Powder and method for producing powder

Abstract

The present invention addresses the problem of providing powder that facilitates a separation operation or a recovery operation. Powder according to the present invention contains aluminosilicate granules, and the aluminosilicate granules contain nanotube-shaped particles and magnetic particles.

Description

Powder and method for producing powder

[0001] The present invention relates to a powder. More specifically, the present invention relates to a powder comprising aluminosilicate granules. The present invention also relates to a method for producing the powder.

[0002] Patent Document 1 discloses a powder containing granules formed by aggregation of halloysite containing halloysite nanotubes.

[0003] International Publication No. 2018 / 079556

[0004] When the powder described in Patent Document 1 is dispersed in a liquid and processed, a further process of recovering the powder may be performed after the process. For example, when the powder is used as an adsorbent for targeting components in a liquid, solid-liquid separation is required to recover the adsorbent (powder) that has adsorbed the components in the liquid. Furthermore, when the powder described in Patent Document 1 is mixed with other powders to form a mixed powder and then processed, a further process of recovering the powder from the mixed powder may be performed after the process. Therefore, an object of the present invention is to provide a powder that can be easily separated or recovered. Another object of the present invention is to provide a method for producing a powder.

[0005] As a result of extensive research to achieve the above-mentioned objective, the inventors discovered that the granules contained in the powder contain nanotube-shaped particles and magnetic particles, which facilitates separation or recovery operations, and thus completed the present invention.

[0006] That is, the present invention provides the following [1] to

[16] . [1] A powder containing aluminosilicate granules, wherein the aluminosilicate granules contain nanotube-shaped particles and magnetic particles. [2] The powder according to [1], wherein the magnetic particles are soft magnetic particles. [3] The powder according to [2], wherein the soft magnetic particles are soft ferrite particles. [4] The powder according to any one of [1] to [3], wherein the content of the magnetic particles is 3 to 30 mass% with respect to the total mass of the aluminosilicate granules. [5] The powder according to any one of [1] to [4], wherein the aluminosilicate granules have pores with a pore diameter of more than 8 nm and not more than 200 nm. [6] The powder according to [5], wherein the aluminosilicate granules have, as the pores, first pores derived from the tube pores of the nanotube-shaped particles and second pores different from the first pores. [7] The powder according to any one of [1] to [6], wherein the aluminosilicate granules have pores with a pore size of 8 nm or less. [8] The powder according to any one of [1] to [7], wherein the aluminosilicate granules have pores with a pore size of 8 nm or less and pores with a pore size of more than 8 nm and not more than 200 nm. [9] The powder according to any one of [1] to [8], wherein the aluminosilicate granules have pores with a pore size of more than 200 nm.

[10] The powder according to any one of [1] to [9], wherein the aluminosilicate granules have pores with a pore size of more than 8 nm and not more than 200 nm and pores with a pore size of more than 200 nm.

[11] The powder according to any one of [1] to

[10] , wherein the aluminosilicate granules have pores with a pore size of 8 nm or less, pores with a pore size of more than 8 nm and less than 200 nm, and pores with a pore size of more than 200 nm.

[12] The powder according to any one of [1] to

[11] , wherein the aluminosilicate granules have first pores derived from the nanotube particles and having a pore size of more than 8 nm and less than 200 nm, second pores different from the first pores and having a pore size of more than 8 nm and less than 200 nm, and third pores with a pore size of 8 nm or less.

[13] The powder according to any one of [1] to

[12] , wherein the nanotube particles are nanotube aluminosilicate particles.

[14] The powder according to

[13] , wherein the nanotube particles comprise one or more types of particles selected from the group consisting of halloysite nanotube particles, metahalloysite nanotube particles, and modified halloysite nanotube particles.

[15] The powder according to any one of [1] to

[14] , wherein the aluminosilicate granules have an average particle size of 0.5 to 200 μm.

[16] A method for producing the powder according to any one of [1] to

[15] , comprising a step of preparing the powder from a slurry containing nanotube particles and magnetic particles.

[0007] According to the present invention, it is possible to provide a powder that can be easily separated or recovered, and a method for producing the powder.

[0008] 1 is an X-ray diffraction chart of the powder of an example. FIG. 2 is an SEM image of granules contained in powder 2 of an example. FIG. 3 is a pore size distribution chart of the powder of an example and a powder of a comparative example. FIG. 4 is a graph showing the progress of the amount of methylene blue adsorbed by the powder of an example. FIG. 5 is an X-ray diffraction chart of the powder of an example. FIG. 6 is an X-ray diffraction chart of the powder of an example. FIG. 7 is a result of pore size distribution analysis of the powder of an example by the BJH method. FIG. 8 is a result of pore size distribution analysis of the powder of an example by the BJH method.

[0009] Hereinafter, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0010] [Powder] The powder of the present invention is a powder containing aluminosilicate granules, the aluminosilicate granules containing nanotube particles and magnetic particles. The aluminosilicate granules containing magnetic particles are subjected to a force corresponding to the magnetic field in a magnetic field, and therefore, the granules dispersed in a liquid can be easily recovered. That is, for example, the aluminosilicate granules dispersed in a liquid are attracted to a magnet, facilitating solid-liquid separation. Furthermore, the aluminosilicate granules containing magnetic particles are attracted to a magnet even when mixed with other powders to form a mixed powder, and therefore, recovery or separation operations are easy.

[0011] The content of the aluminosilicate granules is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on the total mass of the powder of the present invention. The upper limit of the content of the aluminosilicate granules in the powder of the present invention is not particularly limited, and may be 100% by mass based on the total mass of the powder. That is, the powder of the present invention may consist of aluminosilicate granules.

