Absorption method and mesoporous alumina used for the same

Abstract

Provided is an absorption method of an element belonging to periods 4 to 6 and groups 3 to 15 of the periodic table. The method includes: preparing mesoporous alumina that satisfies at least one of the following items: (1) a surface hydroxyl content is 3.5 mmol / g or more; (2) a low-temperature CO₂ desorption amount in CO₂ thermal desorption amount spectrometry is 5 μmol / g or more; and (3) a low-temperature NH3 desorption amount in NH3 thermal desorption amount spectrometry is 25 μmol / g or more; and bringing a liquid containing an absorption target element in contact with the mesoporous alumina to absorb the absorption target element in the mesoporous alumina. The absorption target element is at least one type selected from the group consisting of an element belonging to periods 4 to 6 and groups 3 to 15 of the periodic table.

Description

Adsorption method and mesoporous alumina used in the method

[0001] The present invention relates to an adsorption method and a mesoporous alumina for use in the method. This application claims priority to U.S. Provisional Patent Application No. 63 / 061,956, filed August 6, 2020, the entire contents of which are incorporated herein by reference.

[0002] It is known to use porous metal oxides as adsorbents or catalyst carriers. For example, Patent Document 1 relates to a technology for adsorbing and removing radioactive cesium and strontium from natural water or contaminated water, and proposes a cesium / strontium adsorbent made of porous glass by a phase separation method and a system for forming a stable vitrified body after adsorption. Furthermore, Patent Document 2 states: ９９ｍ This paper describes a porous metal oxide useful as a molybdenum (Mo) adsorbent for Tc generators and a method for producing the same.

[0003] Japanese Patent Application Publication No. 2019-000764 International Publication No. 2017 / 126602

[0004] The technology described in Patent Document 1 is mostly based on SiO ２ The patent document presupposes the use of a phase-separation porous glass composed of the above (e.g., Claim 1, paragraph

[0051] ), and does not use an adsorbent mainly composed of alumina. Furthermore, in Patent Document 1, the elements to be adsorbed by the adsorbent (elements to be adsorbed) are limited to cesium and strontium, and the adsorption of other elements is not intended. Patent Document 2 focuses on the manufacturing method and structural characteristics (specific surface area, pore volume, average pore diameter, etc.) of porous metal oxides with regard to the Mo retention capacity of porous alumina and other metal oxides, but does not specifically consider the retention of elements other than Mo. It would be beneficial to provide an adsorption method using an adsorbent that is applicable to the adsorption of Groups 3 to 15 of the periodic table other than Mo.

[0005] The present invention aims to provide an adsorption method that solves the above problems. Another related object is to provide an adsorbent suitable for carrying out the above adsorption method.

[0006] According to this specification, a method for adsorbing elements belonging to Periods 4 to 6 and Groups 3 to 15 of the periodic table is provided. The adsorption method includes preparing mesoporous alumina and contacting the mesoporous alumina with a liquid containing the element to be adsorbed, thereby adsorbing the element to be adsorbed onto the mesoporous alumina. The element to be adsorbed is at least one element 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 (1) to (3): (1) The amount of surface hydroxyl groups is 3.5 mmol / g or more. (2) CO ２ In thermal desorption analysis using as a probe molecule, CO desorbed at a peak temperature of less than 200°C ２ amount (hereinafter referred to as “low-temperature CO ２ (3) NH ３ In thermal desorption analysis using as a probe molecule, NH desorbed at a peak temperature of less than 300°C ３ amount (hereinafter referred to as “low temperature NH ３ The amount of desorption (also referred to as "amount of desorption") is 25 μmol / g or more.

[0007] By satisfying one or more of the above conditions (1) to (3), the amount of the target element to be adsorbed (the amount of adsorption) per unit weight of the mesoporous alumina tends to increase, and therefore, the adsorption method using such mesoporous alumina can efficiently adsorb the target element to be adsorbed.

[0008] According to this specification, the following (1) to (3) are stated: (1) the amount of surface hydroxyl groups is 3.5 mmol / g or more; (2) CO ２ In thermal desorption analysis using as a probe molecule, CO desorbed at a peak temperature of less than 200°C ２ (3) NH ３ In thermal desorption analysis using as a probe molecule, NH desorbed at a peak temperature of less than 300°C ３The amount of the adsorbed element is 25 μmol / g or more. Such mesoporous alumina is preferable because it can efficiently adsorb the adsorbed element.

[0009] Preferred embodiments of the present invention will be described below. It should be noted that matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field.

[0010] The mesoporous alumina in the technology disclosed herein has a predetermined amount of surface hydroxyl groups, which will be explained below, and a predetermined low-temperature CO ２ Desorption amount and predetermined low-temperature NH ３ The mesoporous alumina may satisfy two or more of these requirements, or may satisfy all three of these requirements.

