001] This invention relates to an adsorption method and mesoporous alumina used in the method.

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 061,56, filed August 6, 2020, the entire contents of which are incorporated herein by reference. Background Technology

[0003] Porous metal oxides are known to be used as adsorbent materials and catalyst supports. For example, Patent Document 1 relates to a technology for adsorbing and removing radioactive cesium and strontium from natural water and polluted water, proposing a cesium-strontium adsorbent material formed from a phase-separation porous glass and a system that forms a stable glass solidified body after adsorption. Additionally, Patent Document 2 describes... 99m Useful porous metal oxides such as molybdenum (Mo) adsorbent materials for Tc generators and their manufacturing methods.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-000764

[0007] Patent Document 2: International Publication No. 2017 / 126602 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] The technology described in Patent Document 1 is based on the use of a phase-separated porous glass, which is mostly composed of SiO2 (claim 1, paragraph

[0051] , etc.), without using an adsorbent material with alumina as the main component. Furthermore, in Patent Document 1, the elements adsorbed on the adsorbent material (the target adsorbent elements) are limited to cesium and strontium, and other elements are not intended for adsorption. Patent Document 2 relates to the Mo retention of other metal oxides such as porous alumina, focusing on the manufacturing method and structural characteristics (specific surface area, pore volume, average pore size, etc.) of the porous metal oxide, but does not specifically study the retention of elements other than Mo. It would be beneficial to provide an adsorption method that uses an adsorbent material and is also applicable to the adsorption of elements from Groups 3 to 15 of the periodic table other than Mo.

[0010] The object of the present invention is to provide an adsorption method that solves the above-mentioned problems. Another related object is to provide an adsorbent material suitable for carrying out the above-mentioned adsorption method.

[0011] Solution for solving the problem

[0012] According to this specification, an adsorption method is provided for elements belonging to periods 4 to 6 and groups 3 to 15 of the periodic table. The adsorption method includes the following steps: preparing mesoporous alumina; and contacting the mesoporous alumina with a liquid containing the target element, thereby adsorbing the target element onto the mesoporous alumina. The target element is at least one selected from the group consisting of elements belonging to periods 4 to 6 and groups 3 to 15 of the periodic table. The mesoporous alumina used satisfies at least one of the following conditions (1) to (3).

[0013] (1) The amount of surface hydroxyl groups is above 3.5 mmol / g.

[0014] (2) In the temperature-induced desorption analysis of probe molecules using CO2, the amount of CO2 desorbed from peaks with peak temperatures below 200℃ (hereinafter also referred to as "low-temperature CO2 desorption amount") is above 5 μmol / g.

[0015] (3) In the temperature-induced desorption analysis of probe molecules using NH3, the amount of NH3 desorbed from peaks with peak temperatures below 300℃ (hereinafter also referred to as "low-temperature NH3 desorption amount") is above 25 μmol / g.

[0016] By satisfying one or more of the above conditions (1) to (3), there is a tendency for the amount of the target element retained per unit weight of the mesoporous alumina (adsorption amount) to increase. Therefore, by using the above adsorption method of the mesoporous alumina, the target element can be adsorbed efficiently.

[0017] In addition, according to this specification, a mesoporous alumina is provided that satisfies at least one of the following (1) to (3):

[0018] (1) The amount of surface hydroxyl groups is 3.5 mmol / g or more;

[0019] (2) In the temperature-dependent desorption analysis of probe molecules using CO2, the amount of CO2 desorbed from peaks with temperatures below 200℃ was greater than 5 μmol / g; and

[0020] (3) In the temperature-progression desorption analysis of probe molecules using NH3, the amount of NH3 desorbed from peaks with peak temperatures below 300℃ is above 25μmol / g.

[0021] The mesoporous alumina described above can efficiently adsorb the aforementioned target elements, and is therefore preferred. Detailed Implementation

[0022] The following describes suitable embodiments of the present invention. It should be noted that features other than those specifically mentioned in this specification, and features necessary for the implementation of the present invention, can be grasped by those skilled in the art based on prior art in this field. The present invention can be implemented based on the disclosures in this specification and common technical knowledge in this field.

[0023] The mesoporous alumina disclosed herein satisfies at least one of the following: the specified amount of surface hydroxyl groups, the specified low-temperature CO2 desorption amount, and the specified low-temperature NH3 desorption amount. It may be mesoporous alumina satisfying two or more of these conditions, or all three conditions.

[0024] In the aforementioned methods where the mesoporous alumina at least meets the specified surface hydroxyl content, the surface hydroxyl content of the mesoporous alumina can be 3.5 mmol / g or more. Mesoporous alumina meeting this surface hydroxyl content tends to retain a greater amount of adsorbed target elements per unit weight compared to mesoporous alumina with a lower surface hydroxyl content. In several methods, the aforementioned surface hydroxyl content is preferably 3.7 mmol / g or more, for example, 4.0 mmol / g or more, 4.5 mmol / g or more, or 5.0 mmol / g or more. There is no particular upper limit to the surface hydroxyl content, as long as it is an amount theoretically possible in relation to the specific surface area of ​​the mesoporous alumina. From the viewpoints of ease of manufacture, operability, storage, and quality stability, in several methods, the aforementioned surface hydroxyl content can be, for example, 20 mmol / g or less, 15 mmol / g or less, 10 mmol / g or less, 8 mmol / g or less, or 6 mmol / g or less.