[0012] In the aluminosilicate granules contained in the powder of the present invention, Al ２ O ３ SiO content ２ The molar ratio of the content of (hereinafter simply referred to as "SiO ２ / Al ２ O ３ " is also referred to as ".) is not particularly limited, but is preferably 1.8 or more. ２ / Al ２ O ３ is preferably 2.1 or more, may be 3.0 or more, or may be 5.0 or more. ２ / Al ２ O ３ The upper limit of is not particularly limited, and may be, for example, 10,000 or less and 1,000 or less, preferably 500 or less, more preferably 300 or less, and even more preferably 200 or less. ２ / Al ２ O ３ is determined by X-ray fluorescence (XRF) analysis. Specifically, analysis is performed by XRF under the following conditions, and SiO ２ / Al ２ O ３ The equipment used: ZSX Primus IV (Rigaku Corporation) Pretreatment method: Li ２ B ４ O ７ Glass bead method using fluxes and quantitative method: Refractory Technology Association's standard sample for X-ray fluorescence analysis (clay brick standard sample series) and calibration curve method using other reagents

[0013] The aluminosilicate granules contained in the powder of the present invention contain nanotube-shaped particles and magnetic particles. The aluminosilicate granules are not particularly limited as long as they contain nanotube-shaped particles and magnetic particles, and may contain other particles. The nanotube-shaped particles and magnetic particles are preferably contained as primary particles in the aluminosilicate granules. The aluminosilicate granules contained in the powder of the present invention contain nanotube-shaped particles and magnetic particles in each granule. In other words, the aluminosilicate granules contained in the powder of the present invention are composite granules containing nanotube-shaped particles and magnetic particles. The magnetic particles may be uniformly distributed or unevenly distributed in the aluminosilicate granules. When the magnetic particles are unevenly distributed in the aluminosilicate granules, the magnetic particles may be unevenly distributed in the center portion of the aluminosilicate granules or in the surface portion of the aluminosilicate granules. That is, when the magnetic particles are unevenly distributed in the aluminosilicate granules, the magnetic particles may be unevenly distributed as the core portion or as the shell portion. Here, the manner in which the magnetic particles are unevenly distributed can be adjusted appropriately depending on the application of the powder. For example, from the viewpoint of preventing deterioration of the magnetic particles or the liquid due to contact with the liquid, it is preferable that the magnetic particles are unevenly distributed in the core portion.

[0014] The content of nanotube particles in the aluminosilicate granules is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more, relative to the total mass of the aluminosilicate granules. The content of magnetic particles in the aluminosilicate granules is preferably 2% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and particularly preferably 8% by mass or more, relative to the total mass of the aluminosilicate granules, in order to facilitate separation and recovery operations. The content of magnetic particles in the aluminosilicate granules is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and particularly preferably 15% by mass or less, in order to increase the adsorption amount of the aluminosilicate granules, for example.

[0015] In this specification, the content of magnetic particles in the aluminosilicate granules is determined by the following formula: SiO ２ / Al ２ O ３ It can be measured using the same method as the measurement method of .

[0016] The nanotube particles and magnetic particles contained in the aluminosilicate granules will be described below.

[0017] <Nanotube particles> The nanotube particles are not particularly limited, but are preferably nanotube particles containing an alumina component and a silica component, and more preferably nanotube aluminosilicate particles. The nanotube particles preferably contain particles derived from halloysite nanotubes, which will be described later. The aluminosilicate granules may contain two or more types of nanotube particles.

[0018] Halloysite is Al ２ Si ２ O ５ (OH) ４ ・2H ２ O or Al ２ Si ２ O ５ (OH) ４ That is, SiO in halloysite ２ / Al ２ O ３ is generally 2.0. Halloysite generally exhibits a variety of shapes, such as tubular (hollow tubular), spherical, angular nodular, plate-like, and sheet-like. The inner diameter (diameter of the tube pore) of halloysite nanotube particles, which are tubular (hollow tubular) halloysite, is, for example, about 10 to 20 nm. The outer surface of the halloysite nanotube particles is mainly composed of silicate (SiO ２ ), and the inner surface is mainly made of alumina (Al ２ O ３ )

[0019] The term "particles derived from halloysite nanotubes" encompasses halloysite nanotube particles and particles obtained by subjecting halloysite nanotube particles to the treatment described below (hereinafter also referred to as "modified halloysite nanotube particles"). Examples of modified halloysite nanotube particles include metahalloysite nanotube particles obtained by calcining halloysite and acid-treated metahalloysite nanotube particles obtained by subjecting metahalloysite nanotube particles to acid treatment. The aluminosilicate granules may contain only halloysite nanotube particles, only modified halloysite nanotube particles, or both halloysite nanotube particles and modified halloysite nanotube particles. The aluminosilicate granules may also contain two or more types of modified halloysite nanotube particles.

[0020] The metahalloysite nanotube particles that can be contained in the above-mentioned aluminosilicate granules are Al ２ Si ２ O ５ (OH) ４ This refers to nanotube-shaped halloysite in which the OH of halloysite represented by the formula (I) is dehydrated to produce a low-crystalline state, and metahalloysite has traditionally been used generally or customarily as a term representing a variant of halloysite. Metahalloysite nanotube particles are obtained by firing halloysite nanotube particles at a predetermined temperature. The predetermined temperature is preferably 500°C or higher, and more preferably 600°C or higher. The upper limit of the predetermined temperature is preferably 925°C or lower, and more preferably 900°C or lower.

[0021] The acid-treated metahalloysite nanotube particles that can be contained in the above-mentioned aluminosilicate granules are obtained by subjecting metahalloysite nanotube particles to an acid treatment. The acid treatment refers to a treatment in which the metahalloysite nanotube particles are brought into contact with an acid treatment solution. The acid treatment reduces the Al content in the metahalloysite nanotube particles. ２ O ３The components are leached. The acid-treated metahalloysite nanotube particles often have third pores with a pore diameter of 8 nm or less, and have unique adsorption properties derived from these pores. The acid-treated metahalloysite nanotube particles may be those that have been subjected to a calcination treatment after the acid treatment. The acid-treated metahalloysite nanotube particles may also be obtained by performing the acid treatment in the state of aluminosilicate granules. Furthermore, after obtaining the acid-treated metahalloysite nanotube particles, a powder containing magnetic particles, which will be described in detail later, and the acid-treated metahalloysite nanotube particles may be obtained.

[0022] <Magnetic Particles> The magnetic particles are not particularly limited as long as they can be separated or recovered, but ferromagnetic particles are preferred. As the ferromagnetic particles, soft magnetic particles are preferred. Examples of magnetic particles (preferably soft magnetic particles) include metal magnetic particles and oxide magnetic particles, with oxide magnetic particles being preferred.