[0011] In embodiments where the mesoporous alumina satisfies at least a predetermined surface hydroxyl group content, the surface hydroxyl group content of the mesoporous alumina may be 3.5 mmol / g or more. Mesoporous alumina satisfying this surface hydroxyl group content tends to retain a greater amount of the adsorbed element per unit weight than mesoporous alumina with a lower surface hydroxyl group content. In some embodiments, the surface hydroxyl group content is preferably 3.7 mmol / g or more, for example, 4.0 mmol / g or more, 4.5 mmol / g or more, or even 5.0 mmol / g or more. The upper limit of the surface hydroxyl group content is not particularly limited, and may be any amount that can theoretically exist in relation to the specific surface area of ​​the mesoporous alumina. From the viewpoints of ease of production, handleability, storage stability, quality stability, and the like, in some embodiments, the surface hydroxyl group content may 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.

[0012] The amount of surface hydroxyl groups referred to here can be determined by thermogravimetry-differential thermal analysis (TG-DTA), and is specifically measured by the following method. A similar method is also used in the examples described below. [Method for Measuring the Amount of Surface Hydroxyl Groups] A container containing the sample to be measured and water is placed in a desiccator, and water vapor is allowed to adsorb to the hydroxyl groups present on the sample surface. After a sufficient amount of time (preferably 3 hours or more) has passed, the sample is heated from room temperature to 200°C at a rate of 5°C / min and then held for 12 hours using a thermogravimetry-differential thermal analyzer, and the weight loss due to 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 then held for 12 hours, and the amount of water removed by dehydration condensation of two adjacent hydroxyl groups is measured. From the obtained results, the amount of surface hydroxyl groups [mmol / g] is calculated using the following formula: Amount of surface hydroxyl groups [mmol / g] = 1.111 × ΔW2 / (1 - ΔW1 / 100)

[0013] Here, ΔW1 in the above formula represents the weight loss rate [wt %] after the temperature is increased from room temperature to 200° C. and held at 200° C. ΔW2 in the above formula represents the weight loss rate [wt %] after the temperature is increased from 200° C. to 900° C. and held at 900° C.

[0014] The mesoporous alumina is at least ２ In an embodiment satisfying the desorption amount, the low-temperature CO ２ The desorption amount can be 5 μmol / g or more. ２ Mesoporous alumina that satisfies the desorption amount can desorb CO at lower temperatures. ２ The amount of the adsorbed element retained per unit weight tends to be larger than that of mesoporous alumina, which desorbs a smaller amount. ２ The desorption amount is preferably 8 μmol / g or more, and may be 10 μmol / g or more, 12 μmol / g or more, 15 μmol / g or more, or 20 μmol / g or more. ２The upper limit of the desorption amount is not particularly limited, and may be any amount that is theoretically possible in relation to the specific surface area of ​​the mesoporous alumina. ２ The amount of desorption may be, for example, 400 μmol / g or less, 300 μmol / g or less, 250 μmol / g or less, 200 μmol / g or less, 100 μmol / g or less, 70 μmol / g or less, 50 μmol / g or less, 30 μmol / g or less, 20 μmol / g or less, or 15 μmol / g or less.

[0015] Here, low-temperature CO ２ The amount of desorption is CO ２ Thermal desorption spectrometry (TDS) using CO as a probe molecule ２ -TPD), which is specifically measured by the following method. The same method is also used in the examples described later. ２ Measurement method for the amount of desorption] A sample to be measured is left under reduced pressure (1 Pa or less) at 150°C for 10 hours, and then the sample is left to stand and CO is added to a sample tube maintained at 40°C. ２ CO gas is passed through the sample. ２ After that, excess CO was removed by using He gas under a reduced pressure of about 3 kPa to about 10 kPa. ２ Next, the temperature is increased at a rate of 5°C / min under reduced pressure and in a He flow, and the CO desorbed at each temperature is measured. ２ The concentration of CO in the resulting TPD desorption curve is measured using a quadrupole mass spectrometer. ２ The amount of CO desorption was calculated from the area of ​​the peaks with a peak temperature of less than 200°C. ２ The amount of desorption was measured using low-temperature CO ２ As the quadrupole mass spectrometer, an "OmniStar GSD301" model manufactured by Pfeiffer Vacuum GmbH (used in the examples described below) or an equivalent product can be used.