[0025] The amount of surface hydroxyl groups referred to here can be determined by thermogravimetric-differential thermal analysis (TG-DTA), specifically by the following method. The same method is used for the examples described later.

[0026] [Method for determining the amount of surface hydroxyl groups]

[0027] The container containing the test sample and water is placed in a desiccator to allow water vapor to adsorb onto the hydroxyl groups present on the sample surface. After a sufficient time (preferably more than 3 hours), the sample is heated from room temperature to 200°C at a rate of 5°C / min using a thermogravimetric-differential thermal analysis (TGA) apparatus and held for 12 hours. The weight loss due to the desorption of physically adsorbed water from the sample is measured. Furthermore, the sample is heated to 900°C at a rate of 5°C / min and held for 12 hours. The amount of water lost due to the dehydration condensation of two adjacent hydroxyl groups is measured. Based on the results, the amount of surface hydroxyl groups [mmol / g] is calculated using the following formula.

[0028] Surface hydroxyl content [mmol / g] = 1.111 × ΔW2 / (1 - ΔW1 / 100)

[0029] Here, ΔW1 in the above formula represents the weight loss rate [wt%] after heating from room temperature to 200°C and holding at 200°C. ΔW2 in the above formula represents the weight loss rate [wt%] after heating from 200°C to 900°C and holding at 900°C.

[0030] In the aforementioned method where the mesoporous alumina at least meets the specified low-temperature CO2 desorption capacity, the low-temperature CO2 desorption capacity of the mesoporous alumina can be 5 μmol / g or more. Compared to mesoporous alumina with a lower low-temperature CO2 desorption capacity, mesoporous alumina that meets this low-temperature CO2 desorption capacity tends to retain a greater amount of the adsorbed element per unit weight. Among several methods, the aforementioned low-temperature CO2 desorption capacity is preferably 8 μmol / g or more, but can be 10 μmol / g or more, 12 μmol / g or more, 15 μmol / g or more, or 20 μmol / g or more. There is no particular upper limit to the low-temperature CO2 desorption capacity, as long as it is a theoretically achievable amount in relation to the specific surface area of ​​the mesoporous alumina. From the perspectives of ease of manufacture, operability, preservation, and quality stability, the aforementioned low-temperature CO2 desorption capacity can be, for example, below 400 μmol / g, below 300 μmol / g, below 250 μmol / g, below 200 μmol / g, below 100 μmol / g, below 70 μmol / g, below 50 μmol / g, below 30 μmol / g, below 20 μmol / g, or below 15 μmol / g in several methods.

[0031] The amount of CO2 desorption at low temperature mentioned here can be determined by temperature-progressive desorption analysis of CO2 using probe molecules (CO2-TPD), specifically by the following method. The same method is used for the examples described later.

[0032] [Method for determining low-temperature CO2 desorption capacity]

[0033] After placing the sample under reduced pressure (below 1 Pa) at 150°C for 10 hours, the sample was allowed to stand. CO2 gas was then introduced into a sample tube maintained at 40°C to allow CO2 to be fully adsorbed onto the sample. Excess CO2 was then purged using He gas under reduced pressure of approximately 3 kPa to approximately 10 kPa. Next, under reduced pressure and with He flow, the concentration of CO2 gradually desorbed at each temperature was measured using a quadrupole mass spectrometer. The resulting TPD desorption curves were separated into peaks, and the amount of CO2 desorbed from each peak was calculated based on its area. The amount of CO2 desorbed from the area of ​​peaks with temperatures below 200°C was taken as the low-temperature CO2 desorption amount of this sample. The quadrupole mass spectrometer can be the "OmniStar GSD301" (used in the examples described later) manufactured by Pfeiffer Vacuum GmbH or an equivalent.

[0034] Among the various methods of the technology disclosed herein, for the aforementioned mesoporous alumina, the amount of low-temperature CO2 desorption measured under reduced pressure by the method described above (hereinafter also referred to as "low-temperature CO2 desorption under reduced pressure") may be used instead of the amount of low-temperature CO2 desorption under reduced pressure, or the amount of CO2 desorption measured by the method described below (hereinafter also referred to as "low-temperature CO2 desorption under normal pressure") may be used in addition to the amount of low-temperature CO2 desorption under reduced pressure.

[0035] [Method for determining CO2 desorption at low temperature under normal pressure]

[0036] The sample was heated to 500°C at a rate of 10°C / hour under atmospheric pressure of approximately 1 atm and held for 60 minutes. After standing, CO2 gas was introduced into a sample tube maintained at 35°C to allow for sufficient CO2 adsorption. Excess CO2 was then purged using He gas at approximately 1 atm. Next, the temperature was increased to 500°C at a rate of 10°C / hour under He flow at approximately 1 atm, while the concentration of gradually desorbed CO2 at each temperature was measured using a quadrupole mass spectrometer. The resulting TPD desorption curve was subjected to peak separation, and the amount of CO2 desorbed from each peak was calculated based on its area. The amount of CO2 desorbed from the area of ​​peaks with temperatures below 200°C was taken as the low-temperature CO2 desorption amount at atmospheric pressure for this sample. The quadrupole mass spectrometer could be the MKS Cirrus 2 (used in the examples described later) from MKS Instruments UK Ltd., or an equivalent.