[0023] Examples of materials that constitute metal magnetic particles include metal materials containing one of the elements manganese, iron, cobalt, and nickel. Examples of materials that constitute oxide magnetic particles include ferrite, which is made primarily of iron oxide. That is, examples of oxide magnetic particles include ferrite particles.

[0024] The ferrite particles are not particularly limited, and ferrite particles with known crystal structures and compositions can be used. For example, the crystal structure of the ferrite particles may be any of spinel, magnetoplumbite, and garnet. Examples of components other than iron oxide contained in spinel ferrite particles include one or more elements selected from the group consisting of manganese, cobalt, nickel, copper, and zinc. Examples of components other than iron oxide contained in magnetoplumbite ferrite particles include one or more elements selected from the group consisting of barium, strontium, and lead. Examples of components other than iron oxide contained in garnet ferrite particles include one or more elements selected from the group consisting of rare earth elements.

[0025] As described above, the magnetic particles are preferably soft magnetic particles. Examples of soft magnetic particles include soft magnetic particles of simple metals such as iron, cobalt, and nickel, as well as soft magnetic particles of alloys containing these elements (Permalloy, Sendust (registered trademark)). The soft magnetic particles may be amorphous. Preferred examples of soft magnetic particles include soft ferrites (e.g., MnZn ferrite, CuZn ferrite, and NiZn ferrite).

[0026] The type of magnetic particles can be selected appropriately depending on the application environment of the powder of the present invention. For example, when the powder of the present invention is used as an adsorbent and a heat treatment is performed as a regeneration treatment, as described below, the magnetic particles preferably have heat resistance such that their physical properties do not change even when the heat treatment is performed. More specifically, when the heat treatment is performed in an oxygen-containing atmosphere, the magnetic particles are preferably oxide magnetic particles, and when the heat treatment is performed in a non-oxidizing atmosphere, the magnetic particles are preferably magnetic particles of a metal or alloy. In addition, it is preferable that the magnetic particles have the property of not being altered by the liquid to which the powder of the present invention is applied.

[0027] The shape of the magnetic particles is not particularly limited, and may be any of spherical, tabular, rod-like, polygonal columnar, etc. The particle size of the magnetic particles is not particularly limited, but is preferably 10 nm to 10 μm, more preferably 50 to 1000 nm.

[0028] The preferred properties of the powder of the present invention will be described below.

[0029] <Pores> The aluminosilicate granules contained in the powder of the present invention preferably have pores. The pores preferably have a pore size of more than 8 nm and not more than 200 nm, and more preferably more than 8 nm and not more than 100 nm. The presence or absence of pores can be confirmed by measuring an adsorption isotherm. Specifically, a nitrogen adsorption isotherm is obtained, and analyzed using the BJH (Barrett-Joyner-Halenda) method. A plot (log differential pore volume distribution) is created with pore size on the horizontal axis and differential pore volume on the vertical axis, thereby confirming the presence or absence of pores in the pore size range. The measurement conditions for obtaining the nitrogen adsorption isotherm will be described in detail in the Examples section below. The same applies to each measurement condition below.

[0030] Furthermore, the aluminosilicate granules contained in the powder of the present invention preferably have first pores derived from the pores of the nanotube-shaped particles and second pores different from the first pores. The second pores preferably correspond to the interparticle voids of the nanotube-shaped particles contained in the aluminosilicate granules. The pore sizes of the first pores and the second pores are preferably both in the range of more than 8 nm and not more than 200 nm, more preferably both in the range of more than 8 nm and not more than 100 nm, and even more preferably both in the range of 10 to 50 nm. The first pores are preferably in the range of 10 to 20 nm. It is also preferable that the log differential pore volume distribution analyzed by the BJH method shows two or more pore size peaks in the above range. The presence or absence of pores with a pore diameter of more than 8 nm and not more than 200 nm (more preferably, pores with a pore diameter of more than 8 nm and not more than 100 nm), and the presence or absence of first pores and second pores can also be confirmed by observing the aluminosilicate granules with an SEM. When the surface of the aluminosilicate granules is observed with an SEM, the presence of first pores derived from the tube structure of the nanotube particles can be confirmed, and when the cross section of the aluminosilicate granules is observed with an SEM, the presence of second pores can be confirmed. Examples of methods for observing the cross section of the aluminosilicate granules include a method of obtaining a sample by cutting with a focused ion beam (FIB) and then observing the sample.

[0031] Pores with a pore diameter of more than 8 nm and not more than 200 nm are in a region including mesopores, and are thought to have excellent mass transfer and adsorption properties, contributing to rapid reaction and adsorption.

[0032] The aluminosilicate granules contained in the powder of the present invention may have third pores having a pore size of 8 nm or less. The third pores having a pore size of 8 nm or less may be present together with the pores having a pore size of more than 8 nm and less than 200 nm. Furthermore, the aluminosilicate granules contained in the powder of the present invention may have the first pores having a pore size of more than 8 nm and less than 200 nm, the second pores having a pore size of more than 8 nm and less than 200 nm, and the third pores having a pore size of 8 nm or less. That is, the aluminosilicate granules contained in the powder of the present invention may have a hierarchical pore structure. The presence or absence of third pores having a pore size of 8 nm or less may be confirmed by performing a so-called t-plot analysis of a nitrogen adsorption isotherm to confirm the presence or absence of micropores less than 2 nm, or by fitting the nitrogen adsorption isotherm using the Grand Canonical Monte Carlo (GCMC) method to obtain a pore size distribution. The third pores having a pore size of 8 nm or less are, for example, possessed by acid-treated metahalloysite nanotube particles. For example, when aluminosilicate granules contain acid-treated metahalloysite nanotube particles, the aluminosilicate granules have third pores having a pore size of 8 nm or less. Note that general halloysite nanotube particles do not have third pores having a pore size of 8 nm or less. The pore size of the third pores having a pore size of 8 nm or less is preferably, for example, 1 to 5 nm. The third pores having a pore size of 8 nm or less may have multiple peaks in the range of 8 nm or less in the pore size distribution obtained by the above method.

[0033] The third pores with a pore diameter of 8 nm or less are nanospaces in a region close to the molecular size, and can therefore function as specific reaction fields and specific adsorption fields for molecules.

