Adsorbent and method for producing the same, adsorption sheet, separation membrane, and hemodialysis device

Abstract

Provided is an adsorption element that includes MXene and that has exceptional adsorption performance with respect to, e.g., polar organic compounds. The adsorption element includes: particles of a layered material including at least one layer; and one or more types of metal atoms selected from the group consisting of Al, Mg, Ca, Ba, Fe, Zn, Mn, and Cu. The layer includes a layer body represented by formula MmXn (in the formula, M represents at least one metal in group 3, 4, 5, 6, or 7, X represents a carbon atom, a nitrogen atom, or a combination thereof, n is 1-4 (inclusive), and m is greater than n but not greater than 5), and a modification or a terminal T (where T represents at least one selected from the group consisting of hydroxyl groups, fluorine atoms, chlorine atoms, oxygen atoms, and hydrogen atoms) present on the surface of the layer body. The M in the layer, and at least one selected from the group consisting of chlorine atoms, phosphorus atoms, iodine atoms, and sulfur atoms, are bonded together.

Description

Technical Field

[0001] The present disclosure relates to an adsorbent, a method for producing the same, an adsorption sheet, a separation membrane, and an artificial dialysis device.

Background Art

[0002] In recent years, MXene has attracted attention as a novel material. MXene is a kind of so-called two-dimensional material and is a layered material having a form of one or more layers, as will be described later. Generally, MXene has a form of particles of such a layered material (also referred to as MXene particles, which may include powders, flakes, nanosheets, etc.).

[0003] Currently, various studies are being conducted on the application of MXene to various uses such as electronic devices and medical devices. For example, in Non-Patent Document 1 and Non-Patent Document 2, it is shown that Mg + and Ca 2+ are intercalated between the layers of MXene by ion-exchanging with Li 2+ and Mg 2+ and Ca 2+ respectively. Further, Non-Patent Document 2 shows the intercalation of Na and K and electrodes using MXene. Furthermore, Patent Document 1 shows a method of intercalating Mg 2+ and Ca 2+ by adding MgF2 and CaF2 during etching. For the above applications, it is required to enhance the adsorption performance of MXene. In addition, as an application other than electrodes, Non-Patent Document 3 shows the use of MXene for urea removal in dialysis.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] As described in Non-Patent Document 3, in recent years, research has been conducted on using MXene as an adsorbent, but it is difficult to say that the adsorption performance is sufficient in the conventional technology. The present disclosure has been made in view of the above circumstances, and its object is to provide an adsorbent having excellent adsorption performance.

Means for Solving the Problems

[0007] According to one gist of the present invention, it includes particles of a layered material including one or more layers and one or more metal atoms selected from the group consisting of Al, Mg, Ca, Ba, Fe, Zn, Mn, and Cu, wherein the layer has the following formula: M m X n (wherein M is at least one metal of Groups 3, 4, 5, 6, and 7, X is a carbon atom, a nitrogen atom, or a combination thereof, n is 1 or more and 4 or less, m is greater than n and 5 or less) and a layer body represented by the formula, and a modification or termination T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer body, There is provided an adsorbent in which M of the layer is bonded to at least one selected from the group consisting of a chlorine atom, a phosphorus atom, an iodine atom, and a sulfur atom.

[0008] According to another gist of the present invention, (a) The following formula: M m AX n (wherein M is at least one metal of Groups 3, 4, 5, 6, and 7, X is a carbon atom, a nitrogen atom, or a combination thereof, A is at least one element of Groups 12, 13, 14, 15, and 16, n is 1 or more and 4 or less, m is greater than n and 5 or less) preparing a precursor represented by the formula, (b) performing an etching treatment to remove at least a part of A atoms from the precursor using an etching solution containing one or more of HCl, H3PO4, HI, and H2SO4, (c) pickling the etched product obtained by the etching treatment, (d) washing the pickled product obtained by the pickling with water to adjust the pH of the pickled product. (e) A step of mixing the water-washed product obtained by the water washing with a compound containing at least one metal atom selected from the group consisting of Al, Mg, Ca, Ba, Fe, Zn, Mn, and Cu, to perform a metal atom intercalation treatment, and (f) Washing the metal atom intercalation-treated product obtained by the metal atom intercalation treatment with water to obtain an adsorbent A method for producing an adsorbent is provided, which includes the above steps.

Advantages of the Invention

[0009] According to the present disclosure, the adsorbent is formed of a predetermined layered material (also referred to as "MXene" in this specification), contains at least one metal atom selected from the group consisting of Al, Mg, Ca, Ba, Fe, Zn, Mn, and Cu, and at least one selected from the group consisting of a chlorine atom, a phosphorus atom, an iodine atom, and a sulfur atom is bonded to M in MXene. Thereby, an adsorbent containing MXene and having excellent adsorption performance is provided.

[0010] Also according to the present invention, (a) preparing a predetermined precursor, (b) performing an etching treatment to remove at least part of A atoms from the precursor using a predetermined etching solution, (c) pickling the etching-treated product obtained by the etching treatment, (d) washing the pickling-treated product obtained by the pickling with water to adjust the pH of the pickling-treated product, (e) a step of mixing the water-washed product obtained by the water washing with a compound containing at least one metal atom selected from the group consisting of Al, Mg, Ca, Ba, Fe, Zn, Mn, and Cu to perform a metal atom intercalation treatment, and (f) washing the metal atom intercalation-treated product obtained by the metal atom intercalation treatment with water, so that at least one selected from the group consisting of a chlorine atom, a phosphorus atom, an iodine atom, and a sulfur atom is bonded to M in MXene containing the above metal atoms, and an adsorbent having excellent adsorption performance for polar organic compounds, for example, can be produced.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0012] (Embodiment 1: Adsorbent) Hereinafter, the adsorbent in one embodiment of the present invention will be described in detail, but the present invention is not limited to such an embodiment.

[0013] The adsorbent in this embodiment includes particles of a layered material containing one or more layers and one or more metal atoms selected from the group consisting of Al, Mg, Ca, Ba, Fe, Zn, Mn, and Cu, wherein the layer has the following formula: M m X n (wherein M is at least one metal of Group 3, 4, 5, 6, or 7, X is a carbon atom, a nitrogen atom, or a combination thereof, n is 1 or more and 4 or less, m is greater than n and 5 or less) and includes a layer main body represented by the formula and a modification or termination T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer main body, and at least one selected from the group consisting of a chlorine atom, a phosphorus atom, an iodine atom, and a sulfur atom is bonded to M of the layer.

[0014] The above-mentioned layered material can be understood as a layered compound and is also represented as "M m X n T s ", where s is an arbitrary number, and conventionally, x or z may be used instead of s. Typically, n can be 1, 2, 3, or 4, but is not limited thereto.

[0015] In the above formula of MXene, M is preferably at least one selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and Mn, and more preferably at least one selected from the group consisting of Ti, V, Cr, and Mo.