[0016] In some embodiments of the presently disclosed technology, the mesoporous alumina has a low-temperature CO 2 content measured under reduced pressure by the method described above. ２ The desorption amount (hereinafter referred to as "low-pressure low-temperature CO ２ Alternatively, the desorption amount of CO ２ In addition to the amount of desorption, CO measured by the following method ２ Desorption amount (hereinafter referred to as "low-temperature CO ２ The amount of CO desorption may be determined by using the CO desorption method under atmospheric pressure and low temperature. ２ Measurement method for desorption amount] The sample to be measured was heated to 500°C at a rate of 10°C / hr under atmospheric pressure of about 1 atm and held at that temperature for 60 minutes. Then, the sample was left to stand and CO was added to a sample tube maintained at 35°C. ２ CO gas is passed through the sample. ２ After that, excess CO was removed by using He gas under atmospheric pressure of about 1 atm. ２ Next, under atmospheric pressure of about 1 atm, the temperature was raised to 500°C at a rate of 10°C / hr in a He flow, and CO desorbed at each temperature was measured. ２ The concentration of CO in the resulting TPD desorption curve is measured using a quadrupole mass spectrometer. ２ The amount of CO desorption was calculated from the area of ​​the peaks with a peak temperature of less than 200°C. ２ The amount of desorption was measured using this sample under atmospheric pressure and low temperature CO ２ As the quadrupole mass spectrometer, an MKS Cirrus 2 (used in the examples described later) manufactured by MKS Instruments UK Ltd. or an equivalent product can be used.

[0017] Mesoporous alumina at atmospheric pressure and low temperature CO ２ The desorption amount may be, for example, 5 μmol / g or more, 10 μmol / g or more, 20 μmol / g or more, or 30 μmol / g or more. ２The increased desorption amount tends to increase the amount of the adsorbed element (e.g., Mo) retained per unit weight of mesoporous alumina. From this perspective, in some embodiments, the mesoporous alumina is subjected to low-temperature CO sorption under atmospheric pressure. ２ The desorption amount is suitably 35 μmol / g or more, advantageously 45 μmol / g or more, preferably 55 μmol / g or more, and may 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. ２ The upper limit of the desorption amount is not particularly limited, and may be any amount that is theoretically possible in relation to the specific surface area of ​​the mesoporous alumina. ２ The desorption amount may be, for example, 400 μmol / g or less, 300 μmol / g or less, 250 μmol / g or less, 230 μmol / g or less, or 200 μmol / g or less.

[0018] The mesoporous alumina is at least ３ In an embodiment satisfying the desorption amount, the low-temperature NH ３ The desorption amount can be 25 μmol / g or more. ３ Mesoporous alumina that satisfies the desorption amount is more effective at lower temperatures than NH ３ The amount of the adsorbed element retained per unit weight tends to be larger than that of mesoporous alumina, which has a smaller desorption amount. ３ The desorption amount is preferably 30 mol / g or more, and may be 40 μmol / g or more, 50 μmol / g or more, 60 μmol / g or more, or 70 μmol / g or more. ３ There is no particular upper limit to the amount of desorption, and it may be any amount that is theoretically possible in relation to the specific surface area of ​​mesoporous alumina. ３The desorption amount may be, for example, 700 μmol / g or less, 500 μmol / g or less, or 400 μmol / g or less. In some embodiments, from the viewpoints of ease of production, handling, storage, quality stability, etc., low-temperature NH ３ The desorption amount may be, for example, 300 μmol / g or less, less than 200 μmol / g, 150 μmol / g or less, 100 μmol / g or less, 80 μmol / g or less, or 60 μmol / g or less.

[0019] Here, low-temperature NH ３ The amount of desorption is NH ３ Thermal desorption analysis (NH ３ -TPD), and specifically, it is measured by the following method. The same method is also used in the examples described later. ３ Measurement method for the amount of desorption] A sample to be measured is left at 150°C under reduced pressure of 1 Pa or less for 10 hours, and then the sample is left to stand and NH ３ The sample was then treated with NH ３ After that, the gas was switched to He, and excess NH was removed under a reduced pressure of about 3 kPa to about 10 kPa. ３ Next, the temperature is increased at a rate of 10°C / min under reduced pressure and He flow, and the NH desorbed at each temperature is measured. ３ The concentration of NH in the peak is measured based on the area of ​​each peak. ３ The amount of NH desorption was calculated from the area of ​​the peak with a peak temperature of less than 300°C. ３ The amount of desorption was measured using low-temperature NH ３ As the quadrupole mass spectrometer, an "OmniStar GSD301" model manufactured by Pfeiffer Vacuum GmbH (used in the examples described below) or an equivalent product can be used.

[0020] In the technology disclosed herein, the specific surface area of ​​the mesoporous alumina is not particularly limited. The specific surface area is, for example, about 50 m ２In some embodiments, from the viewpoint of increasing the contact area with the element to be adsorbed, the specific surface area is about 100 m ２ / g or more, and is approximately 130m ２ / g or more, and is preferably about 150m ２ / g or more, and is preferably about 190m ２ / g or more, and is approximately 220m ２ In view of the strength and durability of the mesoporous alumina, in some embodiments, the specific surface area is, for example, about 500 m ２ / g or less, and ２ / g or less, and is approximately 300m ２ / g or less, and is approximately 270m ２ / g or less, and is approximately 220m ２ The specific surface area can be measured by a nitrogen gas adsorption measurement method (BET method). The same method is also used in the examples described later.