[0037] The low-temperature CO2 desorption capacity of mesoporous alumina under ambient pressure can be, for example, 5 μmol / g or more, 10 μmol / g or more, 20 μmol / g or more, or 30 μmol / g or more. As the low-temperature CO2 desorption capacity under ambient pressure increases, there is a tendency for the amount of adsorbed element (e.g., Mo) retained per unit weight of mesoporous alumina to increase. From this perspective, among several approaches, a low-temperature CO2 desorption capacity of mesoporous alumina under ambient pressure of 35 μmol / g or more is advantageous, 45 μmol / g or more is favorable, 55 μmol / g or more is preferred, and it can also be 75 μmol / g or more, 95 μmol / g or more, 110 μmol / g or more, 130 μmol / g or more, 140 μmol / g or more, or 150 μmol / g or more. There is no particular upper limit to the low-temperature CO2 desorption capacity under ambient pressure, as long as it is a theoretically achievable amount in relation to the specific surface area of ​​the mesoporous alumina. From the perspectives of ease of manufacture, operability, preservation, and quality stability, the CO2 desorption capacity at low temperature under normal pressure can be, for example, below 400 μmol / g, below 300 μmol / g, below 250 μmol / g, below 230 μmol / g, or below 200 μmol / g in several methods.

[0038] In the aforementioned method where the mesoporous alumina at least meets the specified low-temperature NH3 desorption capacity, the low-temperature NH3 desorption capacity of the mesoporous alumina can be 25 μmol / g or more. Compared to mesoporous alumina with a lower low-temperature NH3 desorption capacity, mesoporous alumina that meets this low-temperature NH3 desorption capacity tends to retain a greater amount of the adsorbed element per unit weight. Among several methods, the aforementioned low-temperature NH3 desorption capacity is preferably 30 mol / g or more, 40 μmol / g or more, 50 μmol / g or more, 60 μmol / g or more, or 70 μmol / g or more. There is no particular upper limit to the low-temperature NH3 desorption capacity, as long as it is a theoretically achievable amount in relation to the specific surface area of ​​the mesoporous alumina. For example, the low-temperature NH3 desorption capacity of the mesoporous alumina can be 700 μmol / g or less, 500 μmol / g or less, or 400 μmol / g or less. From the perspectives of ease of manufacture, operability, preservation, and quality stability, the low-temperature NH3 desorption capacity of mesoporous alumina can be, for example, below 300 μmol / g, below 200 μmol / g, below 150 μmol / g, below 100 μmol / g, below 80 μmol / g, or below 60 μmol / g in several ways.

[0039] The amount of NH3 desorption at low temperature mentioned here can be determined by temperature-progressive desorption analysis of NH3 using probe molecules (NH3-TPD), specifically by the following method. The same method is used for the examples described later.

[0040] [Method for determining the amount of NH3 desorption at low temperature]

[0041] After placing the sample at 150°C under reduced pressure (below 1 Pa) for 10 hours, the sample was allowed to stand. An NH3 / He mixed gas was then introduced into a sample tube maintained at 40°C to allow NH3 to be fully adsorbed onto the sample. The sample was then replaced with He gas, and excess NH3 was purged under reduced pressure (approximately 3 kPa to approximately 10 kPa). Next, under reduced pressure and with He flow, the temperature was increased at a rate of 10°C / min, and the concentration of NH3 gradually desorbed at each temperature was measured using a quadrupole mass spectrometer. The resulting TPD desorption curves were separated into peaks, and the amount of NH3 desorbed from each peak was calculated based on its area. The amount of NH3 desorbed from the area of ​​peaks with temperatures below 300°C was taken as the low-temperature NH3 desorption amount of this sample. The quadrupole mass spectrometer can be a Pfeiffer Vacuum GmbH model “OmniStar GSD301” (used in the examples described later) or an equivalent.

[0042] In the technology disclosed herein, the specific surface area of ​​mesoporous alumina is not particularly limited. For example, the specific surface area can be approximately 50 m². 2 / g or more. Among several methods, from the viewpoint of increasing the contact area with the adsorbed element, the aforementioned specific surface area can be approximately 100m². 2 / g or more is advantageous, with approximately 130m being preferred. 2 / g or more, more preferably approximately 150m 2 / g or more, can be approximately 190m 2 / g or more, can be approximately 220m 2 / g or more. Furthermore, from the viewpoint of the strength and durability of mesoporous alumina, in several ways, the aforementioned specific surface area can, for example, be approximately 500 m². 2 Below / g, it can be approximately 400m 2 Below / g, it can be approximately 300m 2 Below / g, it can be approximately 270m 2 Below / g, it can be approximately 220m 2 / g or less. The specific surface area can be determined by the nitrogen adsorption capacity determination method (BET method). The same method is also used for the examples described later.