[0016] MXene has the above formula: M m X n which is known to be expressed as follows. Sc2C, Ti2C, Ti2N, Zr2C, Zr2N, Hf2C, Hf2N, V2C, V2N, Nb2C, Ta2C, Cr2C, Cr2N, Mo2C, Mo 1.3 C, Cr 1.3 C, (Ti,V)2C, (Ti,Nb)2C, W2C, W 1.3 C, Mo2N, Nb 1.3 C, Mo 1.3 Y 0.6 C (in the above formula, "1.3" and "0.6" respectively mean about 1.3 (= 4 / 3) and about 0.6 (= 2 / 3).), Ti3C2, Ti3N2, Ti3(CN), Zr3C2, (Ti,V)3C2, (Ti2Nb)C2, (Ti2Ta)C2, (Ti2Mn)C2, Hf3C2, (Hf2V)C2, (Hf2Mn)C2, (V2Ti)C2, (Cr2Ti)C2, (Cr2V)C2, (Cr2Nb)C2, (Cr2Ta)C2, (Mo2Sc)C2, (Mo2Ti)C2, (Mo2Zr)C2, (Mo2Hf)C2, (Mo2V)C2, (Mo2Nb)C2, (Mo2Ta)C2, (W2Ti)C2, (W2Zr)C2, (W2Hf)C2, Ti4N3, V4C3, Nb4C3, Ta4C3, (Ti,Nb)4C3, (Nb,Zr)4C3, (Ti2Nb2)C3, (Ti2Ta2)C3, (V2Ti2)C3, (V2Nb2)C3, (V2Ta2)C3, (Nb2Ta2)C3, (Cr2Ti2)C3, (Cr2V2)C3, (Cr2Nb2)C3, (Cr2Ta2)C3, (Mo2Ti2)C3, (Mo2Zr2)C3, (Mo2Hf2)C3, (Mo2V2)C3, (Mo2Nb2)C3, (Mo2Ta2)C3, (W2Ti2)C3, (W2Zr2)C3, (W2Hf2)C3, (Mo 2.7 V 1.3 )C3 (In the above formula, "2.7" and "1.3" respectively mean approximately 2.7 (= 8 / 3) and approximately 1.3 (= 4 / 3).)

[0017] Typically, in the above formula, M can be titanium or vanadium, and X can be a carbon atom or a nitrogen atom. For example, the MAX phase is Ti3AlC2, and the MXene is Ti3C2T s is (in other words, M is Ti, X is C, n is 2, and m is 3).

[0018] In the present invention, the MXene may contain a relatively small amount of the remaining A atoms, for example, 10% by mass or less based on the original A atoms. The remaining amount of A atoms can preferably be 8% by mass or less, more preferably 6% by mass or less. However, even if the remaining amount of A atoms exceeds 10% by mass, there may be no problem depending on the use and usage conditions of the adsorbent.

[0019] Hereinafter, the MXene particles corresponding to the skeleton of the adsorbent according to the present embodiment will be described with reference to FIG. 1. FIG. 1 does not illustrate that it contains a specific metal element and that at least one selected from the group consisting of a chlorine atom, a phosphorus atom, an iodine atom, and a sulfur atom is bonded to M of the layer.

[0020] The adsorbent of the present embodiment is an aggregate containing one layer of MXene 10a (single-layer MXene) schematically illustrated in FIG. 1(a). More specifically, MXene 10a is M m X n represented by the layer main body (M m X n layer) 1a and a modification or termination T3a, 5a present on the surface of the layer main body 1a (more specifically, at least one of the two surfaces facing each other in each layer). Thus, the MXene layer 7a is also represented as “M m X n T s ”, and s is an arbitrary number.

[0021] The adsorbent of the present embodiment may include a plurality of layers together with one layer. Examples of the plurality of layers of MXene (multi-layer MXene) include, but are not limited to, two layers of MXene 10b schematically shown in FIG. 1(b). 1b, 3b, 5b, 7b in FIG. 1(b) are the same as 1a, 3a, 5a, 7a in FIG. 1(a) described above. Two adjacent MXene layers (for example, 7a and 7b) of the multi-layer MXene do not necessarily have to be completely separated and may be in partial contact. The MXene 10a is one in which the multi-layer MXene 10b is individually separated and exists as one layer, and there may be a case where the non-separated multi-layer MXene 10b remains and is a mixture of the single-layer MXene 10a and the multi-layer MXene 10b. The adsorbent of the present embodiment is preferably formed of particles of a layered material containing a plurality of layers, that is, multi-layer MXene. By being formed of particles of a layered material containing a plurality of layers, a large amount of the target adsorbate can be adsorbed between the plurality of layers, and the adsorption performance can be enhanced.

[0022] Although not limiting the present embodiment, the thickness of each layer of MXene (corresponding to the above-mentioned MXene layers 7a and 7b) is, for example, 0.8 nm or more and 5 nm or less, particularly 0.8 nm or more and 3 nm or less (which may mainly vary depending on the number of M atomic layers contained in each layer). For each individual laminate of the multilayer MXene that can be included, the interlayer distance (or void dimension, indicated by Δd in FIG. 1(b)) is, for example, 0.8 nm or more and 10 nm or less, particularly 0.8 nm or more and 5 nm or less, more particularly about 1 nm, and the total number of layers can be 2 or more and 20,000 or less.

[0023] The adsorbent of the present embodiment contains one or more metal atoms selected from the group consisting of Al, Mg, Ca, Ba, Fe, Zn, Mn, and Cu. To distinguish the metal atoms from the metal atoms constituting MXene, they are referred to as "specific metal atoms", and those containing particles of the layered material and specific metal atoms may be referred to as "MXene containing specific metal atoms" to distinguish them from MXene not containing specific metal atoms.

[0024] The above specific metal atoms may be derived from an intercalator used for the intercalation of the specific metal atoms. By the intercalation of the specific metal atoms, it is preferable that the above specific metal atoms are preferably present between the layers of MXene. The specific metal atoms may be in the state of metal ions in MXene. That is, as divalent metal ions, they may be present between the layers of MXene. When the above specific metal atoms are present between the layers of MXene and exhibit the effect of a pillar supporting a wide interlayer space, it becomes easier for the substance to be adsorbed to be inserted between the MXene layers. As a result, a large amount of the substance to be adsorbed can be adsorbed, and the adsorption performance can be enhanced, which is preferable. For example, when the substance to be adsorbed is urea, the adsorbent has high urea adsorption characteristics and is excellent as a material for artificial dialysis. Furthermore, for example, when the substance to be adsorbed is a dye typified by methylene blue, it is excellent as an adsorbent for removing dyes from industrial water. Also, when specific metal atoms such as Mg and Ca are present between the layers of MXene and the interlayer space of MXene expands, impurities between the layers of MXene, such as acidic substances used during production, can be easily removed during the production stage, and the resulting adsorbent can suppress the pH change of the solution due to acidic substances in the adsorbent when it comes into contact with the solution.

[0025] During the production of the adsorbent, by performing the intercalation of the above specific metal atoms, the above specific metal atoms are inserted between the layers of MXene, and the interlayer distance becomes wider, making the interlayer distance more appropriate for the size of the substance to be adsorbed, and it is considered that the adsorption performance is enhanced. The above specific metal atoms are elements that have a charge of 2 or more and can form a water-soluble compound.

[0026] The content of the specific metal atoms (total content in the case of two or more types) can be 0.001 mass% or more and 3.0 mass% or less.

[0027] In consideration of biocompatibility, the specific metal atom preferably contains one or more selected from the group consisting of Mg, Ca, Fe, Zn, and Mn. More preferably, the specific metal atom is composed of one or more selected from the group consisting of Mg, Ca, Fe, Zn, and Mn. It is more preferable that the specific metal atom contains one or more of Mg and Ca, for example, from the viewpoint of further enhancing biocompatibility. Particularly preferably, the specific metal atom is Mg and / or Ca.

[0028] The total content of one or more of Mg and Ca in the specific metal atom is preferably 0.001% by mass or more and 1.5% by mass or less. From the viewpoint of further enhancing biocompatibility, it is preferable that the specific metal atom is less.

[0029] For example, in the case of an adsorbent that does not contain Li as described later and contains one or more of Mg and Ca as the specific metal atom, Mg and Ca are present as ions, which is preferable because it has high biocompatibility, and Mg 2+ and Ca 2+ increase the interlayer distance, and as a result, the interlayer distance becomes appropriate for the size of urea molecules, so that urea easily enters between the MXene layers, which is preferable.