[0034] The aluminosilicate granules contained in the powder of the present invention may have pores with a pore diameter of greater than 200 nm. The pores with a pore diameter of greater than 200 nm may be present together with at least one of the pores with a pore diameter of greater than 8 nm and less than or equal to 200 nm and the third pores with a pore diameter of 8 nm or less. The presence or absence of the pores with a pore diameter of greater than 200 nm can be confirmed by observing the surface of the aluminosilicate granules with an SEM. In this specification, the size of pores with a pore diameter of greater than 200 nm refers to the diameter of the pores observed from the surface when the surface of the aluminosilicate granules is observed with an SEM. When the shape of the pores is not a perfect circle, the pore diameter of the pores with a pore diameter of greater than 200 nm is defined as the longest distance between two parallel lines tangent to the shape of the pore. The pore diameter of the pores with a pore diameter of greater than 200 nm is preferably 5,000 nm or less.

[0035] Pores with a diameter of more than 200 nm are believed to be effective in absorbing larger objects and promoting the adsorption and reaction of solid substances. For example, pores with a diameter of more than 200 nm can capture and react with (e.g., inactivate) dust, viruses, bacteria, pollen, and the like. In addition, pores with a diameter of more than 200 nm are believed to be effective in introducing highly viscous substances into the interior.

[0036] <Specific surface area> The specific surface area (BET specific surface area) of the powder of the present invention is 30 m ２ / g or more is preferable, and 50m ２ / g or more is more preferable. ２ The upper limit of the BET specific surface area is not particularly limited, but may be, for example, 1000 m ２ / g or less, and ２ / g or less. The BET specific surface area is 200 m ２ The BET specific surface area can be determined by applying the BET method to a nitrogen adsorption isotherm.

[0037] <Pore Volume> The total pore volume of the powder of the present invention is 0.20 cm ３ / g or more is preferable, and 0.23 cm ３ / g or more is more preferable. The total pore volume is 0.45 cm３ The upper limit of the total pore volume is not particularly limited, but may be, for example, 2.00 cm ３ / g or less, and 1.20 cm ３ / g or less. In addition, the total pore volume is 0.80 cm ３ The total pore volume is calculated from the adsorption amount at a relative pressure of 0.99 from the nitrogen adsorption isotherm using the following formula: Vp = V / 22414 × Mg / ρg Vp: total pore volume up to a relative pressure of (0.99) V: adsorption amount at a relative pressure of (0.99) 22414: volume of gas per mole Mg: adsorbate (N ２ ) molecular weight (28.013) ρg: adsorbate (N ２ ) density (0.808)

[0038] In addition, when the powder of the present invention has micropores (2 nm or less), the volume of the micropores is 0.01 cm ３ / g or more is preferable, and 0.02 cm ３ / g or more is more preferable, and 0.04 cm ３ / g or more is more preferable, and 0.08 cm ３ The upper limit of the volume of the micropores is not particularly limited, but is, for example, 0.5 cm ３ / g or less, and ３ / g or less in most cases.

[0039] <Other Components and Other Particles> In the powder of the present invention, the aluminosilicate granules may contain components other than the nanotube particles and magnetic particles. For example, the aluminosilicate granules may contain a catalyst component that promotes a desired reaction. The catalyst component may be supported as particles on the aluminosilicate granules or nanotube particles, or as clusters of single atoms or several atoms. The catalyst component may also be supported on the aluminosilicate granules and nanotube particles. The elements contained in the catalyst component are not particularly limited and can be selected depending on the desired reaction. Examples of elements contained in the catalyst component include Group 1 to Group 17 elements, and transition metal elements or rare earth elements are often included. The type of element contained in the catalyst component may be one type or two or more types. Note that the term "catalyst component" encompasses not only catalyst components that promote a desired reaction but also so-called co-catalysts that promote the desired reaction. Known catalyst components can be used. Furthermore, known methods can be appropriately applied to support the catalyst component.

[0040] In the powder of the present invention, the aluminosilicate granules may contain a medicinal component in addition to the nanotube particles and magnetic particles. The medicinal component is not particularly limited, and examples thereof include known deodorant components, antibacterial components, bactericidal components, and pharmaceutical components.

[0041] Furthermore, the aluminosilicate granules in the powder of the present invention may contain particles other than nanotube particles (other particles). The other particles are not particularly limited, but examples thereof include colorant particles, drug particles containing a drug component, and particles containing each of the above components.

[0042] <Characteristics of the Powder> The average particle size of the powder of the present invention is not particularly limited and may be appropriately selected depending on the application, but is, for example, 0.5 to 200 μm, preferably 1 to 100 μm. The powder of the present invention may be granulated before use. The size of the granulated powder is preferably 5 mm or less. The average particle size is measured using a laser diffraction / scattering particle size distribution analyzer (Microtrac MT3300EXII) manufactured by Microtrac-Bell.

[0043] The powder of the present invention also preferably has a breaking strength of 5.0 MPa or more. When the aluminosilicate granules contained in the powder of the present invention have the above-mentioned breaking strength, pores with a pore size of more than 8 nm and not more than 200 nm (e.g., first pores and second pores, particularly the second pores) are likely to be maintained. Therefore, when the aluminosilicate granules contained in the powder of the present invention have the above-mentioned breaking strength, they are less likely to be broken during handling, pretreatment (e.g., dispersion treatment), and composite treatment (e.g., kneading with resin), and the pores can be maintained. On the other hand, common porous materials such as silica gel, mesoporous silica, and activated carbon often have low particle breaking strength, and the particles may be broken during the above-mentioned operations, making it impossible to maintain the pore structure. The breaking strength is more preferably 6.0 MPa or more, and even more preferably 7.0 MPa or more. The upper limit of the breaking strength is not particularly limited, and is, for example, 60.0 MPa or less, preferably 50.0 MPa or less, and more preferably 45.0 MPa or less.

[0044] The breaking strength of the aluminosilicate granules is measured by a compression test using a micro-compression tester, and is the average of five test results. More specifically, first, the aluminosilicate granules contained in the powder of the present invention are used as a sample. A very small amount of this sample is scattered on the sample stage (lower pressure plate) of a micro-compression tester MCT-510 (manufactured by Shimadzu Corporation), and a compression test is performed on each sample particle to determine the breaking strength. Typically, the average of five test results (breaking strength) is used as the breaking strength of the powder. The breaking strength is calculated by measuring the diameters of each sample particle in the X and Y directions on the sample stage, and taking the average value as the particle size of each sample particle, using the following formula (1): (1) Cs = 2.48 × P / (πd２ In formula (1), Cs is the breaking strength (unit: MPa), P is the breaking test force (unit: N), and d is the diameter of the sample particle (unit: mm).