[0043] In the technology disclosed herein, the average pore size of the mesoporous alumina is not particularly limited, typically ranging from approximately 2 nm to approximately 50 nm. In several embodiments, from the viewpoint of facilitating the achievement of the aforementioned specific surface area, an average pore size of approximately 40 nm or less is suitable, preferably approximately 30 nm or less, more preferably approximately 25 nm or less, and can be approximately less than 20 nm, approximately less than 15 nm, approximately less than 13 nm, approximately less than 11 nm, or approximately less than 9 nm. Furthermore, in several embodiments, from the viewpoint of contact efficiency with the adsorbed element, the average pore size of approximately 4 nm or more is suitable, preferably approximately 6.5 nm or more, approximately 8 nm or more, approximately 10 nm or more, approximately 13 nm or more, or approximately 16 nm or more. The average pore size can be determined using the nitrogen adsorption capacity determination method (BJH method). The same method is also used for the embodiments described later.

[0044] In the techniques disclosed herein, the pore volume of mesoporous alumina is not particularly limited. In several approaches, from the viewpoint of contact efficiency with the target adsorbed element, the aforementioned pore volume is approximately 0.2 cm³. 3 / g or more is appropriate, preferably around 0.4cm 3 / g or more, more preferably approximately 0.5cm 3 / g or more, can be approximately 0.7cm 3 / g or more, can be approximately 1.1cm 3 / g or more. Furthermore, from the viewpoint of the strength and durability of mesoporous alumina, in several methods, the aforementioned pore volume can be, for example, approximately 3.0 cm³. 3 Below / g, it can be approximately 2.2cm. 3 Below / g, it can be approximately 1.7cm. 3 Below / g, it can be approximately 1.2cm. 3 Below / g, it can be approximately 0.8cm 3 / g or less. The pore volume can be determined using the nitrogen adsorption capacity determination method. The same method is used for the examples described later.

[0045] For the mesoporous alumina disclosed herein, from the perspective of easily increasing the retention of adsorbed target elements per unit weight, calcination is preferably carried out in a manner that produces γ-alumina (sometimes referred to as activated alumina). The mesoporous alumina being γ-alumina can be confirmed, for example, by X-ray diffraction.

[0046] The method for manufacturing mesoporous alumina disclosed herein is not particularly limited. Those skilled in the art, based on one or more known techniques, can appropriately select the manufacturing method, choose the materials used, and set the manufacturing or processing conditions to manufacture mesoporous alumina that satisfies one, two, or three of the specified surface hydroxyl content, specified low-temperature CO2 desorption amount under reduced pressure (or specified low-temperature CO2 desorption amount under normal pressure), and specified low-temperature NH3 desorption amount disclosed herein. This allows for the preparation of mesoporous alumina for use in any of the adsorption methods disclosed herein.

[0047] Examples of the aforementioned known technologies include the following steps: drying a slurry prepared by mixing an aluminum source, a pore-forming agent, and an aqueous solvent to obtain an alumina precursor; calcining the obtained alumina precursor; calcining alumina sol and alumina hydrate; removing surfactant micelles from the alumina precursor obtained by the sol-gel method using a pore-forming template, using calcination, washing, or other methods; manufacturing using an evaporation-induced self-assembly method; etc., but are not limited to these steps. The calcination is preferably performed in a manner that produces γ-alumina. For example, a calcination temperature of approximately 500°C or higher and approximately 800°C or lower (more preferably approximately 550°C or higher and approximately 700°C or lower, or approximately 650°C or higher and approximately 750°C or lower) is preferably used.

[0048] As the aluminum source, an organoaluminum compound or its hydrolysate can be used. Examples of the organoaluminum compound include, for example, aluminum alkoxides such as aluminum isopropoxide. Examples of the pore-forming agent or template include inorganic compounds that decompose to produce gas upon heating below the firing temperature (preferably compounds belonging to at least one of ammonium salts, carbonates, and bicarbonates; examples include ammonium carbonate, ammonium bicarbonate, and sodium bicarbonate), and organic compounds that can be decomposed and removed upon heating (e.g., polymers such as glucose, polymer nanospheres such as polydiaminopyridine nanospheres), but these are not limited to these. The amount of the pore-forming agent (e.g., the inorganic compound) used relative to 100 parts by weight of the aluminum source (e.g., aluminum alkoxide) can be, for example, 50 parts by weight or more, preferably 100 parts by weight or more.

[0049] The adsorption method disclosed herein includes the following steps: preparing mesoporous alumina that meets one, two, or three of the following specified requirements: surface hydroxyl content, low-temperature CO2 desorption capacity under reduced pressure (or low-temperature CO2 desorption capacity under normal pressure), and low-temperature NH3 desorption capacity; and contacting a liquid containing the target element with the mesoporous alumina. The above adsorption method can preferably be implemented using the mesoporous alumina disclosed herein. By contacting the liquid containing the target element with the mesoporous alumina, the target element contained in the liquid can be adsorbed onto the mesoporous alumina. Here, the adsorption of the target element onto the mesoporous alumina can also be controlled by using the mesoporous alumina to remove or separate the target element. Therefore, the matters disclosed in this specification include: techniques for adsorbing, separating, or removing target elements using mesoporous alumina.