[0021] In the technology disclosed herein, the average pore diameter of the mesoporous alumina is not particularly limited, but is typically within the range of approximately 2 nm to approximately 50 nm. In some embodiments, from the viewpoint of easily achieving the specific surface area described above, the average pore diameter is suitably approximately 40 nm or less, preferably approximately 30 nm or less, more preferably approximately 25 nm or less, and may be less than approximately 20 nm, less than approximately 15 nm, less than approximately 13 nm, less than approximately 11 nm, or less than approximately 9 nm. Furthermore, in some embodiments, from the viewpoint of contact efficiency with the adsorption target element, the average pore diameter is suitably approximately 4 nm or more, preferably approximately 6.5 nm or more, may be approximately 8 nm or more, approximately 10 nm or more, approximately 13 nm or more, or approximately 16 nm or more. The average pore diameter can be measured by a nitrogen gas adsorption measurement method (BJH method). A similar method is also used in the examples described below.

[0022] In the technology disclosed herein, the pore volume of the mesoporous alumina is not particularly limited. In some embodiments, the pore volume is set to approximately 0.2 cm3 from the viewpoint of contact efficiency with the element to be adsorbed. ３ / g or more, and ３ / g or more, and is preferably about 0.5 cm ３ / g or more, and is preferably about 0.7 cm ３ / g or more, and is approximately 1.1 cm ３ In addition, from the viewpoint of the strength and durability of the mesoporous alumina, in some embodiments, the pore volume may be, for example, about 3.0 cm ３ / g or less, and is approximately 2.2 cm ３ / g or less, and is approximately 1.7 cm ３ / g or less, and is approximately 1.2 cm ３ / g or less, and is approximately 0.8 cm ３ The pore volume can be measured by a nitrogen gas adsorption measurement method. The same method is also used in the examples described later.

[0023] The mesoporous alumina in the technology disclosed herein is preferably calcined to produce γ-alumina (also called activated alumina), since this tends to increase the amount of the target element retained per weight. Whether the mesoporous alumina is γ-alumina can be confirmed, for example, by X-ray diffraction.

[0024] The method for producing mesoporous alumina in the technology disclosed herein is not particularly limited. Those skilled in the art can obtain mesoporous alumina having a predetermined surface hydroxyl group content and a predetermined amount of mesoporous alumina by appropriately selecting a production method, selecting materials to be used, and setting production and treatment conditions based on one or more known techniques. ２ Desorption amount (or a predetermined amount of CO at low temperature under normal pressure) ２ Desorption amount) and a predetermined low-temperature NH ３ Mesoporous alumina can be manufactured to satisfy one, two, or three of the desorption amounts, providing the mesoporous alumina for use in any of the adsorption methods disclosed herein.

[0025] Examples of the known techniques include, but are not limited to, calcining an alumina precursor obtained by drying a slurry prepared by mixing an aluminum source, a pore-forming agent, and an aqueous solvent; calcining an alumina sol or alumina hydrate; removing a surfactant from an alumina precursor obtained by a sol-gel method using surfactant micelles as a pore-forming template by techniques such as calcination or washing; and production using an evaporation-induced self-assembly method. The calcination is preferably carried out so as to produce 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) can be preferably employed.

[0026] The aluminum source may be an organoaluminum compound or its hydrolyzate. Examples of the organoaluminum compound include aluminum alkoxides such as aluminum isopropoxide. Examples of the pore-forming agent or template include, but are not limited to, inorganic compounds that decompose to generate gas upon heating at or below the calcination temperature (preferably compounds belonging to at least one of ammonium salts, carbonates, and bicarbonates, such as ammonium carbonate, ammonium bicarbonate, and sodium bicarbonate), and organic compounds that can be decomposed and removed by heating (e.g., polymers such as glucose, and polymer nanospheres such as polydiaminopyridine nanospheres). The amount of the pore-forming agent (e.g., the inorganic compound) used per 100 parts by weight of the aluminum source (e.g., aluminum alkoxide) may be, for example, 50 parts by weight or more, preferably 100 parts by weight or more.

