Adsorbent, and method for producing adsorbent

Abstract

Provided is a novel absorbent for a perfluoroalkyl compound and a polyfluoroalkyl compound, wherein the absorbent does not contain much carbon material such as activated carbon. The absorbent for a perfluoroalkyl compound and a polyfluoroalkyl compound comprises a porous body containing magnesium oxide and aluminum oxide. The content of magnesium oxide exceeds 9 mass%.

Description

Adsorbent and method for producing the same

[0001] The present invention relates to an adsorbent and a method for producing the adsorbent.

[0002] In recent years, environmental pollution caused by organic fluorine compounds (PFAS) (per- and polyfluoroalkyl substances: perfluoroalkyl compounds, polyfluoroalkyl compounds, their salts, and their derivatives) has become a problem. Among PFAS, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are particularly toxic. These organic fluorine compounds are known as persistent organic pollutants.

[0003] It is known that inexpensive activated carbon is used to remove persistent organic pollutants from contaminated water. Patent Document 1 below discloses an adsorbent having a carbon material such as activated carbon containing calcium or magnesium.

[0004] Special Publication No. 2022-526606

[0005] However, the adsorbents described in the prior art documents are mainly made of activated carbon, and such adsorbents containing activated carbon must be incinerated at high temperatures for disposal after adsorption of PFAS, which can generate large amounts of carbon dioxide during disposal.

[0006] Therefore, there is a need for adsorbents for perfluoroalkyl and polyfluoroalkyl compounds that have novel compositions that are less likely to contain activated carbon or carbonaceous materials that generate carbon dioxide.

[0007] An adsorbent for perfluoroalkyl and polyfluoroalkyl compounds according to one embodiment comprises a porous body containing magnesium oxide and aluminum oxide, wherein the magnesium oxide content is greater than 9% by mass.

[0008] A method for producing an adsorbent for perfluoroalkyl compounds and polyfluoroalkyl compounds according to one embodiment includes the steps of mixing a magnesium oxide precursor, an aluminum oxide precursor, and water, granulating the mixture, and firing the granules.

[0009] It should be noted that the present disclosure is not limited to the particular devices and methods described. The terminology used in this disclosure is for the purpose of describing particular embodiments or examples and is not intended to limit the scope of the claims.

[0010] The adsorbent according to one embodiment is for adsorbing organic fluorine compounds, preferably PFAS (perfluoroalkyl compounds, polyfluoroalkyl compounds, salts thereof, and derivatives thereof). In this specification, the adsorbent for adsorbing PFAS is referred to as a PFAS adsorbent. However, hereinafter, for simplicity, the PFAS adsorbent may also be simply referred to as an "adsorbent."