[0050] The adsorption target element is selected from at least one element chosen from the group consisting of elements belonging to periods 4 to 6 and groups 3 to 15 of the periodic table. In several embodiments, the adsorption target element may be an element belonging to periods 4 to 6 (e.g., periods 4 to 5) and groups 4 to 15 of the periodic table; an element belonging to periods 4 to 6 (e.g., periods 4 to 5) and groups 3 to 14; an element belonging to periods 4 to 6 (e.g., periods 4 to 5) and groups 4 to 14; or an element belonging to periods 4 to 6 (e.g., periods 4 to 5) and groups 4 to 12. Additionally, in several embodiments, the adsorption target element may be an element belonging to period 4 and groups 3 to 15 (preferably groups 4 to 14, e.g., groups 4 to 12) of the periodic table; or an element belonging to period 5 and groups 3 to 15 (preferably groups 4 to 14, e.g., groups 4 to 12). Specific examples of elements that can be adsorbed in the adsorption methods disclosed herein include, but are not limited to, Ti, Cr, Co, Ni, Cu, Zn, Zr, Mo, and Pb.

[0051] The content of the target element in the liquid is not particularly limited. In several ways, the content of the target element can be, for example, greater than 0 g / L and less than 20 g / L. The mesoporous alumina disclosed herein is also preferably used for adsorbing the target element from a liquid containing the target element at a content of, for example, less than 20,000 ppm, less than 10,000 ppm, or less than 5,000 ppm. The content of the target element can be, for example, more than 1 ppm, more than 10 ppm, or more than 100 ppm.

[0052] The pH of the liquid containing the target element is not particularly limited, and can be, for example, around 2 to 12, 2 to 10, or 2 to 8. The techniques disclosed herein are preferably used for liquids containing the target element with a pH of 2 to 6. From the viewpoint of the durability of mesoporous alumina, a pH of approximately 2.5 or higher for the liquid containing the target element is advantageous. In several cases, the pH can be 3 or higher, 4 or higher, or 4.5 or higher. In other cases, the pH can be 5.5 or lower, 4 or lower, or 3 or lower. To adjust the pH of the liquid containing the target element, an appropriate amount of pH adjuster can be used as needed. Examples of such pH adjusters include potassium hydroxide, sodium hydroxide, hydrochloric acid, nitric acid, and sulfuric acid, but are not limited to these. A single pH adjuster can be used alone, or a suitable combination of two or more can be used.

[0053] The temperature of the liquid containing the target adsorbent element in contact with the mesoporous alumina is not particularly limited; for example, it can be around 0°C to 60°C. In several preferred embodiments, the temperature of the liquid containing the target adsorbent element can be above 10°C, above 20°C, below 50°C, or below 40°C. From the viewpoint of ease of operation, contact at room temperature (typically 20°C to 30°C) is preferred.

[0054] There are no particular limitations on the method of contacting the liquid containing the target adsorbent element with the mesoporous alumina; for example, contact can be achieved by liquid flow or immersion. Liquid flow can be carried out in a single pass or by circulating the liquid containing the target adsorbent element.

[0055] The mesoporous alumina disclosed herein, in addition to its adsorption applications for target elements, can also be preferably used in various fields and for various other applications. Examples of applications of the mesoporous alumina disclosed herein include: metal ion adsorption materials, metal ion separation materials, liquid adsorption materials, liquid filtration materials, liquid separation materials, gas adsorption materials, gas filtration materials, gas separation materials, water-absorbing materials, water-retaining materials, humidity control materials, drainage treatment materials, carriers for fragrances / deodorization, food refining / sterilizing materials, materials for separating / concentrating microorganisms such as pharmaceutical microorganisms, carriers for drug delivery, materials for cosmetics, catalyst carriers, materials for bioreactors / microorganisms, materials for humidity sensors, sound-absorbing / sound-insulating materials, heat-insulating materials, and heat-shielding materials, but are not limited to these. The matters disclosed in this specification include the use of mesoporous alumina in any of the above-mentioned applications and the use of mesoporous alumina in the above-mentioned applications.

[0056] The following matters are among the matters disclosed in this specification.

[0057] [1] An adsorption method for elements belonging to periods 4 to 6 and groups 3 to 15 of the periodic table, the adsorption method comprising the following steps:

[0058] Prepare mesoporous alumina that meets at least one of the following (1) to (3):

[0059] (1) The amount of surface hydroxyl groups determined by the following method is 3.5 mmol / g or more;

[0060] (2) The CO2 desorption capacity under reduced pressure at low temperature, as determined by the following method, is 5 μmol / g or higher; and

[0061] (3) The low-temperature NH3 desorption capacity, as determined by the following method, is 25 μmol / g or higher; and,

[0062] The liquid containing the target element is brought into contact with the mesoporous alumina, causing the target element to be adsorbed onto the mesoporous alumina.