[0045] It is also preferable that the powder of the present invention has a water-impregnated breaking strength of 80% or more of the above-mentioned breaking strength when the aluminosilicate granules are immersed in pure water for 24 hours to impregnate them. The water-impregnated breaking strength may be the same value as the above-mentioned breaking strength, i.e., 100%. When the water-impregnated breaking strength is excellent, the pore structure is easily maintained even in applications involving contact with aqueous solutions, etc., and this is preferable. The water-impregnated breaking strength is measured in the same manner as the above-mentioned breaking strength measurement method, except that the sample is aluminosilicate granules that have been immersed in pure water for 24 hours to impregnate them.

[0046] The methylene blue adsorption amount of the powder of the present invention is preferably 10 mg / g or more, more preferably 15 mg / g or more, and even more preferably 20 mg / g or more. The methylene blue adsorption amount may be 40 mg / g or more. The upper limit of the methylene blue adsorption amount is not particularly limited, but may be, for example, 200 mg / g or less, and is often 100 mg / g or less. The methylene blue adsorption amount may be 50 mg / g or less. The above methylene blue adsorption amount indicates the amount of methylene blue adsorption per gram of the powder of the present invention. The amount of methylene blue adsorption per gram of powder is calculated from the concentration of the methylene blue solution before contact with the powder (pre-contact concentration), the concentration of the methylene blue solution obtained by stirring the powder and methylene blue solution overnight and then subjecting it to solid-liquid separation in a centrifuge (post-contact concentration), the amount of methylene blue solution used, and the amount of powder added. The methylene blue concentration is measured from the absorbance at 664.5 nm.

[0047] [Powder Applications] The powder of the present invention can be applied to various applications that utilize the pores derived from the nanotube particles. The powder of the present invention can be preferably used, for example, as an adsorbent. Furthermore, the powder of the present invention can be used in a wide variety of applications, not limited to adsorbents. Examples of applications include deodorizing materials, water purification materials, artificial enzymes, catalysts, catalyst carriers, sustained-release materials, antibacterial materials, disinfectants, precision polishing materials, magnetorheological fluids, cosmetics, coloring materials, foods, fermentation, and pharmaceuticals, but needless to say, the applications are not limited to these.

[0048] Furthermore, since the powder of the present invention is subjected to a force corresponding to the magnetic field when placed in a magnetic field (it is attracted to a magnet), it can also be used in applications that utilize this function. For example, since the powder of the present invention is easily separated into solid and liquid, it is particularly suitable for applications in which it is dispersed in a liquid for processing and the powder is recovered after processing. The powder of the present invention can also be preferably used in applications in which it is mixed with other powders to form a mixed powder for processing and the powder is recovered after processing. In addition, for example, components in a liquid phase or a gas phase can be adsorbed onto the powder, and the powder with the adsorbed components can be easily removed or transported, making it suitable for applications in which adsorption removal or recovery operations are performed.

[0049] As described above, the powder of the present invention has pores and is also capable of being attracted to a magnet, and therefore can be used in a variety of applications.

[0050] Furthermore, when the powder of the present invention is used as a heterogeneous catalyst, a solid acid catalyst, or a support for a catalyst component, reactants are easily diffused, and high activity can be expected. When the powder of the present invention has the above-mentioned pores (e.g., one or more of the first pore, the second pore, and the third pore), particularly high activity can be expected. Here, by utilizing the property of the powder of the present invention that it is subjected to a force according to a magnetic field, when the reaction phase of a catalytic reaction is a liquid phase, it is possible to recover the catalyst (powder of the present invention) from the liquid phase without filtration separation, which is considered to be advantageous for application to industrial processes, etc. Furthermore, in catalytic reactions in a liquid or gas phase flow method, even when the powder of the present invention is used in combination with other powders in a packed bed, it can be said that the powder of the present invention can be easily recovered after the reaction, etc.

[0051] The powder of the present invention is also expected to be used as a drug delivery system (DDS). Specifically, the pore structure is expected to have the function of controlled release, which slowly releases a drug, and the targeting function can also be controlled by magnetism. The powder of the present invention is also suggested to be applicable to processing, etc. Specifically, if a drug is impregnated into aluminosilicate granules, the aluminosilicate granules are controlled to move to a predetermined position using a magnetic field, and the drug is then released, the drug can be selectively released at a predetermined position, and it is expected that the powder can be processed into a desired pattern shape.

[0052] Furthermore, when the powder of the present invention is used as an adsorbent, the powder of the present invention that has adsorbed the adsorbate may be subjected to a regeneration treatment and reused as an adsorbent. The regeneration treatment is not particularly limited as long as the adsorbate is removed from the powder, and can be appropriately selected depending on the type of adsorbate. Examples of the regeneration treatment include a heat treatment in which the powder is heated, and an extraction treatment in which the powder is brought into contact with a liquid in which the adsorbate is easily dissolved. The powder of the present invention is unlikely to lose its adsorption ability even after heat treatment, and can be regenerated by heating at a high temperature. The heat treatment is preferably performed at 300°C or higher, but may also be 500°C or higher, 600°C or higher, 800°C or higher, or 900°C or higher.

[0053] Furthermore, the above-mentioned regeneration treatment can be preferably applied when the powder of the present invention is used as a catalyst, etc. In the regeneration treatment, the powder of the present invention is easy to separate and recover.

[0054] [Method for producing powder] A method for producing a powder of the present invention (hereinafter, for convenience, also referred to as the "production method of the present invention") will be described. The production method of the present invention preferably comprises at least a step of preparing a slurry containing nanotube particles and magnetic particles (slurry preparation step), and a step of preparing a powder from the slurry (powder preparation step). This results in aluminosilicate granules composed of an aggregate of nanotube particles and magnetic particles. Below, a preferred embodiment of the production method of the present invention in an embodiment in which the nanotube particles include halloysite nanotube particles will be described.