[0027] The adsorption method disclosed herein is a method for adsorbing CO 2 at a predetermined amount of surface hydroxyl groups as described above under a predetermined reduced pressure and low temperature. ２ Desorption amount (or a predetermined amount of CO at low temperature under normal pressure) ２ Desorption amount) and a predetermined low-temperature NH ３The method includes preparing mesoporous alumina that satisfies one, two, or three of the desorption amounts, and contacting the mesoporous alumina with a liquid containing an element to be adsorbed. The adsorption method can be preferably carried out using the mesoporous alumina disclosed herein. By contacting mesoporous alumina with a liquid containing an element to be adsorbed, the element to be adsorbed contained in the liquid containing the element to be adsorbed can be adsorbed onto the mesoporous alumina. Here, adsorbing the element to be adsorbed onto the mesoporous alumina can also be understood as removing or separating the element to be adsorbed using the mesoporous alumina. Therefore, the subject matter disclosed in this specification encompasses techniques for adsorbing, separating, or removing an element to be adsorbed using mesoporous alumina.

[0028] The element to be adsorbed 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. In some embodiments, the element to be adsorbed 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. In some embodiments, the element to be adsorbed 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 method disclosed herein include, but are not limited to, Ti, Cr, Co, Ni, Cu, Zn, Zr, Mo, and Pb.

[0029] The content of the element to be adsorbed in the liquid containing the element to be adsorbed is not particularly limited. In some embodiments, the content of the element to be adsorbed can be, for example, greater than 0 g / L and less than 20 g / L. The mesoporous alumina disclosed herein can also be preferably used to adsorb the element to be adsorbed from a liquid containing the element to be adsorbed, for example, in a liquid containing the element to be adsorbed of 20,000 ppm or less, 10,000 ppm or less, or 5,000 ppm or less. The content of the element to be adsorbed can be, for example, 1 ppm or more, 10 ppm or more, or 100 ppm or more.

[0030] Although not particularly limited, the pH of the liquid containing the element to be adsorbed may be, for example, approximately 2 to 12, 2 to 10, or 2 to 8. The technology disclosed herein is preferably applicable to a liquid containing an element to be adsorbed having a pH of, for example, 2 to 6. From the viewpoint of the durability of mesoporous alumina, it is advantageous for the pH of the liquid containing the element to be adsorbed to be approximately 2.5 or higher. In some embodiments, the pH may be 3 or higher, 4 or higher, or 4.5 or higher. In other embodiments, the pH may be 5.5 or lower, 4 or lower, or 3 or lower. To adjust the pH of the liquid containing the element to be adsorbed, an appropriate amount of pH adjuster can be used as needed. Examples of pH adjusters that can be used include, but are not limited to, potassium hydroxide, sodium hydroxide, hydrochloric acid, nitric acid, sulfuric acid, and the like. The pH adjusters can be used alone or in appropriate combinations of two or more.

[0031] The temperature of the liquid containing the element to be adsorbed that is brought into contact with the mesoporous alumina is not particularly limited and may be, for example, about 0° C. to 60° C. In some preferred embodiments, the temperature of the liquid containing the element to be adsorbed may be 10° C. or higher, 20° C. or higher, or 50° C. or lower, or 40° C. or lower. From the standpoint of ease of operation, a preferred embodiment is to bring the liquid into contact at room temperature (typically 20° C. to 30° C.).

[0032] The manner in which the mesoporous alumina is brought into contact with the liquid containing the element to be adsorbed is not particularly limited, and the contact can be carried out, for example, by passing the liquid through or immersing the mesoporous alumina in a single pass, or by circulating the liquid containing the element to be adsorbed.

[0033] Any mesoporous alumina disclosed herein can be preferably used for various applications in various fields, in addition to applications for adsorption of target elements. Examples of applications of any mesoporous alumina disclosed herein include, but are not limited to, metal ion adsorbents, metal ion separators, liquid adsorbents, liquid filters, liquid separators, gas adsorbents, gas filters, gas separators, water absorbents, water retention materials, humidity conditioners, wastewater treatment materials, aroma and deodorizing carriers, food purification and sterilization materials, separation and concentration materials for pharmaceutical and other bacterial cells, drug delivery carriers, cosmetic materials, catalyst carriers, bioreactor and microorganism support materials, humidity sensor materials, sound absorption and sound deadening materials, thermal insulation materials, and heat shielding materials. The matters disclosed in this specification may include the use of mesoporous alumina in any of the above applications and mesoporous alumina used in such applications.