[0011] Examples of PFAS include perfluoroalkyl sulfonates, perfluoroalkanesulfonic acid (PFSA), N-butylperfluoroalkanesulfonamide (BuFASA), N-butylperfluoroalkanesulfonamidoethanol (BuFASE), N-butylperfluoroalkanesulfonamidoacetic acid (BuFASAA), N-ethylperfluoroalkanesulfonamide (EtFASA), N-ethylperfluoroalkanesulfonamidoethanol (EtFASE), N-ethylperfluoroalkanesulfonamidoacetic acid (EtFASAA), perfluoroalkanesulfonamide (FASA), perfluoroalkanesulfonamidoethanol (FASE), perfluoroalkanesulfonamidoacetic acid (FASAA), N-methylperfluoroalkane perfluoroalkanesulfonamidoacetic acid (MeFASA), N-methylperfluoroalkanesulfonamidoethanol (MeFASE), N-methylperfluorooctanesulfonamide (MeFOSA), perfluoroalkanesulfonyl fluoride (PASF), 4,8-dioxa-3H-perfluorononanoic acid, ammonium perfluorooctanoate (APFO), fluoroprotein (FP), fluorotelomer carboxylic acid (FTCA), fluorotelomer alcohol (FTOH), fluorotelomer sulfonate (FTS), fluorotelomer sulfonic acid (FTSA), perfluoroalkyl acid (PFAA), perfluoroalkylsulfonamidoethanol (PFOSE), and any derivatives thereof. This includes, for example, perfluorooctanoic acid (PFOA), perfluorooctanesulfonate, perfluorooctanesulfonic acid (PFOS), 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)propanoate, ammonium 2,3,3,3-tetrafluoroethyl-2-(heptafluoropropoxy)propanoate, 1,2,2,2-Tetrafluoroethyl ether, 4:2-fluorotelomer sulfonic acid (4:2 FtS), 6:2-fluorotelomer sulfonic acid (6:2 FtS), 8:2-fluorotelomer sulfonic acid (8:2 FtS), perfluorobutanoic acid (PFBA), perfluorobutane sulfonate, perfluorobutane sulfonic acid (PFBS), perfluorohexane sulfonate, perfluorohexane sulfonic acid (PFHxS), perfluorohexanoate, perfluorohexanoic acid (PFHxA), 4,8-Dioxa-3H-perfluorononanoic acid, ammonium perfluorooctanoate (APFO), N-ethylperfluorooctanesulfonamide (EtFOSA), N-ethylperfluorooctanesulfonamidoethanol (EtFOSE), perfluorooctanesulfonamide (PFOSA), perfluorooctanesulfonamidoacetic acid (FOSAA), perfluorooctanesulfonamidoethanol (FOSE), perfluorobutanoate, perfluorobutanoic acid, Perfluorobutyrate, Perfluorobutyric Acid, Perfluoroalkyl Carboxylate, Perfluoroalkyl Carboxylate (PFCA), Perfluorodecanoate, Perfluorodecanoic Acid (PFDA), Perfluorododecanoate, Perfluorododecanoic Acid (PFDoA), Perfluorododecanesulfonate (PFDoS), Perfluorododecanesulfonic Acid (PFDoSA), Perfluorodecanesulfonate, Perfluorodecanesulfonic Acid (PFDS), Perfluorohept Perfluorooctanoic acid, perfluoroheptanoic acid (PFHpA), perfluoroheptanesulfonate, perfluoroheptanesulfonic acid (PFHpS), perfluorononanoic acid, perfluorononanoic acid (PFNA), perfluorononanesulfonate, perfluorononanesulfonic acid (PFNS), perfluorooctanoic acid, perfluorophosphonic acid (PFPA), perfluoropentanoic acid, perfluoropentanoic acid (PFPeA), perfluoropentanesulfonate, perfluoropenta Examples of suitable fluoroisopropyl ethers include perfluoroisopropyl ethersulfonic acid (PFPeS), perfluorophosphinic acid (PFpiA), perfluorotetradecanoic acid (PFTeDA), perfluorotridecanoic acid (PFTrDA), perfluoroundecanoate, perfluoroundecanoic acid (PFUnA), perfluoroundecanesulfonate (PFUnS), perfluoroundecanesulfonic acid (PFUnSA), polytetrafluoroethylene (PTFE), or 8:2 fluorotelomer alcohol (8:2 FTOH).

[0012] The perfluoroalkyl and polyfluoroalkyl compound adsorbents may be those that adsorb at least one of the PFAS listed above. The adsorbents may also be those that adsorb PFAS having a carbon number of 3 to 18, preferably 4 to 14, more preferably 6 to 10, and even more preferably 8. The adsorbents may be those that adsorb at least one of PFOA and PFOS, each of which has a carbon number of 8, for example.

[0013] The adsorbent has a porous body containing magnesium oxide, and the porous body preferably contains magnesium oxide and aluminum oxide, or is preferably made of magnesium oxide.

[0014] The content of magnesium oxide in the entire adsorbent may be 9% by mass or more, preferably more than 9% by mass, more preferably 15% by mass or more, and even more preferably 20% by mass or more, and may be 100% by mass or less.

[0015] The sum of the pore volume Vp(BJH) of the adsorbent (porous body) calculated by the BJH method and the pore volume Vp(MP) of the adsorbent (porous body) calculated by the MP method may be 0.40 mL / g or more and 2.00 mL / g or less. The sum of Vp(BJH) and Vp(MP) is preferably 0.50 mL / g or more and 1.40 mL / g or less, more preferably 0.60 mL / g or more and 1.00 mL / g or less, and even more preferably 0.68 mL / g or more and 0.84 mL / g or less.

[0016] In this specification, the pore volume Vp(BJH) of the adsorbent calculated by the BJH method and the pore volume Vp(MP) of the adsorbent (porous body) calculated by the MP method are calculated by analyzing nitrogen adsorption isotherms.

[0017] From the viewpoint of PFAS adsorption, with respect to the adsorbent (porous body), the ratio of Vp(BJH) to the sum of the pore volume Vp(BJH) calculated by the BJH method and the pore volume Vp(MP) calculated by the MP method may be 50% or more, preferably 55% or more, and more preferably 60% or more.