[0055] <Slurry Preparation Step> (Raw Material (Halloysite)) As the halloysite that is the raw material used in the production method of the present invention (hereinafter also referred to as "raw material halloysite"), commercially available halloysite (halloysite nanotubes) can be used, and specifically, for example, halloysite manufactured by APPLIED MINERALS (product name: DRAGONITE-HP) can be suitably exemplified.

[0056] (Slurrying) First, a slurry is obtained in which the raw halloysite is dispersed in water. The method for dispersing the raw halloysite in water is not particularly limited, and conventionally known devices such as a high-speed mixer, a disperser, a bead mill, and a homomixer can be used. The solid content concentration of the slurry is not particularly limited, and is, for example, 30 to 50 mass%.

[0057] It is preferable to add a dispersant to the slurry because it is closely related to the accuracy of centrifugation described later. By adding a dispersant, a slurry with a higher concentration can be obtained, which also has the effect of improving productivity in drying using a spray dryer or the like described later.

[0058] The dispersant is preferably one that can produce a stable slurry with a small amount of use, and examples thereof include polymeric anionic surfactants (anionic polymer surfactants). Specific examples of anionic polymer surfactants include special polycarboxylic acid types such as Poise 520, 521, and 530 (all manufactured by Kao Corporation). Depending on the intended use, Poise 532A, Kaocera 2000, 2020, and 2110 (also manufactured by Kao Corporation), which do not contain metal ions such as sodium and potassium, can also be used. Furthermore, the anionic polymer surfactant is not limited to polycarboxylic acid types; acrylic acid types, sulfonic acid types, etc. can also be used.

[0059] The content of the dispersant is not particularly limited, but a suitable example is 0.5 to 3.0 mass% relative to the total solid content in the slurry. If the content of the dispersant is too low, the dispersion of halloysite and impurity particles in the slurry may be insufficient. On the other hand, if the content of the dispersant is too high, aggregation may occur or costs may increase. Furthermore, problems in subsequent processes (such as a decrease in the recovery rate of the dispersed phase during centrifugation, insufficient drying during spray drying, or insufficient solidification or burning during firing) may be more likely to occur.

[0060] (Removal of Coarse Particles) In order to increase the accuracy of the centrifugal separation described below, coarse particles in the slurry may be removed. For example, a sieve with openings of 25 to 100 μm, a wet cyclone, or the like may be used to remove the coarse particles. Alternatively, the coarse particles may be removed by allowing the slurry to settle naturally.

[0061] (Centrifugation) The obtained slurry is centrifuged to separate it into a lower sedimentation phase and an upper dispersed phase. The sedimentation phase contains a large amount of impurities such as fine sand, while the dispersed phase contains a large amount of halloysite nanotube particles. The solids concentration of the dispersed phase (slurry) is, for example, 10 to 30 mass%. The centrifugal force and processing time during centrifugation are, for example, 2000 to 3000 G and 3 to 30 minutes, respectively, but are not limited to these and can be appropriately set taking into account the dispersion state, application, cost, etc. A large centrifuge can also be used for mass production. By recovering the dispersed phase, halloysite nanotube particles can be purified and separated from raw halloysite containing impurities such as fine sand.

[0062] (Addition of magnetic particles) Magnetic particles are added to the recovered dispersed phase (slurry). The amount added is, for example, but not limited to, an amount such that the content of magnetic particles in the slurry after addition is 2 to 50 mass% relative to the total amount of halloysite nanotube particles and magnetic particles in the slurry. After addition, the magnetic particles are dispersed in the slurry. The method is not particularly limited, and for example, conventionally known devices such as a high-speed mixer, a disperser, a bead mill, and a homomixer can be used. The slurry obtained in the slurry preparation step can also be subjected to operations such as purification, classification, magnetic separation, and concentration, as necessary. The magnetic particles can be prepared in the preferred embodiment described above. Commercially available magnetic particles may also be used.

[0063] <Powder Preparation Step> The powder preparation step is a step of preparing powder from the slurry prepared in the slurry preparation step. The powder obtained in the powder preparation step may be further granulated by subjecting it to treatments such as rolling, stirring, and extrusion. This allows the size of the granules constituting the powder to be increased.

[0064] (Spray Drying) The powder preparation step includes, for example, a step of spray drying the slurry prepared in the slurry preparation step to obtain a powder.

[0065] To spray-dry the prepared slurry, a spray dryer is used, which sprays (atomises) the liquid raw material into fine droplets and dries them with hot air to instantly produce powder. Spray dryers are conventionally known, including those manufactured by Okawara Chemical Engineering Co., Ltd., Fujisaki Electric Co., Ltd., and Japan Chemical Engineering Co., Ltd. In a spray dryer, the particle size of the powder particles (granules) obtained by drying can be controlled by changing the size of the droplets obtained by spraying (atomising) the liquid raw material. The method for atomising the liquid raw material using a spray dryer is not particularly limited, and conventional methods such as a two-fluid nozzle method, a pressure nozzle method, a four-fluid nozzle method (twin-jet nozzle method), or a rotating disk method can be appropriately selected depending on the desired droplet size. The particle size of the powder particles (granules) obtained by drying varies depending on the concentration and / or processing amount of the slurry. Therefore, to obtain the desired particle size, the state of the slurry must be appropriately selected in addition to the atomisation method. The contact method between the hot air and the sprayed droplets can be appropriately selected from the following types: a general parallel flow type in which the hot air and the sprayed droplets both flow downward; a counter flow type in which the hot air flows upward in a countercurrent to the downward flow of the sprayed droplets; and a parallel counter flow type in which the sprayed droplets flow upward and the hot air flows downward.

[0066] Spray drying applies heat instantaneously, so the powder itself does not easily become hot. Spray drying dries the slurry to directly obtain powder, eliminating the need for processes such as filtration, drying, and pulverization, and reducing contamination that can occur during these steps.

[0067] The method for obtaining powder by the spray drying process has been described above. However, as mentioned above, the method for obtaining powder is not particularly limited, and may be, for example, a method in which the above-mentioned slurry is subjected to medium fluidized drying (fluidized bed drying with balls). In outline, medium fluidized drying involves, for example, first continuously supplying the material to be dried, that is, the slurry, to a flowing layer of ceramic balls with a diameter of 1 to 3 mm, so that the material adheres to the ball surfaces. The material to be dried is instantly dried by heat conduction from the heated balls and convection heat transfer from the fluidized hot air, and is then peeled off from the ball surfaces by collisions between the balls. In this way, powder (aluminosilicate granules) is obtained.