[0030] In the adsorbent of the present embodiment, at least one selected from the group consisting of the M of the layer and a chlorine atom, a phosphorus atom, an iodine atom, and a sulfur atom is bonded. The chlorine atom, phosphorus atom, iodine atom, and sulfur atom may be derived from HCl (hydrochloric acid), H3PO4 (phosphoric acid), HI (hydrogen iodide), and H2SO4 (sulfuric acid), respectively, contained in the etching solution used during the etching treatment for the MAX phase, which is a precursor of MXene. That is, the chlorine atom in the adsorbent of the present embodiment is preferably Cl - bonded to the M of the layer, the phosphorus atom is preferably a phosphorus atom constituting PO4 3- bonded to the M of the layer, and the iodine atom in the adsorbent of the present embodiment is preferably I bonded to the M of the layer. Also, the sulfur atom in the adsorbent of the present embodiment is SO4 bonded to the M of the layer2- It is preferably a sulfur atom that constitutes it.

[0031] (Li content of the adsorbent) The adsorbent of the present embodiment preferably has a Li content, for example, below the quantification limit, for example, a Li content of 0.0001 mass% or less (including 0 mass%). By suppressing the Li content of the adsorbent within the above range, the adsorbent of the present embodiment can be adopted for applications that require biocompatibility, such as a separation membrane in an artificial dialysis device. The Li content can be measured, for example, by ICP-AES using inductively coupled plasma optical emission spectrometry.

[0032] (Interlayer distance of the adsorbent) As described above, in the adsorbent of the present embodiment, it is considered that the specific metal atoms are preferably inserted between the layers of MXene and the interlayer is widened. M m X n When it is Ti3C2O2 (O-term) represented by Ti3C2, the crystal structure is as schematically shown in FIG. 2 (in FIG. 2, 20 is a titanium atom, 21 is an oxygen atom, and other constituent atoms are not shown), and it is considered that the distance between the layers indicated by the double-headed arrow in this FIG. 2 is widened. The above distance can be determined by the position of the low-angle peak of 10° (deg) or less corresponding to the (002) plane of MXene in the XRD profile obtained by X-ray diffraction measurement. The lower the angle of the peak in the XRD profile, the wider the interlayer distance. In the adsorbent of the present embodiment, the peak of the (002) plane obtained by X-ray diffraction measurement is preferably less than 8.0°. The peak is more preferably 7.0° or less. The lower limit of the peak position is about 5.0°. The peak refers to the peak top. The X-ray diffraction measurement may be performed under the conditions shown in the examples described later.

[0033] When the adsorbent of the present embodiment is M m X nWhen it has MXene represented by Ti3C2 and specific metal atoms, the interlayer distance obtained from the results of the above XRD is, for example, 12.0 Å or more, preferably 12.5 Å or more, more preferably 13.0 Å or more, and the upper limit of the interlayer distance can be, for example, approximately 17.5 Å. Due to the widening of the interlayer distance, as a result, the interlayer distance becomes an appropriate value with respect to the size of urea molecules, and it is considered that the adsorption performance has increased. In particular, since the interlayer distance in the above range is, for example, a size suitable for adsorbing uremic toxins that need to be removed by artificial dialysis, especially urea, the adsorbent of the present embodiment is suitable for adsorbing the urea.

[0034] (Adsorbent formed of a composite material) Examples of the adsorbent of the present embodiment include those further containing one or more materials among ceramic, metal, and resin materials. For example, as illustrated later, when the adsorbent of the present embodiment is used for urea adsorption in artificial dialysis, by making it a composite material (composite) of the specific metal atom-containing MXene according to the present embodiment and one or more materials among ceramic, metal, and resin materials, an adsorbent that stably exhibits adsorption performance, for example, urea adsorption performance, can be realized.

[0035] Examples of the above ceramic include metal oxides such as silica, alumina, zirconia, titania, magnesia, cerium oxide, zinc oxide, barium titanate-based, hexaferrite, and mullite, and non-oxide ceramics such as silicon nitride, titanium nitride, aluminum nitride, silicon carbide, titanium carbide, tungsten carbide, boron carbide, and titanium boride. Examples of the above metal include iron, titanium, magnesium, aluminum, and alloys based on these.

[0036] Examples of the resin material (polymer) include cellulose-based and synthetic polymer-based materials. Examples of the polymer include hydrophilic polymers (including those obtained by blending a hydrophilic aid with a hydrophobic polymer to exhibit hydrophilicity and those obtained by hydrophilizing the surface of a hydrophobic polymer or the like). Examples of the hydrophilic polymer preferably include one or more selected from the group consisting of polysulfone, cellulose acetate, regenerated cellulose, polyethersulfone, water-soluble polyurethane, polyvinyl alcohol, sodium alginate, acrylic acid-based water-soluble polymers, polyacrylamide, polyaniline sulfonic acid, and nylon.

[0037] As the hydrophilic polymer, for example, a hydrophilic polymer having a polar group, wherein the polar group is a group that forms a hydrogen bond with the modification or termination T of the layer, is preferably used. Examples of the polymer preferably include one or more polymers selected from the group consisting of water-soluble polyurethane, polyvinyl alcohol, sodium alginate, acrylic acid-based water-soluble polymers, polyacrylamide, polyaniline sulfonic acid, and nylon. Among these, one or more polymers selected from the group consisting of water-soluble polyurethane, polyvinyl alcohol, and sodium alginate are more preferable, and water-soluble polyurethane is even more preferable.

[0038] When an adsorbent formed of a composite material is used, for example, for biological applications, examples of the polymer constituting the composite material include polymer polymers used for hemodialysis and hemofiltration. Specifically, examples include polymethyl methacrylate, polyacrylonitrile, cellulose, cellulose acetate, polysulfone, polyvinyl alcohol, or vinyl alcohol copolymers such as copolymers of polyvinyl alcohol and ethylene. Preferably, it is one or more of polysulfone, polymethyl methacrylate, and cellulose acetate. More preferably, polysulfone and polymethyl methacrylate are used.

[0039] The proportion of the polymer contained in the composite material can be appropriately set according to the application. For example, the proportion of the polymer can be more than 0% by volume, for example, 80% by volume or less, and further 50% by volume or less, further 30% by volume or less, further 10% by volume or less, and even further 5% by volume or less, based on the proportion in the adsorbent (when dry).

[0040] The method for manufacturing the adsorbent formed of the composite material is not particularly limited. When the adsorbent of the present embodiment contains a polymer and is an adsorbent having a sheet-like form, for example, as exemplified below, a specific metal atom-containing MXene and a polymer can be mixed to form a coating film.

[0041] First, a specific metal atom-containing MXene aqueous dispersion, a specific metal atom-containing MXene organic solvent dispersion, or a specific metal atom-containing MXene powder in which particles formed of a specific metal atom-containing MXene are present in a dispersion medium, and a polymer may be mixed. The dispersion medium of the specific metal atom-containing MXene aqueous dispersion is typically water, and in some cases, in addition to water, other liquid substances may be contained in a relatively small amount (for example, 30% by mass or less, preferably 20% by mass or less based on the total).

[0042] The stirring of the specific metal atom-containing MXene particles and the polymer can be performed using a dispersion device such as a homogenizer, a propeller stirrer, a thin-film swirling stirrer, a planetary mixer, a mechanical shaker, or a vortex mixer.