[0063] The adsorption target element is selected from at least one element in the group consisting of elements belonging to the 4th to 6th periods and the 3rd to 15th groups of the periodic table.

[0064] [Method for determining the amount of surface hydroxyl groups]

[0065] The container containing the test sample and water is placed in a desiccator to allow water vapor to adsorb onto the hydroxyl groups present on the sample surface. After a sufficient time (preferably more than 3 hours), the sample is heated from room temperature to 200°C at a rate of 5°C / min using a thermogravimetric-differential thermal analysis (TGA) apparatus and held for 12 hours. The weight loss due to the desorption of physically adsorbed water from the sample is measured. Furthermore, the sample is heated to 900°C at a rate of 5°C / min and held for 12 hours. The amount of water lost due to the dehydration condensation of two adjacent hydroxyl groups is measured. Based on the results, the amount of surface hydroxyl groups [mmol / g] is calculated using the following formula.

[0066] Surface hydroxyl content [mmol / g] = 1.111 × ΔW2 / (1 - ΔW1 / 100)

[0067] [Method for determining CO2 desorption at low temperature under reduced pressure]

[0068] After placing the sample under reduced pressure (below 1 Pa) at 150°C for 10 hours, the sample was allowed to stand. CO2 gas was then introduced into a sample tube maintained at 40°C to allow CO2 to be fully adsorbed onto the sample. Excess CO2 was then purged using He gas under reduced pressure (approximately 3 kPa to approximately 10 kPa). Next, under reduced pressure and with He flow, the temperature was increased at 5°C / min, and the concentration of gradually desorbed CO2 at each temperature was measured using a quadrupole mass spectrometer. The resulting TPD desorption curves were subjected to peak separation, and the amount of CO2 desorbed from each peak was calculated based on its area. The amount of CO2 desorbed from the area of ​​peaks with temperatures below 200°C was taken as the low-temperature CO2 desorption amount of this sample under reduced pressure.

[0069] [Method for determining the amount of NH3 desorption at low temperature]

[0070] After placing the sample at 150°C under reduced pressure (below 1 Pa) for 10 hours, the sample was allowed to stand. An NH3 / He mixed gas was then introduced into a sample tube maintained at 40°C to allow NH3 to be fully adsorbed onto the sample. The sample was then replaced with He gas, and excess NH3 was purged under reduced pressure (approximately 3 kPa to approximately 10 kPa). Next, under reduced pressure and with He flowing through the sample, the temperature was increased at a rate of 10°C / min, and the concentration of NH3 gradually desorbed at each temperature was measured using a quadrupole mass spectrometer. The resulting TPD desorption curves were subjected to peak separation, and the amount of NH3 desorbed from each peak was calculated based on its area. The amount of NH3 desorbed from the area of ​​peaks with temperatures below 300°C was taken as the low-temperature NH3 desorption amount of this sample.

[0071] [2] According to the method described in [1] above, mesoporous alumina is prepared to at least satisfy the above (2) as the above mesoporous alumina.

[0072] [3] According to the method described in [1] above, mesoporous alumina is prepared to satisfy at least the above (2) and the following (4):

[0073] (4) The amount of CO2 desorption at low temperature under normal pressure, as determined by the following method, is 5 μmol / g or more (e.g., 35 μmol / g or more).

[0074] [Method for determining CO2 desorption at low temperature under normal pressure]

[0075] The sample was heated to 500°C at a rate of 10°C / hour under atmospheric pressure (approximately 1 atm) and held for 60 minutes. After standing, CO2 gas was introduced into a sample tube maintained at 35°C to allow for complete CO2 adsorption. Excess CO2 was then purged using He gas at approximately 1 atm. Next, the sample was heated to 500°C at a rate of 10°C / hour under He flow while simultaneously measuring the concentration of gradually desorbed CO2 at each temperature using a quadrupole mass spectrometer. The resulting TPD desorption curves were subjected to peak separation, and the amount of CO2 desorbed from each peak was calculated based on its area. The amount of CO2 desorbed from the area of ​​peaks with temperatures below 200°C was taken as the low-temperature CO2 desorption amount of this sample at atmospheric pressure.

[0076] [4] An adsorption method for elements belonging to periods 4 to 6 and groups 3 to 15 of the periodic table, the adsorption method comprising the following steps:

[0077] Prepare mesoporous alumina that meets at least one of the following (1), (3), and (4):

[0078] (1) The amount of surface hydroxyl groups measured by the method described in [1] above is 3.5 mmol / g or more;

[0079] (3) The amount of NH3 desorption at low temperature, determined by the method described in [1] above, is 25 μmol / g or more; and

[0080] (4) The amount of CO2 desorption at ambient pressure at low temperature, as determined by the following method, is 5 μmol / g or more (e.g., 35 μmol / g or more); and,

[0081] The liquid containing the target element is brought into contact with the mesoporous alumina, causing the target element to be adsorbed onto the mesoporous alumina.

[0082] The adsorption target element is selected from at least one element in the group consisting of elements belonging to the 4th to 6th periods and the 3rd to 15th groups of the periodic table.