[0068] By adjusting the procedure and conditions for obtaining the powder, the particle size of the granules in the obtained powder can be adjusted.

[0069] <Firing Step> The method for producing halloysite powder of the present invention may further include a step of firing the powder obtained in the powder preparation step (firing step).

[0070] When a surfactant is used in the post-slurrying process, the surfactant may remain in the powder obtained by spray drying or the like, but the firing process in an air atmosphere has the effect of removing the surfactant. Furthermore, the firing process can improve the breaking strength of the aluminosilicate granules contained in the powder.

[0071] The firing temperature is preferably a temperature at which the tubular structure of halloysite or metahalloysite can be maintained. Specifically, the firing temperature is preferably 200°C or higher, more preferably 300°C or higher, and even more preferably 400°C or higher. On the other hand, the firing temperature is preferably 1000°C or lower, more preferably 900°C or lower, and even more preferably 800°C or lower. The firing time is preferably 0.5 hours or longer, more preferably 0.75 hours or longer. On the other hand, the firing time is preferably 10 hours or shorter, and more preferably 5 hours or shorter.

[0072] The firing atmosphere is not particularly limited, and may be, for example, air.

[0073] When the manufacturing method of the present invention does not include a calcination step, the powder obtained in the powder preparation step is the powder of the present invention. On the other hand, when the manufacturing method of the present invention includes a calcination step, the powder calcined in the calcination step is the powder of the present invention.

[0074] In the manufacturing method of the present invention, it is also preferable to mix particles of a material that will disappear in the firing step (template particles) as primary particles into the slurry used in the spray drying step. When a slurry containing template particles is subjected to the spray drying step, aluminosilicate granules containing template particles, nanotube-shaped particles, and magnetic particles are obtained. When a powder containing such aluminosilicate granules is subjected to the firing step and the acid treatment step, the template particles are removed, and pores corresponding to the shape of the template particles are generated. By adjusting the shape and amount of the template particles, the spray drying conditions, etc., it is possible to generate macropores of the desired shape. Template particles of a material that will disappear in the firing step are not particularly limited, but examples include resin particles and carbon particles.

[0075] Although the above description illustrates a method for producing the present invention by spray-drying a slurry containing halloysite nanotube particles and magnetic particles, the powder of the present invention may also be produced by methods other than the above. Other production methods include, for example, removing the solvent component from a slurry containing nanotube particles and magnetic particles by drying to obtain a molded body, and then crushing the molded body to an appropriate size to obtain the powder of the present invention. In the production method of the present invention, the halloysite nanotube particles may be at least one of metahalloysite nanotube particles obtained by a calcination treatment and acid-treated metahalloysite nanotube particles obtained by a calcination treatment and an acid treatment. In the production method of the present invention, the powder of the present invention obtained by, for example, the calcination step may be further acid-treated to obtain the powder of the present invention. The powder obtained by the acid treatment may also be further washed. The powder obtained by the acid treatment or the powder obtained by washing may also be further subjected to a calcination step to obtain the powder of the present invention. The powder obtained by acid-treating the powder of the present invention obtained by the calcination step often has third pores with a pore size of 8 nm or less, which is preferable.

[0076] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

[0077] Example 1 Powder 1, which corresponds to the powder of the present invention, was produced by the following procedure.

[0078] <Raw Material Halloysite> As the raw material halloysite, halloysite manufactured by APPLIED MINERALS (product name: DRAGONITE-HP) was prepared.

[0079] <Slurrying> The raw halloysite, water, and an anionic polymer surfactant (Poise 530A, manufactured by Kao Corporation) were placed in a high-speed mixer (Ultra Homo Mixer UHM-20 (20 liters), manufactured by Nippon Seiki Seisakusho Co., Ltd.), and treated at 10,000 rpm for 10 minutes to obtain a slurry (solids concentration: 40% by mass) in which the raw halloysite was dispersed in water. The content of the anionic polymer surfactant relative to the total solids content of the slurry was 2.0% by mass.

[0080] <Centrifugation> Using a centrifuge (Kubota Shoji Co., Ltd., High-Speed, Large-Capacity Refrigerated Centrifuge 7000), the slurry was centrifuged at a centrifugal force of 2500 G for 10 minutes to separate it into a precipitated phase and a dispersed phase, and the dispersed phase was recovered. The recovered dispersed phase (slurry) had a solids concentration of 24% by mass. The solids concentration was measured using a halogen heating moisture meter (Shinko Denshi Co., Ltd., MA-120) at a dry heat treatment temperature of 200°C.

[0081] <Addition of Magnetic Particles> Magnetic particles were added to the recovered dispersed phase (slurry), and the mixture was processed for 10 minutes at 10,000 rpm using a high-speed mixer (Ultra Homo Mixer UHM-20, manufactured by Nippon Seiki Seisakusho Co., Ltd.) to disperse the magnetic particles in the slurry. The added magnetic particles were NiCuZn ferrite particles (KNI-106, manufactured by JFE Chemical Corporation; hereinafter, also referred to as "NiCuZn particles"). The average particle size of the NiCuZn particles was measured using a laser diffraction / scattering particle size distribution analyzer (Microtrac MT3300EXII) manufactured by Microtrac-Bell. The result was that the average particle size of the NiCuZn particles was 3.7 μm. The amount of magnetic particles added is as shown in Table 1 below.

[0082] <Spray drying> Granules containing magnetic particles were obtained by spray drying the slurry to which the magnetic particles had been added using a spray dryer. The spray dryer used was an L-8i spray dryer manufactured by Okawara Kakoki Co., Ltd., and the slurry was supplied at a fixed rate using a pump to atomize (spray) the slurry. The spray drying conditions were as follows: Atomization method: Four-fluid nozzle method Spray air pressure: 0.20 MPa Water evaporation rate: 2.5 kg / h Inlet temperature: 190°C Outlet temperature: 80°C

[0083] <Firing step> The obtained granules were fired to obtain aluminosilicate granules containing magnetic particles and metahalloysite nanotube particles. Specifically, the obtained granules were fired in an air atmosphere using an electric furnace with a siliconite heating element. The firing conditions were a temperature rise rate of 4°C / min, and after reaching 900°C, the temperature was maintained at 900°C for 1 hour, followed by furnace cooling.