[0043] The slurry, which is a mixture of the specific metal atom-containing MXene particles and the polymer, may be applied to a substrate (for example, a substrate), and the coating method is not limited. For example, methods such as spray coating using a nozzle such as a one-fluid nozzle, a two-fluid nozzle, or an airbrush, slit coating using a table coater, a comma coater, or a bar coater, screen printing, metal mask printing, spin coating, dipping, or coating by dropping can be mentioned.

[0044] The above coating and drying may be repeated a plurality of times as necessary until a film of a desired thickness is obtained. The drying and curing may be performed, for example, at a temperature of 400 degrees or lower using an atmospheric oven or a vacuum oven.

[0045] When the adsorbent of the present embodiment is a composite material containing ceramic or metal, as a manufacturing method thereof, for example, particulate specific metal atom-containing MXene and, for example, particulate ceramic or metal are mixed and heated at a low temperature at which the composition of the specific metal atom-containing MXene can be maintained to form an adsorbent.

[0046] (Shape of adsorbent) The shape of the adsorbent of the present embodiment is not limited. The shape of the adsorbent may be one having a thickness, a rectangular parallelepiped, a sphere, a polyhedron, etc., other than the case of having a sheet-like form such as the film.

[0047] (Adsorption sheet) A preferable embodiment of the adsorbent of the present embodiment is an adsorption sheet. The adsorption sheet is, in addition to the adsorbent of the present embodiment, that is, an adsorption sheet formed of specific metal element-containing MXene or a composite material containing the same, an adsorption sheet formed on the surface of a substrate formed of one or more materials among ceramic, metal, and resin materials of the present embodiment. As the ceramic, metal, and resin materials, the materials mentioned in the description of the above composite material can be used. Among them, an adsorption sheet in which the adsorbent of the present embodiment is formed on a substrate formed of a resin material, preferably the above-mentioned polymer, is preferable. The mode of the adsorbent of the present embodiment on the substrate may be such that the adsorbent is formed on one surface of the substrate, for example, by coating or the like, or may be formed on at least a part of the substrate. As a method for forming the adsorbent on the substrate, for example, generally used coating methods such as dipping, brushing, roller, roll coater, air spray, airless spray, curtain flow coater, roller curtain coater, die coater, and electrostatic coating can be used. The thickness of the adsorption sheet and the thickness of the substrate can be appropriately set according to the application.

[0048] (Use of the adsorbent) One of the uses of the adsorbent of the present embodiment is to be used for adsorbing polar organic compounds. A polar organic compound is a general term for organic compounds having polarity, and refers to a compound having a polar group such as an OH group, a NO2 group, an NH group, an NH2 group, or a COOH group, and when mixed with water, a hydrogen atom in a water molecule and these polar groups can form a hydrogen bond. Among the above polar organic compounds, polar solvents such as alcohols having a hydroxyl group, compounds having an amino group, ammonia, etc. can be mentioned as adsorption targets. The adsorbent of the present embodiment can be used for adsorbing a compound having one or more of a hydroxyl group and an amino group, and ammonia. Among the compounds having one or more of the hydroxyl group and the amino group, examples of the compound having a hydroxyl group include monohydric alcohols having 1 to 22 carbon atoms; polyhydric phenols; polyhydric alcohols such as ethylene glycol, propylene glycol, and glycerin; alkanolamines such as triethanolamine; sugars such as xylose and glucose. Examples of the compound having an amino group include monoamines such as methylamine and dimethylamine; diamines such as ethylenediamine; polyamines such as diethylenetriamine; aromatic amines such as aniline; amino acids such as valine and leucine, urea, uric acid, urate, creatinine, etc. Examples of the compound having both a hydroxyl group and an amino group include ethanolamine and diethanolamine.

[0049] The adsorbent of the present embodiment is preferably used for adsorbing uremic toxins such as urea, uric acid, creatinine, etc. The adsorbent of the present embodiment can be optimally used particularly for adsorbing urea.

[0050] The adsorbent of the present embodiment can be used for adsorbing and removing waste products such as urea in hemodialysis, hemofiltration, hemodiafiltration, peritoneal dialysis, etc. Further, the adsorbent of the present embodiment can be used in an artificial dialysis device for performing the above hemodialysis, hemofiltration, hemodiafiltration, peritoneal dialysis, etc.

[0051] The artificial dialysis machines are classified into, for example, hemodialysis machines and peritoneal dialysis machines. Hemodialysis machines can be divided into one-pass type (single-pass type) and circulation type. Further, the circulation type includes those using the REDY system (recirculating dialysate system) and other systems. The artificial dialysis machines can also be classified by a method of removing urea without contacting the blood through cross-flow of blood and dialysate from the patient, and a method of directly filtering the blood. Also, the one-pass type is the mainstream for peritoneal dialysis machines. The adsorbent of the present embodiment can be used for any of these hemodialysis and peritoneal dialysis, and can be used as an adsorption membrane, separation membrane, adsorbent cartridge, etc. in artificial dialysis machines such as hemodialysis machines and peritoneal dialysis machines. For example, when used in the REDY system (recirculating dialysate system), it can be mentioned that the adsorbent of the present embodiment is used in the adsorbent cartridge.

[0052] FIG. 3 schematically shows an example of an artificial dialysis machine using the adsorbent according to the present invention, which is a one-pass type hemodialysis machine. In the hemodialysis machine 40 of FIG. 3, the blood before treatment introduced from the blood inlet 41 is sent by the blood pump 43 to the blood purification device 44. On the other hand, dialysate is sent from the unused dialysate tank 48 by the dialysate pump 50 to the blood purification device 44. In the blood purification device 44, the blood in the blood passage area 46 of the blood purification device is subjected to hemodialysis, hemodiafiltration or hemofiltration by the separation membrane 45, and the substances to be removed pass through the separation membrane 45 and move to the dialysate passage area 47 of the blood purification device. The purified blood is sent to the blood outlet 42. On the other hand, the dialysate in the dialysate passage area 47 containing the substances to be removed is sent to the used dialysate tank 49. Although not shown in FIG. 3, a device including a path for supplementing the blood with drugs, proteins, etc. as needed may be provided during the feeding of the blood before and / or after treatment. Also, sensors for measuring the blood flow rate, dialysate flow rate, and, if necessary, the protein concentration in the blood may be provided. Also, on-off valves capable of opening and closing the flow path as needed may be provided in the middle of the flow paths of the blood and / or dialysate.

[0053] The separation membrane using the adsorbent of the present embodiment is suitable for the artificial dialysis separation membrane used in hemodialysis and the like. As the material constituting the separation membrane other than the adsorbent, generally, cellulose-based and synthetic polymer-based materials used in hemodialysis and the like can be mentioned. Specifically, polymethyl methacrylate, polyacrylonitrile, cellulose, cellulose acetate, polysulfone, polyvinyl alcohol, or a vinyl alcohol copolymer such as a copolymer of polyvinyl alcohol and ethylene can be mentioned. Polysulfone, polymethyl methacrylate, and cellulose acetate are preferable, and polysulfone and polymethyl methacrylate are more preferably used. The form of the artificial dialysis separation membrane is not particularly limited, and examples include a porous type, a hollow fiber type, and a flat film laminated type.

[0054] As described above, the adsorbent of the present embodiment is also suitable as an adsorbent used for adsorbing dyes. Examples of the dye include methylene blue. The adsorbent is suitable for removing methylene blue, which is a dye contained in industrial water, for example. As an embodiment using an adsorbent for adsorbing dyes, the above-mentioned adsorption sheet and the separation membrane using the adsorbent can be mentioned. The material constituting the separation membrane used for adsorbing the dye other than the adsorbent is not particularly limited and can be one or more materials among ceramic, metal, and resin materials. As these materials, the ceramic, metal, and resin materials that can be used in the above-mentioned composite material can be used.