[0083] [Method for determining CO2 desorption at low temperature under normal pressure]

[0084] The sample was heated to 500°C at a rate of 10°C / hour under atmospheric pressure (approximately 1 atm) and held for 60 minutes. After standing, CO2 gas was introduced into a sample tube maintained at 35°C to allow for complete CO2 adsorption. Excess CO2 was then purged using He gas at approximately 1 atm. Next, the sample was heated to 500°C at a rate of 10°C / hour under He flow while simultaneously measuring the concentration of gradually desorbed CO2 at each temperature using a quadrupole mass spectrometer. The resulting TPD desorption curves were subjected to peak separation, and the amount of CO2 desorbed from each peak was calculated based on its area. The amount of CO2 desorbed from the area of ​​peaks with temperatures below 200°C was taken as the low-temperature CO2 desorption amount of this sample at atmospheric pressure.

[0085] [5] According to the method described in [4] above, mesoporous alumina is prepared to at least satisfy the above (4) as the above mesoporous alumina.

[0086] [6] According to any one of [1] to [5] above, wherein the mesoporous alumina has a density of 100 μm 2 Specific surface area above / g.

[0087] [7] The method according to any one of [1] to [6] above, wherein the mesoporous alumina has an average pore size of 2 nm or more and 30 nm or less.

[0088] [8] The method according to any one of [1] to [7] above, wherein the pH of the liquid containing the adsorbed target element is 2 to 6.

[0089] [9] A mesoporous alumina used in any one of [1] to [8] above.

[0090]

[10] A mesoporous alumina for adsorbing elements belonging to periods 4 to 6 and groups 3 to 15 of the periodic table, and satisfying at least one of the following (1) to (3):

[0091] (1) The amount of surface hydroxyl groups measured by the method described in [1] above is 3.5 mmol / g or more;

[0092] (2) The amount of CO2 desorption under reduced pressure at low temperature, as determined by the method described in [1] above, is 5 μmol / g or more; and

[0093] (3) The amount of NH3 desorption at low temperature determined by the method described in [1] above is 25 μmol / g or more.

[0094]

[11] The mesoporous alumina described in

[10] above satisfies at least the above (2).

[0095]

[12] The mesoporous alumina described in

[11] above satisfies at least the above (2) and the following (4):

[0096] (4) The amount of CO2 desorption at low temperature under normal pressure, as determined by the method described in [4] above, is 5 μmol / g or more (e.g., 35 μmol / g or more).

[0097]

[13] A mesoporous alumina for adsorbing elements belonging to periods 4 to 6 and groups 3 to 15 of the periodic table, and satisfying at least one of the following (1), (3), and (4):

[0098] (1) The amount of surface hydroxyl groups measured by the method described in [1] above is 3.5 mmol / g or more;

[0099] (3) The amount of NH3 desorption at low temperature, determined by the method described in [1] above, is 25 μmol / g or more; and

[0100] (4) The amount of CO2 desorption at low temperature under normal pressure, as determined by the method described in [4] above, is 5 μmol / g or more (e.g., 35 μmol / g or more).

[0101]

[14] The mesoporous alumina described in

[13] above satisfies at least the above (4).

[0102]

[15] Mesoporous alumina according to any one of

[10] to

[14] above, wherein the mesoporous alumina has a density of 100 μm. 2 Specific surface area above / g.

[0103]

[16] The mesoporous alumina according to any one of

[10] to

[15] above, wherein the mesoporous alumina has an average pore size of 2 nm or more and 30 nm or less.

[0104] Example

[0105] The following describes several embodiments of the present invention, but it is not intended to limit the present invention to the solutions shown in the specific examples above.

[0106] <<Experimental Example 1>>

[0107] <Preparation of Mesoporous Alumina>

[0108] (Preparation Example 1)

[0109] At room temperature, 970g of distilled water was added to a container, and 60g of ammonium carbonate was added while stirring until dissolved. Then, 32g of powdered aluminum isopropoxide was added, and the mixture was stirred continuously at room temperature for 24 hours to prepare an intermediate solution. This intermediate solution was transferred to a heat-resistant container and dried at 80°C for 48 hours to obtain alumina precursor powder. This powder was then calcined in an atmospheric furnace at 700°C for 5 hours, and then crushed to pass through a 50-mesh metal mesh. This process yielded mesoporous alumina (specific surface area 219 m²) for Sample 1. 2 / g, pore volume 1.63cm 3 / g, average pore size 11.1nm).

[0110] (Preparation Example 2)

[0111] The amount of ammonium carbonate was changed to 30g. Otherwise, similarly to the preparation of mesoporous alumina in Sample 1, mesoporous alumina (specific surface area 224m²) was prepared in Sample 2. 2 / g, pore volume 0.61cm 3 / g, average pore size 9.6nm).

[0112] (Preparation Example 3)

[0113] Commercially available alumina sol (manufactured by Nissan Chemical Co., Ltd., AS-200) was calcined at 700°C for 5 hours in an atmospheric furnace, and then crushed to pass through a 50-mesh metal mesh. This process yielded mesoporous alumina (specific surface area 204 m²) for sample 3. 2 / g, pore volume 0.49cm 3 / g, average pore size 8.3nm).