[0018] The lower limit of Vp(BJH) may be 0.20 mL / g or more, preferably 0.30 mL / g or more, and more preferably 0.40 mL / g or more. The upper limit of Vp(BJH) is not particularly limited, but may be 1.80 mL / g or less, 1.60 mL / g or less, 1.10 mL / g or less, or 0.60 mL / g or less. However, Vp(BJH) may be within a range that combines any of the above upper and lower limits.

[0019] The BET specific surface area of ​​the adsorbent is 50 m ２ / g or more, 100m ２ / g or more, or 150m ２ It is believed that the higher the BET specific surface area of ​​the adsorbent, the higher the PFAS adsorption capacity of the adsorbent.

[0020] The upper limit of the BET specific surface area of ​​the adsorbent is 800 m ２ / g or less, 500m ２ / g or less, 400m ２ / g or less, 375m ２ / g or less or 360m ２ / g or less.

[0021] The BET specific surface area can be measured by the BET multipoint method.

[0022] The pore volume (Vp(MP) and Vp(BJH)) and BET specific surface area can be changed by the magnesium oxide content, the hydration time or firing time described below, and the temperature during hydration or firing.

[0023] The adsorbent may contain aluminum oxide as described above. Preferably, the aluminum oxide may be formed by sintering hydraulic alumina that has been hydrated and hardened. By using such aluminum oxide, a porous body containing magnesium oxide and having the above-described pore volume and BET specific surface area can be easily produced.

[0024] The adsorbent may be in the form of a porous molded body (filter material). An adsorbent in the form of a porous molded body can maintain its shape in a solution, and therefore can be used as an easily recoverable filter material. The adsorbent may also be in the form of a porous powder.

[0025] When the adsorbent is in the form of a porous molded body (filter material), the adsorbent can be used while maintaining its shape without disintegrating in water. On the other hand, when the adsorbent is in the form of a powder, the adsorbent can be used by dispersing it in water. In addition, it is preferable that the porous body does not substantially contain carbon materials such as activated carbon. This can prevent the generation of large amounts of carbon dioxide due to incineration when the adsorbent is disposed of.

[0026] When the adsorbent has the form of a porous molded body, the shape of the porous molded body is not particularly limited. The shape of the porous molded body may be, for example, spherical, ellipsoidal, cylindrical, cylindrical, prismatic, honeycomb, etc. The size of the porous molded body, specifically the length of the longest part of the porous molded body (maximum length), is not particularly limited, but may be 0.5 mm or more, preferably 1 mm or more, more preferably 3 mm or more, and even more preferably 5 mm or more.

[0027] [Method for manufacturing an adsorbent] First, a step of forming granules by mixing at least a magnesium oxide precursor and water is carried out (granulation step). The magnesium oxide precursor may contain magnesium hydroxide, magnesium oxide, and at least one of basic magnesium carbonate, normal magnesium carbonate, anhydrous magnesium carbonate, and salts thereof. The aluminum oxide precursor may contain at least one of aluminum hydroxide, aluminum oxide, aluminum carbonate, and salts thereof.

[0028] When the adsorbent to be produced is composed of magnesium oxide alone and does not contain aluminum oxide, the granulation step is performed by mixing a magnesium oxide precursor with water and granulating the mixture. In this case, the purity of the magnesium oxide precursor may be 95% by mass or more.

[0029] When the adsorbent to be produced contains aluminum oxide, in the granulation step, the granules are formed by mixing a magnesium oxide precursor, an aluminum oxide precursor, and water and granulating the mixture.

[0030] Hydraulic alumina can be used as the aluminum oxide precursor. When hydraulic alumina is used, it hardens by hydration when mixed with water, making it easy to produce a porous body of a desired shape.

[0031] In the granulation step, the magnesium oxide precursor is mixed so that the magnesium oxide content after calcination (described later) is 9% by mass or more, preferably more than 9% by mass, more preferably 15% by mass, and even more preferably 20% by mass or more. The magnesium oxide content is the value excluding volatile components such as water contained in the granules.

[0032] When the adsorbent to be produced is made of magnesium oxide, the granules are formed by mixing only magnesium oxide precursor and water and granulating the mixture.

[0033] In the granulation step, it is desirable to mix water while adding it dropwise. The granulation method is not particularly limited, but extrusion granulation, rolling granulation, or any other granulation method can be used.