[0055] (Embodiment 2: Method for producing adsorbent) Hereinafter, the method for producing the adsorbent in the embodiment of the present invention will be described in detail, but the present invention is not limited to such an embodiment.

[0056] The method for producing the adsorbent of the present embodiment is (a) The following formula: M m AX n (In the formula, M is at least one metal of Groups 3, 4, 5, 6, and 7, X is a carbon atom, a nitrogen atom, or a combination thereof, A is at least one element of Group 12, 13, 14, 15, or 16, n is 1 or more and 4 or less, m is greater than n and 5 or less) preparing a precursor represented by (b) performing an etching process of removing at least some of the A atoms from the precursor using an etching solution containing one or more of HCl, H3PO4, HI, and H2SO4, (c) pickling the etched product obtained by the etching process, (d) washing the pickled product obtained by the pickling with water to adjust the pH of the pickled product, (e) performing a specific metal atom intercalation process including a step of mixing the washed product obtained by the water washing with a compound containing one or more specific metal atoms selected from the group consisting of Al, Mg, Ca, Ba, Fe, Zn, Mn, and Cu, and (f) washing the specific metal atom intercalation product obtained by performing the specific metal atom intercalation process with water to obtain an adsorbent is included. By this production method, an adsorbent containing the above specific metal atoms and having excellent adsorption performance for, for example, polar organic compounds can be produced, in which M in MXene is bonded to at least one selected from the group consisting of a chlorine atom, a phosphorus atom, an iodine atom, and a sulfur atom.

[0057] In the method for producing an adsorbent according to the present embodiment, in particular, specific metal atom intercalation is performed as described above in the etching step using an etching solution containing one or more of HCl, H3PO4, HI, and H2SO4 for etching, and MXene having a large three-dimensional (Cl - , PO4 3- , I, and SO4 2- ) on the surface is utilized. By performing pickling before the intercalation of specific metal atoms to remove impurities that are inhibitory factors for intercalation, MXene in which specific metal atoms are included in the layers and having excellent adsorption performance can be easily obtained.

[0058] The following describes each step of the above manufacturing method in detail. · Step (a) First, prepare a predetermined precursor. The predetermined precursor that can be used in this embodiment is the MAX phase, which is the precursor of MXene. The following formula: M m AX n (In the formula, M is at least one metal of Groups 3, 4, 5, 6, and 7. X is a carbon atom, a nitrogen atom, or a combination thereof. A is at least one element of Groups 12, 13, 14, 15, and 16. n is 1 or more and 4 or less. m is greater than n and 5 or less.) is represented by.

[0059] The above M, X, n, and m are as described for MXene. A is at least one element of Groups 12, 13, 14, 15, and 16, usually a Group A element, typically Group IIIA and Group IVA, and more specifically, may include at least one selected from the group consisting of Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, S, and Cd, preferably Al.

[0060] The MAX phase has a crystal structure in which a layer composed of A atoms is located between two layers represented by M m X n (each X may have a crystal lattice located within the octahedral array of M). The MAX phase typically has a repeating unit in which when m = n + 1, a layer of X atoms is arranged one by one between each of the n + 1 layers of M atoms (collectively referred to as the "M m X n layer"), and a layer of A atoms (the "A atom layer") is arranged as the next layer after the n + 1th layer of M atoms, but is not limited thereto.

[0061] The above MAX phase can be manufactured by known methods. For example, TiC powder, Ti powder, and Al powder are mixed with a ball mill, and the obtained mixed powder is fired in an Ar atmosphere to obtain a fired body (block-shaped MAX phase). Thereafter, the obtained fired body can be pulverized with an end mill to obtain a powdered MAX phase for the next step.

[0062] · Step (b) An etching treatment is performed to remove at least a part of the A atoms from the precursor using an etching solution containing one or more of HCl, H3PO4, HI, and H2SO4. In the manufacturing method of the present embodiment, for the purpose of facilitating the intercalation of specific metal atoms in a later-described step (e), MXene having a large three-dimensional structure (Cl - , PO4 3- , I, and SO4 2- ) is obtained by performing etching using an etching solution containing one or more of the above HCl, H3PO4, HI, and H2SO4. Other conditions of the etching treatment are not particularly limited, and known conditions can be adopted. As described above, the etching can be further performed using an etching solution containing F - . For example, a method using an etching solution containing hydrofluoric acid and further containing these hydrochloric acids, etc., can be mentioned. In these methods, a method using a mixed solution with, for example, pure water as a solvent can be mentioned. Examples of the etched product obtained by the above etching treatment include a slurry. As the above etching solution, an etching solution satisfying at least one selected from the group consisting of a HCl concentration of 6.0 M or more, a H3PO4 concentration of 5.5 M or more, a HI concentration of 5.0 M or more, and a H2SO4 concentration of 5.0 M or more can be used. In the etching of the A atoms, a part of the M atoms may also be selectively etched together with the A atoms in some cases.

[0063] After the above etching, water washing can be appropriately performed. For example, adding water, stirring, centrifuging, etc. can be mentioned. As the stirring method, stirring using a hand shake, an automatic shaker, a share mixer, a pot mill, etc. can be mentioned. The degree of stirring such as the stirring speed and the stirring time may be adjusted according to the amount and concentration of the object to be treated. The washing with the above water may be performed once or more. Preferably, the washing with water is performed a plurality of times. For example, specifically, (i) adding water to (the etched product or the remaining precipitate obtained in the following (iii)) and stirring, (ii) centrifuging the stirred product, (iii) discarding the supernatant after centrifugation, and steps (i) to (iii) can be performed within a range of 2 times or more, for example, 10 times or less.

[0064] · Step (c) The etched product obtained by the above etching treatment is pickled. The acid used for the above pickling is not limited, and for example, an inorganic acid such as a mineral acid and / or an organic acid can be used. The acid is preferably only an inorganic acid or a mixed acid of an inorganic acid and an organic acid. The acid is more preferably only an inorganic acid. As the above inorganic acid, for example, one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, perchloric acid, hydroiodic acid, hydrobromic acid, hydrofluoric acid, etc. can be used. Preferably, it is one or more of hydrochloric acid and sulfuric acid. As the above organic acid, for example, acetic acid, citric acid, oxalic acid, benzoic acid, sorbic acid, etc. can be mentioned. The concentration of the acid solution to be mixed with the etched product may be adjusted according to the amount and concentration of the etched product to be treated.

[0065] In the above pickling, the etched product and the acid solution are mixed, and for example, stirring can be mentioned. As the stirring method, stirring using a hand shake, an automatic shaker, a share mixer, a pot mill, etc. can be mentioned. The degree of stirring such as the stirring speed and the stirring time may be adjusted according to the amount and concentration of the etched product to be treated.

[0066] When mixing the above acid solutions and stirring, heating may or may not be performed. The acid solutions may be mixed and stirred without heating, or stirred while heating within a range where the liquid temperature is 80°C or lower.

[0067] Step (d) The pickling treatment product obtained by the pickling is washed with water to adjust the pH of the pickling treatment product. This water washing can be performed in the same manner as the water washing after the etching described above. By performing this water washing, pH adjustment after pickling is performed. For example, the pH in the acidic region can be adjusted to, for example, about 5 or more and 8 or less. MgF2 and CaF2 used during etching in Patent Document 1 above are not preferable because they remain as insoluble compounds by adjusting the pH by water washing.

[0068] ·Step (e) A specific metal atom intercalation treatment is performed, including a step of mixing the water washing treatment product obtained by the water washing with a compound containing one or more specific metal atoms selected from the group consisting of Al, Mg, Ca, Ba, Fe, Zn, Mn, and Cu. As described above, the above specific metal atoms are larger in size than Na, K, etc., and have the effect of expanding the interlayer, so the adsorption characteristics are improved.