[0114] As sample 4, commercially available mesoporous alumina (Sigma Aldrich, product number 199966, Brockmann activity I, specific surface area 154 m²) was used. 2 / g, pore volume 0.25cm 3 / g, average pore size 6nm).

[0115] <Determination of surface hydroxyl content, low-temperature CO2 desorption under reduced pressure, and low-temperature NH3 desorption>

[0116] The surface hydroxyl content (S) of samples 1 to 4 was determined according to the above method. OH ), Low-temperature CO2 desorption capacity under reduced pressure (L) CO2 ) and low-temperature NH3 desorption capacity (L NH3 The results are shown in Table 1.

[0117] <Adsorption Experiment (Implementation of Adsorption Method)>

[0118] Mesoporous alumina samples 1–4 were packed into a column with a diameter of 4.6 mm and a length of 50 mm. At room temperature, a liquid containing Mo, the target adsorbent element, was pumped through the column at a rate of 5 mL / min. The Mo concentration in the liquid before and after passing through the column was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). The Mo retention [mg / g] was calculated by converting the Mo reduction relative to the pre- and post-passage values ​​to a value per 1 g of sample. A 0.25 wt% sodium molybdate aqueous solution was used as the liquid passing through the column, with the pH adjusted to 2.5 using nitric acid (Mo concentration 900 ppm). The results are shown in Table 1.

[0119] [Table 1]

[0120] surface"

[0121]

[0122] It should be noted that, for the samples obtained above, the CO2 desorption capacity at ambient pressure was determined using the above method. The results were 167.0 μmol / g for sample 1 and 146.6 μmol / g for sample 3. Furthermore, the CO2 desorption capacity of sample 4 at ambient pressure was significantly lower than that of samples 1 and 3. As these results and the Mo retention values ​​of each sample shown in Table 1 indicate, a positive correlation was confirmed between the CO2 desorption capacity at ambient pressure and the Mo retention value. In the above adsorption experiments, even when the pH of the liquid passing through the column was changed to 2.0, the same correlation was confirmed between the CO2 desorption capacity at ambient pressure and the Mo retention value.

[0123] <<Experimental Example 2>>

[0124] For samples 1, 3, and 4 used in the adsorption experiment of Experimental Example 1, Zr, Co, Cr, Cu, Ni, and Zu were used as target elements, and the same adsorption experiments were conducted to determine the retention amount of each metal element. The liquid containing the target element passing through the column was an ICP standard solution (Merck) containing each element at a concentration of approximately 1000 ppm, with the pH adjusted to 2.5 or 5 using KOH. The results are shown in Table 2. It should be noted that N / A in Table 2 indicates that the experiment was not performed.

[0125] [Table 2]

[0126] Table 2

[0127]

[0128] The specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations to the specific examples described above.

Claims

1. An adsorption method for elements belonging to periods 4 to 6 and groups 3 to 15 of the periodic table, the adsorption method comprising the following steps: Prepare mesoporous alumina that meets at least one of the following (1) to (3) and has an average pore size of 6.5 nm or more and 50 nm or less: (1) The amount of surface hydroxyl groups is 3.5 mmol / g or more; (2) In the temperature-dependent desorption analysis of probe molecules using CO2, the amount of CO2 desorbed from peaks with temperatures below 200℃ is greater than 5 μmol / g; and (3) In the temperature-progression desorption analysis of probe molecules using NH3, the amount of NH3 desorbed from peaks with peak temperatures below 300℃ is greater than 25 μmol / g; and, The liquid containing the target element is brought into contact with the mesoporous alumina, causing the target element to be adsorbed onto the mesoporous alumina. The adsorption target element is selected from at least one element in the group consisting of elements belonging to the 4th to 6th periods and the 3rd to 15th groups of the periodic table.

2. The method according to claim 1, wherein, The mesoporous alumina has a density of 100m 2 Specific surface area above / g.

3. The method according to claim 1 or 2, wherein, The mesoporous alumina has an average pore size of 6.5 nm or more and 30 nm or less.

4. The method according to claim 1 or 2, wherein, The pH of the liquid containing the adsorbed element is 2 to 6.

5. A mesoporous alumina for adsorbing elements belonging to periods 4 to 6 and groups 3 to 15 of the periodic table, and satisfying at least one of the following (1) to (3): (1) The amount of surface hydroxyl groups is 3.5 mmol / g or more; (2) In the temperature-dependent desorption analysis of probe molecules using CO2, the amount of CO2 desorbed from peaks with temperatures below 200℃ is greater than 5 μmol / g; and (3) In the temperature-progression desorption analysis of probe molecules using NH3, the amount of NH3 desorbed from peaks with peak temperatures below 300℃ is above 25 μmol / g. The mesoporous alumina has an average pore size of 6.5 nm or more and 50 nm or less.

6. The mesoporous alumina according to claim 5, wherein, The mesoporous alumina has a density of 100m 2 Specific surface area above / g.

7. The mesoporous alumina according to claim 5 or 6, wherein, The mesoporous alumina has an average pore size of 6.5 nm or more and 30 nm or less.

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