[0034] Preferably, the granules formed in the granulation step are exposed to steam to further hydrate and harden them (steaming step). The granules can be exposed to steam by being placed in a sealed container filled with water so as not to be submerged in water. In this case, the temperature inside the sealed container may be in the range of 25°C to 150°C. The time for which the granules are exposed to steam in the sealed container (hydration time) may be in the range of 0.5 to 36 hours.

[0035] In the above-mentioned granulation process, variations in the physical properties, hardness, etc. of the granules formed may occur depending on the temperature and humidity of the atmosphere. By carrying out the above-mentioned soaking process, such variations can be eliminated. After the soaking process, a drying process for drying the granules may be carried out.

[0036] Next, a step of calcining the granulated material (calcination step) is carried out. This forms a porous body (adsorbent) containing magnesium oxide and aluminum oxide, or a porous body consisting of magnesium oxide alone. The calcination temperature may be in the range of 300°C to 800°C. The calcination time may be in the range of 0.5 hours to 18 hours. Calcination can be carried out in an air atmosphere, a nitrogen atmosphere, or a vacuum using a calcination furnace.

[0037] The porous body made of magnesium oxide alone is produced in the form of a powder after the firing process. The porous body made of magnesium oxide alone may remain in the form of a powder, or may be formed into a filter material using any binder. On the other hand, the porous body containing magnesium oxide and aluminum oxide is produced in a state where the granulated form is maintained after the firing process. Therefore, the porous body containing magnesium oxide and aluminum oxide can be easily formed into a filter material having a specific shape.

[0038] The above-described adsorbent can be produced by the above steps, where the pore volume (Vp(MP) and Vp(BJH)) and BET specific surface area of ​​the porous body (adsorbent) can be adjusted by the magnesium oxide content, the hydration time or firing time, the hydration or firing temperature, the physical properties of the aluminum oxide precursor, etc.

[0039] [Examples] Examples will be described in detail below, but it should be noted that the present invention is not limited to the aspects described in the following examples.

[0040] Example 1: A mixture of 50 g of hydraulic alumina (BK-112 manufactured by Sumitomo Chemical) and 7.23 g of magnesium hydroxide (UD-650 manufactured by Ube Materials) was placed in an SUS container, and the container was set on a ball mill turntable. The ball mill was tilted at a certain angle and rotated at 300 rpm, while 24 g of water was added dropwise to form granules (granulation process). The granules were then placed in a sealed container, filled with water so that the granules did not come into contact with the water, and hydrated at 80°C for 16 hours to harden the granules (steaming process). The hardened granules were then dried at 100°C for 3 hours and then calcined in an electric furnace at 380°C for 3 hours to produce a porous body (adsorbent) (calcination process). The magnesium oxide content of the porous body was 9.1% by mass.

[0041] Example 2 A porous body (adsorbent) was produced in the same manner as in Example 1, except that the amount of magnesium hydroxide (UD-650 manufactured by Ube Material Industries, Ltd.) was changed to 21.69 g and the amount of water was changed to 28 g. The magnesium oxide content in the porous body was 23 mass%.

[0042] Example 3 A porous body (adsorbent) was produced in the same manner as in Example 1, except that the amount of hydraulic alumina (BK-112 manufactured by Sumitomo Chemical Co., Ltd.) was changed to 25 g, the amount of magnesium hydroxide to 36.15 g, and the amount of water to 22 g. The magnesium oxide content in the porous body was 50 mass%.

[0043] Example 4 50 g of magnesium hydroxide (UD-650, manufactured by Ube Material Industries, Ltd.) was placed in an SUS container, and the container was set on a turntable for a ball mill. While the ball mill was tilted at a certain angle and rotating at 300 rpm, 19 g of water was added dropwise and granulated to form a granulated product (granulation process). Next, the granulated product was placed in a sealed container, which was filled with water so that the granulated product would not come into contact with the water, and hydrated at 80°C for 16 hours (steaming process). The granulated product was fired in an electric furnace at 380°C for 3 hours to produce a porous body (adsorbent) (firing process). The porous body consisted of magnesium oxide alone.

[0044] Reference Example 1 Activated carbon (manufactured by UES, UCG-AG) was prepared as an adsorbent.