[0034] The matters disclosed in this specification include the following: [1] A method for adsorbing elements belonging to Periods 4 to 6 and Groups 3 to 15 of the periodic table, comprising the following (1) to (3): (1) the amount of surface hydroxyl groups measured by the following method is 3.5 mmol / g or more; (2) the amount of surface hydroxyl groups measured by the following method is 3.5 mmol / g or more; ２ (3) The amount of desorption is 5 μmol / g or more; and (4) The amount of desorption is 5 μmol / g or more; and (5) The amount of desorption is 5 μmol / g or more; and (6) The amount of desorption is 5 μmol / g or more; and ３an amount of physisorbed water is 25 μmol / g or more; and a liquid containing an element to be adsorbed is brought into contact with the mesoporous alumina to adsorb the element to be adsorbed onto the mesoporous alumina, wherein the element to be adsorbed is at least one element selected from the group consisting of elements belonging to Periods 4 to 6 and Groups 3 to 15 of the periodic table. [Method for measuring the amount of surface hydroxyl groups] A container containing a sample to be measured and water is placed in a desiccator, and water vapor is adsorbed onto the hydroxyl groups present on the sample surface. After a sufficient time (preferably 3 hours or more) has passed, the sample is heated from room temperature to 200°C at a rate of 5°C / min using a thermogravimetric-differential calorimeter, and then held for 12 hours, and the weight loss due to desorption of physically adsorbed water from the sample is measured. The sample is then heated to 900°C at a rate of 5°C / min and held at this temperature for 12 hours to measure the amount of water removed by dehydration condensation of two adjacent hydroxyl groups. From the results obtained, the amount of surface hydroxyl groups [mmol / g] is calculated using the following formula: Amount of surface hydroxyl groups [mmol / g] = 1.111 × ΔW2 / (1-ΔW1 / 100) [low-temperature CO ２ Measurement method for the amount of desorption] A sample to be measured is left under reduced pressure (1 Pa or less) at 150°C for 10 hours, and then the sample is left to stand and CO is added to a sample tube maintained at 40°C. ２ CO gas is passed through the sample. ２ After that, excess CO was removed by using He gas under a reduced pressure of about 3 kPa to about 10 kPa. ２ Next, the temperature is increased at a rate of 5°C / min under reduced pressure and in a He flow, and the CO desorbed at each temperature is measured. ２ The concentration of CO in the resulting TPD desorption curve is measured using a quadrupole mass spectrometer. ２ The amount of CO desorption was calculated from the area of ​​the peaks with a peak temperature of less than 200°C. ２ The amount of desorption was measured by subjecting this sample to low-temperature CO ２ The amount of desorption is expressed as the low-temperature NH ３Measurement method for the amount of desorption] A sample to be measured is left at 150°C under reduced pressure of 1 Pa or less for 10 hours, and then the sample is left to stand and NH ３ The sample was then treated with NH ３ After that, the gas was switched to He, and excess NH was removed under a reduced pressure of about 3 kPa to about 10 kPa. ３ Next, the temperature is increased at a rate of 10°C / min under reduced pressure and He flow, and the NH desorbed at each temperature is measured. ３ The concentration of NH in the peak is measured based on the area of ​​each peak. ３ The amount of NH desorption was calculated from the area of ​​the peak with a peak temperature of less than 300°C. ３ The amount of desorption was measured using low-temperature NH ３ This is the amount of desorption.

[0035] [2] The method according to [1] above, wherein the mesoporous alumina satisfies at least the above (2).

[0036] [3] The mesoporous alumina comprises at least the above (2) and the following (4): (4) low-temperature CO 2 at atmospheric pressure measured by the following method ２ The method according to the above item [1], wherein mesoporous alumina satisfying the above condition is prepared. ２ Measurement method for desorption amount] The sample to be measured was heated to 500°C at a rate of 10°C / hr under atmospheric pressure of about 1 atm and held at that temperature for 60 minutes. Then, the sample was left to stand and CO was added to a sample tube maintained at 35°C. ２ CO gas is passed through the sample. ２ After that, excess CO was removed by using He gas under atmospheric pressure of about 1 atm. ２ Next, under atmospheric pressure of about 1 atm, the temperature was raised to 500°C at a rate of 10°C / hr in a He flow, and CO desorbed at each temperature was measured. ２The concentration of CO in the resulting TPD desorption curve is measured using a quadrupole mass spectrometer. ２ The amount of CO desorption was calculated from the area of ​​the peaks with a peak temperature of less than 200°C. ２ The amount of desorption was measured using this sample under atmospheric pressure and low temperature CO ２ This is the amount of desorption.