[0069] As the compound containing the specific metal atom, an ionic compound in which a specific metal ion is bonded to a cation can be used. For example, iodides, phosphates, sulfide salts containing sulfates, nitrates, acetates, and carboxylates of specific metal ions can be mentioned. Compounds with low solubility such as MgF2 and CaF2 as described above are not included.

[0070] The content of the compound containing the specific metal atom in the formulation for the intercalation treatment is preferably 0.001% by mass or more. The above content is more preferably 0.01% by mass or more, and still more preferably 0.1% by mass or more. On the other hand, from the perspective of dispersibility in the solution, the content of the compound containing the specific metal atom is preferably 10% by mass or less, and more preferably 1% by mass or less.

[0071] The specific method of the intercalation treatment is not particularly limited. For example, for the above-mentioned MXene in a moisture medium clay, a compound containing the above-mentioned specific metal atoms may be mixed and stirred, or allowed to stand. For example, stirring at room temperature may be mentioned. Examples of the stirring method include a method using a stirrer such as a magnetic stirrer, a method using a stirring blade, a method using a mixer, and a method using a centrifuge. The stirring time can be set according to the production scale of the adsorbent, and for example, it can be set within 12 to 24 hours.

[0072] · Step (f) The specific metal atom intercalation-treated product obtained by performing the specific metal atom intercalation treatment is washed with water to obtain an adsorbent. This water washing can be performed in the same manner as the water washing after the above-mentioned etching. For example, the slurry-like specific metal atom intercalation-treated product is centrifuged to discard the supernatant, and the remaining precipitate is washed with water repeatedly to obtain, for example, clay-like MXene in which specific metal atoms are intercalated.

[0073] According to the production method of the present embodiment, during the intercalation treatment of the above-mentioned specific metal atoms and the water washing in the above step (f), protons derived from the acidic substances used in the above etching and acid washing remaining between the layers are discharged and removed outside the layers. Therefore, the obtained adsorbent does not cause a decrease in the pH of the solution even when immersed in the solution later, and has excellent pH stability.

[0074] As described above, the adsorbent, its production method, the adsorption sheet, the separation membrane, and the artificial dialysis device in the embodiments of the present invention have been described in detail, but various modifications are possible. It should be noted that the adsorbent of the present invention may be produced by a method different from the production method in the above-described embodiments, and the production method of the adsorbent of the present invention is not limited to only providing the adsorbent in the above-described embodiments.

Example

[0075] 〔Preparation of MXene adsorbent〕 In this example, the following steps were carried out in sequence: (1) preparation of the precursor (MAX), (2) etching of the precursor, (3) water washing after etching, (4) acid washing (removal of Al residues derived from MAX), (5) water washing after acid washing, (6) intercalation of specific metal atoms, (7) washing after intercalation, and (8) freeze-drying to produce an adsorbent formed of a specific metal atom-containing MXene.

[0076] (1) Preparation of the precursor (MAX) TiC powder, Ti powder, and Al powder (all manufactured by High Purity Chemical Laboratory Co., Ltd.) were put into a ball mill containing zirconia balls at a molar ratio of 2:1:1 and mixed for 24 hours. The obtained mixed powder was fired at 1350 °C for 2 hours under an Ar atmosphere. The obtained fired body (block-shaped MAX) was pulverized with an end mill to a maximum size of 40 μm or less. Thereby, Ti3AlC2 particles were obtained as the precursor (powder-shaped MAX).

[0077] (2) Etching of the precursor Using the Ti3AlC2 particles (powder) prepared by the above method, etching was performed under the following etching conditions to obtain a solid-liquid mixture (slurry) containing a solid component derived from the Ti3AlC2 powder. In this example, it is considered that chlorine atoms are bonded to M in the layer of MXene due to the hydrochloric acid (HCl) contained in the etching solution used in this etching. (Etching conditions) · Precursor: Ti3AlC2 (passed through a 45-μm sieve) · Etching solution composition: 6 mL of 49% HF, 18 mL of H2O 36 mL of HCl (12 M) · Precursor input amount: 3.0 g · Etching container: 100 mL i-bottle · Etching temperature: 35 °C · Etching time: 24 h · Stirrer rotation speed: 400 rpm

[0078] (3) Water washing after etching The above slurry was evenly divided into three parts, inserted into three 50 mL centrifuge tubes respectively, and after centrifugation was carried out at 3500G using a centrifuge, the supernatant was discarded. 40 mL of pure water was added to the remaining precipitate in each centrifuge tube, and the operation of centrifuging again at 3500G to separate and remove the supernatant was repeated 11 times to obtain a slurry as a water-washed product.

[0079] (4) Acid washing (removal of Al residues derived from MAX) After adding 40 mL of 1M hydrochloric acid to the above slurry and stirring for 5 minutes with a shaker, centrifugation was carried out at 3500G, and the supernatant was discarded.

[0080] (5) Water washing after acid washing To the remaining precipitate in each centrifuge tube, (i) 40 mL of pure water was added, (ii) centrifugation was carried out at 3500G, and (iii) the supernatant was separated and removed. The operations of (i) to (iii) were repeated a total of 5 times. After the final centrifugation, the supernatant was discarded, and Ti3C2T s - water-moistened clay was obtained.

[0081] (6) Intercalation of specific metal atoms (Mg or Ca or Al) For the Ti3C2T s - water-moistened clay prepared by the above method, intercalation of specific metal atoms (Mg or Ca or Al) was carried out using each intercalator shown in Table 1. The detailed conditions for intercalation are as follows. In the following conditions, the stirring time was 18 hours, but the stirring time can be set according to the production scale of the MXene adsorbent, for example, it can be set between 12 and 24 hours. (Conditions for intercalation of (Mg or Ca or Al)) · Ti3C2T s - water-moistened clay (washed MXene): solid content 1.0 g · MgCl2: 2.34 g (Example 1), or CaCl2: 3.16 g (Example 2), or AlCl3: 3.15 g (Example 3) · Pure water: 20 mL · Intercalation container: 100 mL Iwaki · (Stirring) temperature: 20 °C or higher and 25 °C or lower (room temperature) · (Stirring) time: 18 hours · Stirrer rotation speed: 800 rpm

[0082] (7) Washing with water after intercalation of Mg or Ca or Al The slurry obtained by intercalating with the above Mg or Ca or Al was transferred to centrifuge tubes respectively, (i) 40 mL of pure water was added, (ii) centrifugation was carried out at 3500 G using a centrifuge, and (iii) the supernatant was separated and removed. The operations of (i) to (iii) were repeated a total of 5 times to remove excess Mg or Ca or Al, and each MXene clay intercalated with Ma or Ca or Al was obtained. The filtration film (MXene film) used for the following XRD measurement was obtained by suction filtration using the above MXene clay. After filtration, vacuum drying was carried out at 80 °C for 24 hours to prepare the MXene film. A membrane filter (Durapore, pore size 0.45 μm, manufactured by Merck KGaA) was used as the filter for suction filtration.

[0083] (8) Drying Each of the above MXene clays was frozen at -40 °C for 5 hours and then dried in a freeze dryer for 24 hours to obtain the MXene dry powders of Example 1, Example 2 and Example 3. This dry powder was used as an adsorbent for MXene.

[0084] As comparative examples, an adsorbent of Comparative Example 1 manufactured in the same manner as above except that Na was used, an adsorbent of Comparative Example 2 manufactured in the same manner as above except that K was used, and an adsorbent of Comparative Example 3 manufactured by the method described in Non-Patent Document 1, that is, without using hydrochloric acid for etching and without intercalation, were also prepared.