[0045] For the above Examples 1 to 4 and Reference Example 1, the BET specific surface area (S ＢＥＴ The results of measurements of Vp(MP), Vp(BJH), the sum of Vp(MP) and Vp(BJH), and the ratio of Vp(BJH) to the sum of Vp(MP) and Vp(BJH) are shown in Table 1 below. These measurements can be performed as follows.

[0046] Vp(MP) and Vp(BJH) were calculated by analyzing the nitrogen adsorption isotherm. Specifically, approximately 30 mg of an adsorbent sample was first weighed using a precision balance, and the sample was pretreated in a gas adsorption measurement device (BELSORP-miniX, manufactured by Microtrac-Bell) under a nitrogen atmosphere at 200°C for 10 minutes. The nitrogen adsorption isotherm was then measured using the gas adsorption measurement device. Here, the purity of the nitrogen gas was 99.999% or higher, the measurement temperature was 77K (liquid nitrogen temperature), and the measurement pressure was 0.0 to 101.3 kPa (relative pressure P / P0 = 0.0 to 1.0).

[0047] Vp(MP) was calculated from the obtained adsorption isotherm (BELMASTER ＴＭ 7) was calculated by the MP method using the integrated value of the pore size distribution of the sample.

[0048] Vp(BJH) was calculated from the obtained adsorption isotherm (BELMASTER ＴＭ 7) was calculated by the integrated value of the pore size distribution of the sample using the BJH method.

[0049] The BET specific surface area was measured by pre-treating the sample at 200° C. for 10 minutes and then measuring the BET multipoint method using a Tristar II 3020 (manufactured by Shimadzu Corporation) by nitrogen gas adsorption.

[0050] The sum of the pore volume Vp(BJH) calculated by the BJH method and the pore volume Vp(MP) of the adsorbent (porous body) calculated by the MP method for the adsorbents according to Examples 1 to 4 is 0.40 mL / g or more. In particular, the sum of Vp(BJH) and Vp(MP) for the adsorbents according to Examples 2 and 3 is greater than the sum of Vp(BJH) and Vp(MP) for the adsorbent according to Reference Example 1.

[0051] In addition, in Examples 1 to 4, the ratio of Vp(BJH) to the total value of Vp(MP) and Vp(BJH) (hereinafter simply referred to as the "Vp(BJH) ratio") is 50% or more. The Vp(BJH) ratios in Examples 1 to 4 are higher than the Vp(BJH) ratio in Reference Example 1.

[0052] [Table 1]

[0053] [Adsorption Experiment] Three types of aqueous solutions containing different concentrations of PFOS (potassium perfluorooctanesulfonate, Fujifilm Corporation, product code: 009151) were prepared. The initial PFOS concentrations in each solution were 300 mg / L, 25 μg / L, and 100 ng / L, respectively. The adsorbents of Examples 1 to 4 were added to the aqueous solutions so that the amount of each was 1000 mg / L, and the solutions were stirred at approximately 25°C for 1 hour using a mini rotator. In Examples 1 to 4 and Reference Example 1, all adsorbents were used after being powdered in a mortar. The adsorbents were then removed from the aqueous solutions using a syringe filter. The aqueous solutions from which the adsorbents had been removed were analyzed using a liquid chromatograph mass spectrometer (LC-MS / MS) to measure the PFOS concentration (X), and the removal rate was calculated using the formula (1 - (X / measured initial concentration)) x 100. The results of the PFOS removal rates are shown in Table 1 below. In Reference Example 1, activated carbon was added to an aqueous solution containing PFOS so that the amount of activated carbon was 1000 mg / L, and an adsorption experiment was carried out in the same manner as in Examples 1 to 4.

[0054] In an adsorption experiment using an aqueous solution containing a high concentration of PFOS (initial concentration: 300 mg / L), it is clear from Table 1 that the greater the magnesium oxide content in the adsorbent, the higher the adsorption capacity of the adsorbent. The adsorbent of Example 1 has a removal rate for high concentrations of PFOS close to that of the activated carbon of Reference Example 1. Therefore, an adsorbent with an MgO content of 9 mass % can be used to remove high concentrations of PFOS, similar to activated carbon.

[0055] The adsorbents of Examples 2 and 4 have a higher removal rate for high-concentration PFOS than the activated carbon of Reference Example 1. Therefore, adsorbents with an MgO content of more than 9 mass %, more preferably 15 mass % or more, are suitable for removing high-concentration PFOS.