[0037] [4] A method for adsorbing elements belonging to Periods 4 to 6 and Groups 3 to 15 of the periodic table, comprising the following (1), (3), and (4): (1) the amount of surface hydroxyl groups measured by the method described in [1] above is 3.5 mmol / g or more; (3) the amount of low-temperature NH ３ (4) The amount of CO desorbed is 25 μmol / g or more; and (5) the amount of CO desorbed is 25 μmol / g or more; and (6) the amount of CO desorbed is 25 μmol / g or more; and ２ and the desorption amount is 5 μmol / g or more (e.g., 35 μmol / g or more); and bringing the mesoporous alumina into contact with a liquid containing an element to be adsorbed, thereby adsorbing the element to be adsorbed onto the mesoporous alumina, wherein the element to be adsorbed is at least one element selected from the group consisting of elements belonging to Periods 4 to 6 and Groups 3 to 15 of the periodic table. ２ Measurement method for desorption amount] The sample to be measured was heated to 500°C at a rate of 10°C / hr under atmospheric pressure of about 1 atm and held at that temperature for 60 minutes. Then, the sample was left to stand and CO was added to a sample tube maintained at 35°C. ２ CO gas is passed through the sample. ２ After that, excess CO was removed by using He gas under atmospheric pressure of about 1 atm. ２ Next, under atmospheric pressure of about 1 atm, the temperature was raised to 500°C at a rate of 10°C / hr in a He flow, and CO desorbed at each temperature was measured. ２ The concentration of CO in the resulting TPD desorption curve is measured using a quadrupole mass spectrometer. ２ The amount of CO desorption was calculated from the area of ​​the peaks with a peak temperature of less than 200°C.２ The amount of desorption was measured using this sample under atmospheric pressure and low temperature CO ２ This is the amount of desorption.

[0038] [5] The method according to [4] above, wherein mesoporous alumina satisfying at least (4) above is prepared as the mesoporous alumina.

[0039] [6] The mesoporous alumina is 100 m ２ The method according to any one of [1] to [5] above, wherein the specific surface area is 1 / g or more.

[0040] [7] The method according to any one of [1] to [6] above, wherein the mesoporous alumina has an average pore diameter of 2 nm or more and 30 nm or less.

[0041] [8] The method according to any one of [1] to [7] above, wherein the liquid containing the element to be adsorbed has a pH of 2 to 6.

[0042] [9] Mesoporous alumina used in the method according to any one of [1] to [8] above.

[0043]

[10] A mesoporous alumina used for adsorption of elements belonging to Periods 4 to 6 and Groups 3 to 15 of the periodic table, comprising the following (1) to (3): (1) a surface hydroxyl group amount measured by the method described in [1] above of 3.5 mmol / g or more; (2) a surface hydroxyl group amount measured by the method described in [1] above of 3.5 mmol / g or more; ２ (3) The amount of desorption is 5 μmol / g or more; and (4) the amount of desorption of NH at low temperature measured by the method described in [1] above. ３ The amount of desorption is 25 μmol / g or more.

[0044]

[11] The mesoporous alumina according to

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

[0045]

[12] At least the above (2) and the following (4): (4) Low-temperature CO under normal pressure measured by the method described in [4] above ２ The mesoporous alumina according to

[11] above, which satisfies the above condition: the desorption amount is 5 μmol / g or more (for example, 35 μmol / g or more).

[0046]

[13] A mesoporous alumina used for adsorption of elements belonging to Periods 4 to 6 and Groups 3 to 15 of the periodic table, comprising the following (1), (3), and (4): (1) a surface hydroxyl group amount measured by the method described in [1] above of 3.5 mmol / g or more; (3) a low-temperature NH ３ (4) The amount of CO desorbed is 25 μmol / g or more; and (5) the amount of CO desorbed at low temperature under normal pressure measured by the method described in [4] above. ２ The desorption amount is 5 μmol / g or more (for example, 35 μmol / g or more).

[0047]

[14] The mesoporous alumina according to

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

[0048]

[15] The mesoporous alumina is 100 m ２ The mesoporous alumina according to any one of

[10] to

[14] above, having a specific surface area of ​​1 / g or more.

[0049]

[16] The mesoporous alumina according to any one of

[10] to

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

[0050] Hereinafter, several examples of the present invention will be described, but it is not intended that the present invention be limited to the specific examples shown.

[0051] <<Experimental Example 1>> <Preparation of Mesoporous Alumina> (Preparation Example 1) 970 g of distilled water was placed in a container at room temperature, and 60 g of ammonium carbonate was added and dissolved while stirring. Then, 32 g of powdered aluminum isopropoxide was added, and stirring was continued at room temperature for 24 hours to prepare an intermediate liquid. This intermediate liquid was transferred to a heat-resistant container and dried at 80°C for 48 hours to obtain an alumina precursor powder. This was calcined at 700°C for 5 hours in a calcination furnace in an air atmosphere, and then crushed and passed through a 50-mesh wire screen. In this way, mesoporous alumina (specific surface area 219 m) of Sample 1 was obtained. ２ / g, pore volume 1.63 cm ３ / g, average pore diameter 11.1 nm) was prepared.

[0052] (Preparation Example 2) Mesoporous alumina of Sample 2 (specific surface area: 224 m) was prepared in the same manner as in the preparation of mesoporous alumina of Sample 1, except that the amount of ammonium carbonate used was changed to 30 g. ２ / g, pore volume 0.61 cm ３ / g, average pore diameter 9.6 nm) was prepared.