[0085] [Evaluation of MXene adsorbent] [Evaluation of interlayer distance] The interlayer distance of MXene constituting the adsorbent was measured. More specifically, under the following conditions, XRD measurements of the adsorbents of Examples 1 to 3 and Comparative Examples 1 and 2 were performed under the following conditions to obtain two-dimensional X-ray diffraction images of the MXene film. The results of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Fig. 4.

[0086] (XRD Measurement Conditions) · Measuring device: MiniFlex600 manufactured by Rigaku Corporation · Conditions Light source: Cu tube target Characteristic X-ray: CuKα = 1.54 Å Measurement range: 3 degrees - 20 degrees Step: 50 step / degree

[0087] As a result of calculating the interlayer distance from the above XRD measurement results, it was 13.5 Å in Example 1, 14.9 Å in Example 2, and 13.0 Å in Example 3. It was 11.8 Å in Comparative Example 1 and also 11.8 Å in Comparative Example 2.

[0088] From Fig. 4 and the calculated results of the above interlayer distance, in Examples 1 to 3, intercalation of Mg, Ca, and Al was performed respectively, so the peak of the (002) plane was on the low-angle side and the interlayer expanded. On the other hand, in Comparative Examples 1 and 2, intercalation of Na and K was performed respectively, but since these atoms are smaller in size than the above Mg and Ca, the interlayer distance did not expand sufficiently.

[0089] [Measurement of the content of specific metal atoms (Mg, Ca, Al) in MXene] The MXene was solubilized by an alkali fusion method, and the Mg content in the MXene of Example 1, the Ca content in the MXene of Example 2, and the Al content in the MXene of Example 3 (all corresponding to the residual amount of the intercalator) were measured by ICP-AES using inductively coupled plasma optical emission spectrometry (using iCAP7400 manufactured by Thermo Fisher Scientific). As a result, in Example 1, the Mg content was 0.78% by mass, in Example 2, the Ca content was 1.37% by mass, and in Example 3, the Al content was 0.58% by weight. In addition, it was separately confirmed that in all examples, the Li content was below the quantification limit, that is, 0.0001% by mass or less.

[0090] [Evaluation of the amount of acidic substances between layers] The pH when the adsorbent was immersed in pure water was measured to evaluate the presence or absence of the outflow of acidic substances that could be inserted between layers during the manufacturing process. As a result, in the case of Comparative Example 3 without an intercalator, the pH of the immersed pure water was 3.59, while the pH of Example 1 (intercalator is Mg) was 5.34, the pH of Example 2 (intercalator is Ca) was 5.15, and the pH of Example 3 (intercalator is Al) was 5.12. From these results, in the case of Comparative Example 3 without an intercalator, the acidic substances inserted between layers during the manufacturing process of the adsorbent flowed out after the manufacture of the adsorbent, showing strong acidity. In the case of Examples 1 to 3, since the space between layers of the adsorbent was large, it was considered that the acidic substances used in the manufacturing process were easily removed during manufacture. As a result, the decrease in pH when the adsorbent was immersed in pure water could be suppressed.

[0091] [Evaluation of adsorption performance] Using the adsorbents of Examples 1 to 3 and Comparative Examples 1 to 3 above, the adsorption amount of the adsorption target substance (urea) was measured as follows, and the adsorption performance of the adsorbent was evaluated.

[0092] (1) Preparation of urea solution 0.5 g of urea was weighed and added to 100 mL of pure water, and this was diluted 100 times to prepare a urea solution with a concentration of 5 mg / dL.

[0093] (2) Preparation of the assay kit solution Using a bioassay kit (product name: DIUR-100) manufactured by Funakoshi Co., Ltd., the solution A and solution B of the kit were mixed in equal volumes to prepare an assay kit solution.

[0094] (3) Preparation of a solution (urea solution) containing the substance to be adsorbed 250 mL of the urea solution prepared in the above procedure (1) was poured into a 500 mL beaker, and heated and stirred at a rotation speed of 400 rpm and a liquid temperature of 37 °C using a hot stirrer to prepare a solution containing urea, which is the substance to be adsorbed. Six such urea solutions were prepared for each example.

[0095] (4) Urea adsorption and sample sampling 0.1 g of the adsorbents of Examples 1 to 3 and Comparative Examples 1 to 3 above were respectively put into the urea solution prepared in procedure (3) and stirred with a hot stirrer for 30 minutes. Then, the solution after standing was sampled with a 10 mL pipette each, and the adsorbent floating under the conditions of 20,000 rpm and 10 minutes was sedimented and separated using a centrifuge, and 250 μL of the supernatant was sampled.

[0096] (5) Dropwise addition of the assay kit solution 1250 μL of the assay kit solution prepared in procedure (2) was added to the above supernatant and allowed to stand for 50 minutes.

[0097] (6) Measurement of absorbance First, for preparing a calibration curve, a urea solution without the adsorbent and a solution obtained by diluting this urea solution without the adsorbent by two-fold were prepared. Then, the absorbance of each solution was measured to prepare a calibration curve. Next, the absorbance of the sample prepared in procedure (5) was measured, and each absorbance was compared with the calibration curve to obtain the concentration of urea remaining unadsorbed in the solution. From this urea concentration, the urea adsorption amount (the amount of urea per 1 g of the adsorbent (mg)) was calculated. The results are shown in Table 1.

[0098]

Table 1

[0099] From the above results, when Na or K is used, the interlayer distance is small, and Na and K are present at the molecular adsorption sites, which inhibits adsorption. Therefore, it is considered that the adsorption performance is lower than that of Comparative Example 3 without an intercalator. On the other hand, in Examples 1, 2, and 3 using Mg, Ca, and Al as intercalators, respectively, a MXene structure with an interlayer distance suitable for the urea molecular size was obtained, and it is considered that this exhibited high adsorption performance for urea.

[0100] In Examples 1, 2, and 3 above, Mg 2+ , Ca 2+ , Al 3+ is intercalated between the MXene layers. However, since Li is not used in the manufacturing process of the adsorbent, it does not contain Li. In the technologies of Non-Patent Document 1 and Non-Patent Document 2, it is difficult to sufficiently reduce the Li content. However, according to the adsorbent of the present embodiment, it can also be applied to applications where it is necessary to reduce Li as much as possible. Furthermore, as described in Patent Document 1, when MgF2 or CaF2 is used during etching, these compounds have low solubility and can remain as impurities in the material. Therefore, for example, when the remaining of the above compounds is not allowed, further improvement is considered necessary. However, according to the adsorbent of the present embodiment, hardly soluble impurities such as MgF2 and CaF2 are not included either. Therefore, in particular, an adsorbent using Mg or Ca as an intercalator has excellent biocompatibility. Furthermore, as described above, the adsorbents of Examples 1 to 3 do not contain much acidic substances used in manufacturing, etc. Therefore, when the adsorbent is immersed in a solution, the decrease in the pH of the solution is suppressed, and it also has excellent pH stability.

[0101] [Evaluation of Adsorption Performance of Dye (Methylene Blue)] Using the MXene of Examples 1 to 3 and Comparative Examples 1 to 3 above, the adsorption target was methylene blue as an example of a dye, and an adsorption evaluation was performed.

[0102] (1) Preparation of Methylene Blue Solution Weighed 0.1 g of methylene blue and added it to 2 L of pure water to prepare a urea solution with a concentration of 5 mg / L.