[0056] In an adsorption experiment using an aqueous solution containing a medium concentration of PFOS (initial concentration: 25 μg / L), it is clear from Table 1 that the adsorbents of Examples 1 and 2 have a much higher adsorption capacity than the adsorbent of Reference Example 1. Therefore, an adsorbent made of a porous body containing magnesium oxide, more specifically a porous body containing magnesium oxide and aluminum oxide, can be suitably used to remove medium concentrations of PFOS.

[0057] Under normal circumstances, the concentration of PFOS in contaminated water is lower than 25 μg / L. Therefore, it is believed that the adsorbents in Examples 1 and 2 can exhibit a sufficient PFOS adsorption effect. Furthermore, since it is believed that the higher the magnesium oxide content, the greater the PFOS adsorption effect, it can be seen that porous bodies containing 9 mass % or more of magnesium oxide can be suitably used as PFOS adsorbents.

[0058] In an adsorption experiment using an aqueous solution containing a low concentration of PFOS (initial concentration: 100 ng / L), Table 1 shows that the adsorption capacity of the adsorbent increases as the magnesium oxide content in the adsorbent increases to a certain extent. Therefore, an adsorbent made of a porous material containing magnesium oxide can be suitably used to remove low concentrations of PFOS. An aqueous solution containing a low concentration of PFOS (initial concentration: 100 ng / L) can occur in a real environment. Therefore, an adsorbent made of a porous material containing magnesium oxide is considered to be practically usable as an adsorbent.

[0059] The adsorbents according to Examples 1 to 4 are considered to be applicable to the adsorption of PFAS, which is a compound of the same family as PFOS. Note that the adsorbents according to Examples 1 to 4 can also be used to adsorb substances other than PFAS.

[0060] The following provides supplementary explanations for the above-described embodiments and / or examples. As described above, the porous body serving as the adsorbent preferably does not substantially contain a carbon material such as activated carbon. In this case, the porous body may be substantially composed of magnesium oxide, or may be substantially composed of magnesium oxide and aluminum oxide.

[0061] Alternatively, the porous body may contain a small amount of carbon material such as activated carbon, in which case the proportion of carbon material in the porous body may be, for example, 10% by weight or less, preferably 5% by weight or less, and more preferably 3% by weight or less.

[0062] Therefore, when the main component of the porous body is magnesium oxide, the content of magnesium oxide in the porous body may be, for example, 90% by mass or more, preferably 95% by mass or more, and more preferably 97% by mass or more. When the main components of the porous body are magnesium oxide and aluminum oxide, the total content of magnesium oxide and aluminum oxide in the porous body may be, for example, 90% by mass or more, preferably 95% by mass or more, and more preferably 97% by mass or more.

[0063] From the above description of the embodiments and / or examples, it should be noted that at least the inventions described in the following appendices are clearly stated in this specification.