[0053] (Preparation Example 3) Commercially available alumina sol (Nissan Chemical Industries, Ltd., AS-200) was calcined in a calcination furnace under an atmospheric atmosphere at 700°C for 5 hours, then crushed and passed through a 50-mesh wire mesh. In this way, mesoporous alumina (specific surface area: 204 m) of Sample 3 was obtained. ２ / g, pore volume 0.49 cm ３ / g, average pore diameter 8.3 nm) was prepared.

[0054] Sample 4 was a commercially available mesoporous alumina (Sigma Aldrich, product number 199966, Brockmann activity I, specific surface area 154 m ２ / g, pore volume 0.25 cm ３ / g, average pore diameter 6 nm) was used.

[0055] <Amount of surface hydroxyl groups, low-temperature CO under reduced pressure ２ Desorption amount, low temperature NH ３ Measurement of the amount of hydroxyl groups on the surface of Samples 1 to 4 (S ＯＨ ), low-temperature CO under reduced pressure ２ Desorption amount (L ＣＯ２ ) and low-temperature NH ３ Desorption amount (L ＮＨ３ ) were measured by the methods described above. The results are shown in Table 1.

[0056] <Adsorption Test (Implementation of Adsorption Method)> Mesoporous alumina samples 1 to 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 as the target element for adsorption was passed through the column at a rate of 5 mL / min using a pump. The Mo concentrations of the liquid before and after passing through the column were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). The Mo retention amount [mg / g] was calculated by converting the amount of Mo lost after passing through the column relative to the amount before passing into a value per gram of sample. The liquid passed through the column was a 0.25 wt% aqueous solution of sodium molybdate, the pH of which was adjusted to 2.5 with nitric acid (Mo concentration: 900 ppm). The results are shown in Table 1.

[0057]

[0058] The sample obtained above was subjected to low-temperature CO 2 ２ The desorption amount was measured and found to be 167.0 μmol / g for Sample 1 and 146.6 μmol / g for Sample 3. ２ The amount of desorption was significantly smaller than that of Samples 1 and 3. As can be seen from these measurement results and the amount of Mo retained in each sample shown in Table 1, ２ In the above-mentioned adsorption test, even when the pH of the liquid passed through the column was changed to 2.0, the adsorption was performed under normal pressure and low temperature CO ２ A similar correlation was observed between the amount of desorption and the amount of Mo retained.

[0059] <<Experimental Example 2>> Similar adsorption tests were performed on Samples 1, 3, and 4 used in the adsorption test in Experimental Example 1, using Zr, Co, Cr, Cu, Ni, and Zu as the adsorption target elements, to determine the retention amount of each metal element. As the liquid containing the adsorption target elements to be passed through the column, an ICP standard solution (Merck) containing each element at a concentration of approximately 1000 ppm was used, with the pH adjusted to 2.5 or 5 using KOH. The results are shown in Table 2. Note that N / A in Table 2 indicates that the test was not performed.

[0060]

[0061] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

Claims

1. A method for adsorbing an element belonging to the 4th to 6th periods and the 3rd to 15th groups of the periodic table, comprising the following (1) to (3): (1) the amount of surface hydroxyl groups is 3.5 mmol / g or more; (2) CO ２ In a temperature programmed desorption analysis using as a probe molecule, CO desorbed at a peak temperature of less than 200° C. ２ (3) NH ３ In a thermal desorption analysis using as a probe molecule, NH desorbed at a peak temperature of less than 300° C. ３ and (b) contacting the mesoporous alumina with a liquid containing an element to be adsorbed to cause the element to be adsorbed to be adsorbed onto the mesoporous alumina, wherein the element to be adsorbed is at least one element selected from the group consisting of elements belonging to Periods 4 to 6 and Groups 3 to 15 of the periodic table.

2. The mesoporous alumina is 100 mm ２ The method according to claim 1, wherein the specific surface area is 0.05 to 1.0 g / g or more.

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

4. A method according to any one of claims 1 to 3, wherein the liquid containing the element to be adsorbed has a pH of 2 to 6.

5. Mesoporous alumina for use in the method according to any one of claims 1 to 4.

6. Mesoporous alumina used for adsorption of elements belonging to the 4th to 6th periods and the 3rd to 15th groups of the periodic table, comprising the following (1) to (3): (1) the amount of surface hydroxyl groups is 3.5 mmol / g or more; (2) CO ２ In a temperature programmed desorption analysis using as a probe molecule, CO desorbed at a peak temperature of less than 200° C. ２ (3) NH ３ In a thermal desorption analysis using as a probe molecule, NH desorbed at a peak temperature of less than 300° C. ３ The amount of the mesoporous alumina is 25 μmol / g or more.