[0103] (2) Preparation of a solution (urea solution) containing the substance to be adsorbed Put 250 mL of the methylene blue solution prepared in the above procedure (7) into a 500 mL beaker, and with a stirrer, perform heating and stirring at a rotation speed of 400 rpm and a liquid temperature of 20 °C to prepare a solution containing methylene blue, which is the substance to be adsorbed. Six of these urea solutions were prepared for each example.

[0104] (3) Urea adsorption, sample sampling Put 0.01 g of the adsorbents of the above Examples 1 to 3 and Comparative Examples 1 to 3 respectively into the methylene blue solution prepared in procedure (8), and stir with a stirrer for 30 minutes. Then, after standing, collect the solution with a 10 mL pipette, and use a centrifuge to sediment and separate the floating adsorbent under the conditions of 3500 G for 5 minutes, and sample 1000 μL of the supernatant.

[0105] (4) Measurement of absorbance First, for preparing a calibration curve, a methylene blue solution without the adsorbent and a solution obtained by diluting this methylene blue solution without the adsorbent by a factor of 2 were prepared. Then, measure the absorbance of each solution to create a calibration curve. Next, measure the absorbance of the samples prepared in procedure (9), compare each absorbance with the calibration curve, determine the concentration of methylene blue remaining unadsorbed in the solution, and calculate the methylene blue adsorption amount (the amount of methylene blue per 1 g of the adsorbent (mg)) from this concentration of methylene blue. The results are shown in Table 2.

[0106]

Table 2

[0107] From the above results, when Na or K was used, the interlayer distance was small, and Na and K were present at the molecular adsorption sites, which inhibited adsorption. Therefore, it is considered that the adsorption performance was lower than that of Comparative Example 3 without an intercalator. On the other hand, in Examples 1, 2, and 3 using Mg, Ca, and Al as intercalators, respectively, an MXene structure with an interlayer distance suitable for the methylene blue molecular size was obtained, and it is considered that high adsorption performance was exhibited thereby.

[0108] This application claims priority based on Japanese Patent Applications No. 2021-003541 and No. 2021-028821. Japanese Patent Applications No. 2021-003541 and No. 2021-028821 are incorporated herein by reference.

Industrial Applicability

[0109] The adsorbent of the present invention can be used for any appropriate application, and can be preferably used, for example, as a separation membrane in artificial dialysis equipment.

Explanation of Signs

[0110] 1a, 1b Layer body (M m X n Layer) 3a, 5a, 3b, 5b Modification or termination T 7a, 7b MXene layer 10a, 10b MXene particles (particles of layered material) 20 Titanium atoms 21 Oxygen atoms 40 Hemodialysis equipment 41 Blood inlet 42 Blood outlet 43 Blood pump 44 Blood purification equipment 45 Separation membrane 46 Blood passage area of blood purification equipment 47 Dialysate passage area of blood purification equipment 48 Unused dialysate tank 49 Used dialysate tank 50 Dialysate pump

Claims

1. comprising particles of a layered material comprising one or more layers and one or more metal atoms selected from the group consisting of Al, Mg, and Ca, wherein said layer has the following formula: M m X n (wherein M is at least one metal of Groups 3, 4, 5, 6, 7, X is a carbon atom, a nitrogen atom, or a combination thereof, n is 1 or more and 4 or less, m is greater than n and 5 or less) and comprising a layer body represented by the formula and a modification or termination T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer body, an adsorbent in which M of the layer is bonded to at least one selected from the group consisting of a chlorine atom, a phosphorus atom, an iodine atom, and a sulfur atom.

2. The adsorbent according to claim 1, formed of particles of a layered material comprising a plurality of layers.

3. M and Cl of the layer - , PO 4 3- , I and SO 4 2- The adsorbent according to claim 1 or 2, wherein at least one selected from the group consisting of is bonded.

4. The adsorbent according to any one of claims 1 to 3, wherein the metal atom comprises one or more of Mg and Ca.

5. The adsorbent according to any one of claims 1 to 4, wherein the total content of one or more of Mg and Ca in the metal atom is 0.001% by mass or more and 1.5% by mass or less.

6. The adsorbent according to any one of claims 1 to 5, having an Li content of 0.0001% by mass or less (including 0% by mass).

7. The adsorbent according to any one of claims 1 to 6, further comprising one or more materials selected from ceramic, metal, and resin materials.

8. The adsorbent according to any one of claims 1 to 7, having a sheet-like form.

9. The adsorbent according to any one of claims 1 to 8, used for adsorbing a polar organic compound.

10. The adsorbent according to any one of claims 1 to 9, used for adsorbing a compound having one or more of a hydroxyl group and an amino group, and ammonia.

11. comprising particles of a layered material comprising one or more layers and one or more metal atoms selected from the group consisting of Al, Mg, and Ca, wherein said layer has the following formula: M m X n (wherein M is at least one metal of Groups 3, 4, 5, 6, 7, X is a carbon atom, a nitrogen atom, or a combination thereof, n is 1 or more and 4 or less, m is greater than n and 5 or less) A layer body represented by [formula], and a modification or termination T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer body, An adsorbent used for adsorbing uremic toxins, wherein M of the layer is bonded to at least one selected from the group consisting of a chlorine atom, a phosphorus atom, an iodine atom, and a sulfur atom.

12. Particles of a layered material including one or more layers, and one or more metal atoms selected from the group consisting of Al, Mg, and Ca, The layer is represented by the following formula: M m X n (In the formula, M is at least one metal of Groups 3, 4, 5, 6, and 7, X is a carbon atom, a nitrogen atom, or a combination thereof, n is 1 or more and 4 or less, m is greater than n and 5 or less) A layer body represented by [formula], and a modification or termination T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer body, An adsorbent used for adsorbing urea, wherein M of the layer is bonded to at least one selected from the group consisting of a chlorine atom, a phosphorus atom, an iodine atom, and a sulfur atom.

13. The adsorbent according to any one of claims 1 to 10, which is used for adsorbing a dye.

14. The adsorbent according to claim 13, wherein the dye is methylene blue.

15. An adsorption sheet using the adsorbent according to any one of claims 1 to 14.

16. A separation membrane using the adsorbent according to any one of claims 1 to 14.

17. Particles of a layered material including one or more layers, and one or more metal atoms selected from the group consisting of Al, Mg, and Ca, The layer is represented by the following formula: M m X n (In the formula, M is at least one metal of Groups 3, 4, 5, 6, and 7, X is a carbon atom, a nitrogen atom, or a combination thereof, n is 1 or more and 4 or less, m is greater than n and 5 or less) A layer body represented by [formula], and a modification or termination T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer body, An artificial dialysis device using an adsorbent, wherein M of the layer is bonded to at least one selected from the group consisting of a chlorine atom, a phosphorus atom, an iodine atom, and a sulfur atom.

18. (a) The following formula: M m AX n (In the formula, M is at least one metal of Groups 3, 4, 5, 6, and 7; X is a carbon atom, a nitrogen atom, or a combination thereof; A is at least one element of Groups 12, 13, 14, 15, and 16; n is 1 or more and 4 or less; m is greater than n and 5 or less). Preparing a precursor represented by the formula; (b) Performing an etching process of removing at least a part of A atoms from the precursor using an etching solution containing one or more of HCl, H 3 PO 4 , HI, and H 2 SO 4 ​ (c) Pickling the etched product obtained by the etching treatment; (d) Washing the pickled product obtained by the pickling with water to adjust the pH of the pickled product; (e) Performing a metal atom intercalation treatment including a step of mixing the water-washed product obtained by the water washing with a compound containing one or more metal atoms selected from the group consisting of Al, Mg, and Ca; and (f) Washing the metal atom intercalation product obtained by the metal atom intercalation treatment with water to obtain an adsorbent A method for producing an adsorbent, comprising the steps.

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