[0064] [Appendix 1] An adsorbent having a porous body containing magnesium oxide. [Appendix 2] The adsorbent according to Appendices 1, wherein the content of magnesium oxide in the porous body is 9% by mass or more, preferably more than 9% by mass, and more preferably 15% by mass or more. [Appendix 3] The adsorbent according to Appendices 1 or 2, wherein the sum of the pore volume Vp(BJH) calculated by the BJH method and the pore volume Vp(MP) calculated by the MP method is 0.40 mL / g or more and 2.00 mL / g or less. [Appendix 4] The adsorbent according to any one of Appendices 1 to 3, wherein the ratio of Vp(BJH) to the sum of the pore volume Vp(BJH) calculated by the BJH method and the pore volume Vp(MP) calculated by the MP method is 50% or more. [Appendix 5] The adsorbent according to any one of Appendices 3 to 4, wherein the porous body consists essentially of magnesium oxide. [Appendix 6] The adsorbent according to any one of Appendices 1 to 4, wherein the porous body comprises magnesium oxide and aluminum oxide. [Appendix 7] The adsorbent according to any one of Appendices 1 to 6, wherein the adsorbent is for adsorbing an organic fluorine compound, preferably PFAS. [Appendix 8] An adsorption method, comprising adsorbing an organic fluorine compound, preferably PFAS, using the adsorbent according to any one of Appendices 1 to 7. [Appendix 9] A method for producing an adsorbent, comprising a granulation step of mixing at least a magnesium oxide precursor and water and granulating to form a granule, and a firing step of firing the granule. [Appendix 10] The method for producing an adsorbent according to Appendices 9, wherein in the granulation step, the magnesium oxide precursor is mixed so that the magnesium oxide content after firing is 9% by mass or more, preferably more than 9% by mass, and more preferably 15% by mass or more. [Appendix 11] The method for producing an adsorbent according to Appendices 9 or 10, wherein the granules are formed by mixing a magnesium oxide precursor, an aluminum oxide precursor, and water and granulating the mixture. [Appendix 12] The method for producing an adsorbent according to Appendix 9 or 10, wherein the granules are formed by mixing substantially only magnesium oxide precursor and water, followed by granulation.[Appendix 13] The method for producing an adsorbent according to any one of Appendices 9 to 12, wherein the magnesium oxide precursor comprises at least one of magnesium hydroxide, magnesium oxide, and basic magnesium carbonate, normal magnesium carbonate, anhydrous magnesium carbonate, and salts thereof. [Appendix 14] The method for producing an adsorbent according to any one of Appendices 9 to 13, wherein the aluminum oxide precursor comprises at least one of aluminum hydroxide, aluminum oxide, aluminum carbonate, and salts thereof, preferably hydraulic alumina. [Appendix 15] The adsorbent according to any one of Appendices 1 to 7, wherein the porous body is substantially free of carbon materials. [Appendix 16] The adsorbent according to Appendices 6, wherein the total content of magnesium oxide and aluminum oxide in the porous body is 90% by mass or more. [Appendix 17] The adsorbent according to Appendices 6, wherein the porous body consists essentially of magnesium oxide and aluminum oxide. [Appendix 18] The adsorbent according to any one of Appendices 1 to 5, wherein the content of magnesium oxide in the porous body is 90% by mass or more. [Appendix 19] The adsorbent according to any one of Appendices 9 to 14, wherein the granules do not substantially contain a carbon material.

[0065] As described above, the contents of the present invention have been disclosed through embodiments and / or examples, but the descriptions that form part of this disclosure should not be understood as limiting the present invention. Various alternative embodiments, examples, and / or operating techniques will become apparent to those skilled in the art from this disclosure. Therefore, the technical scope of the present invention is defined only by the inventive features of the claims that can be reasonably understood from the above description.

[0066] This application claims priority based on Japanese Patent Application No. 2023-149633, filed on September 14, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. An adsorbent having a porous body containing at least magnesium oxide, wherein the magnesium oxide content in the porous body exceeds 9 mass%.

2. The adsorbent of claim 1, wherein said porous body further comprises aluminum oxide.

3. An adsorbent as described in claim 1 or 2, wherein the sum of the pore volume Vp(BJH) calculated by the BJH method and the pore volume Vp(MP) calculated by the MP method is 0.40 mL / g or more and 2.00 mL / g or less, and the proportion of Vp(BJH) in the sum of Vp(BJH) and Vp(MP) is 50% or more.

4. An adsorbent material according to any one of claims 1 to 3, wherein the magnesium oxide content in the porous body is 15 mass% or more.

5. The adsorbent according to any one of claims 1 to 4, wherein the adsorbent is an adsorbent for perfluoroalkyl and polyfluoroalkyl compounds.

6. The adsorbent according to any one of claims 1 to 4, wherein the porous body is substantially free of carbon material.

7. The adsorbent according to claim 5, wherein said porous body is substantially free of carbon material.

8. An adsorbent according to any one of claims 1 to 7, wherein the total content of magnesium oxide and aluminum oxide in the porous body is 90 mass% or more.

9. The adsorbent according to any one of claims 1 to 7, wherein the porous body consists essentially of magnesium oxide and aluminum oxide.

10. An adsorbent material described in any one of claims 1 to 7, wherein the magnesium oxide content in the porous body is 90 mass% or more.

11. The adsorbent according to any one of claims 1 to 7, wherein the porous body consists essentially of magnesium oxide.

12. A method of adsorption comprising adsorbing perfluoroalkyl and polyfluoroalkyl compounds with the adsorbent according to any one of claims 1 to 11.

13. A method for producing an adsorbent according to any one of claims 1 to 12, comprising the steps of mixing at least a magnesium oxide precursor with water to form a granule, and calcining the granule.

14. The method for producing an adsorbent according to claim 13, wherein the granules are formed by mixing a magnesium oxide precursor, an aluminum oxide precursor, and water, and granulating the mixture.

15. The adsorbent according to claim 13 or 14, wherein the granules are substantially free of carbon material.

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