[0084] [Example 2] The powder of Example 2 (Powder 2) was obtained in the same manner as the powder of Example 1, except that in the procedure for obtaining the powder of Example 1 (Powder 1), the amount of magnetic particles added to the slurry was changed to the amount shown in Table 1 below.

[0085] Example 3 A powder of Example 3 (Powder 3) was obtained in the same manner as the powder of Example 1, except that in the procedure for obtaining the powder of Example 1 (Powder 1), the magnetic particles added to the slurry were changed to MnZn ferrite particles (LD-M, manufactured by JFE Chemical Corporation; hereinafter, also referred to as "MnZn particles") and the amount of magnetic particles added to the slurry was changed to the amount shown in Table 1 below. The average particle size of the MnZn particles was measured using a laser diffraction / scattering particle size distribution analyzer (Microtrac MT3300EXII) manufactured by Microtrac-Bell. The resulting average particle size of the MnZn particles was 9.7 μm.

[0086] Comparative Example 1 Powder 4 containing no magnetic particles was obtained in the same manner as in the procedure for obtaining Powder 1 described above, except that magnetic particles were not added to the slurry subjected to spray drying.

[0087]

[0088] [Evaluation of Powders] Powders 1 to 4 obtained by the above procedure were evaluated as follows.

[0089] <XRD> Figure 1 shows the X-ray diffraction charts of Powders 1 to 3. The sharp diffraction peaks in each chart are peaks attributable to the crystalline structure of NiCuZn particles or MnZn particles, and diffraction peaks corresponding to halloysite nanotube particles were hardly observed. This is thought to be because the calcination step caused the crystal water in the halloysite nanotube particles to be eliminated, causing the halloysite nanotube particles to become amorphous and change into metahalloysite nanotube particles.

[0090] <SEM Observation> Each powder was observed by SEM. The results of observing the granules contained in Powder 2 are shown below. Figure 2 is an SEM image of the granules of Powder 2. From the SEM image in Figure 2, it was confirmed that Powder 2 contains granules (aluminosilicate granules) formed by the aggregation of halloysite containing halloysite nanotube particles. It was also confirmed that the granule surfaces contained pores (first pores) derived from the tube pores of the halloysite nanotube particles and pores (second pores) larger in diameter than the tube pores of the halloysite nanotube particles. Furthermore, since the magnetic particles are hardly observed on the surface in the SEM image in Figure 2, it can be inferred that the magnetic particles are coated with halloysite nanotube particles. In other words, it can be inferred that the magnetic particles are present in large numbers in the core of the obtained aluminosilicate granules. Similar SEM images were also obtained for Powders 1 and 3.

[0091] <Nitrogen adsorption isotherm> In the present invention, nitrogen adsorption isotherms were obtained under the following conditions and procedures, and various analyses were performed. First, the powder was pretreated (vacuum degassing at 120°C for 8 hours), and then the nitrogen adsorption isotherm and desorption isotherm were measured using a constant volume method under the following conditions. The equilibrium waiting time is the waiting time after the adsorption equilibrium state is reached. Adsorption temperature: 77 K Cross-sectional area of ​​nitrogen: 0.162 nm ２ Saturated vapor pressure: measured Equilibrium waiting time: 500 seconds Pretreatment device: BELPREP-vacII (manufactured by Microtrac BEL) Measurement device: BELSORP-mini (manufactured by Microtrac BEL) Analysis software: BELMaster Version 6.4.0.0 (manufactured by Microtrac BEL)

[0092] BET specific surface area [m ２ / g] was determined by applying the BET method from the nitrogen adsorption isotherm as described above. The BET specific surface areas and total pore volumes of Powders 1 to 4 obtained by the above measurements and analyses are shown in Table 2 below. The total pore volume was calculated from the amount of adsorption at a relative pressure of 0.99 from the nitrogen adsorption isotherm as described above.

[0093] Furthermore, the nitrogen adsorption isotherms of Powders 1 to 4 were analyzed for pore size distribution by the BJH method. The results are shown in Figure 3. In each graph, the horizontal axis represents pore size [nm], and the vertical axis represents differential pore volume (dVp / dlogDp) [cm ３ / g]. In the graph of Figure 3, two or more pore size peaks were confirmed within the range of 10 nm or more (more than 8 nm and 100 nm or less). The peak observed near 20 nm corresponds to the first pores derived from the tube pores of the nanotube-shaped particles, and the peak observed near 50 nm corresponds to the second pores corresponding to the inter-particle voids of the nanotube-shaped particles.

[0094] <Average Particle Diameter> The average particle diameters of Powders 1 to 4 were measured by the method described above, and the results are shown in Table 2 below.

[0095]

[0096] Methylene Blue Adsorption Test and Solid-Liquid Separation Test First, a methylene blue solution for bacterial staining (Sigma-Aldrich, methylene blue concentration: 0.5% by mass in 100 mL) was diluted with pure water to prepare a 0.02% by mass methylene blue solution. Centrifuge tubes containing 50 mL of the prepared methylene blue solution and 0.75 g of each powder were placed in a tube rotator (MX-RL-Pro, AS ONE Corporation) and stirred at room temperature for 24 hours. After stirring, the contents of the centrifuge tubes were subjected to a centrifugal force of 3000 G for 15 minutes using a centrifuge (Kubota Shoji, High-Speed, Large-Capacity Refrigerated Centrifuge 7000). Visual observation of the separated contents revealed that the settled solids were blue, while the liquid was nearly colorless and transparent. Furthermore, when a methylene blue solution alone was subjected to centrifugal force under the same conditions as above, it was confirmed that the methylene blue solution exhibited a uniform blue color. Therefore, it is believed that methylene blue molecules were adsorbed onto each powder. In this case, the amount of methylene blue adsorbed per gram of each powder was estimated to be 13 mg / g.

[0097] Furthermore, the dispersion containing methylene blue-adsorbed Powder 1 was stirred at room temperature for 24 hours using the same procedure as above, and then transferred to a glass Petri dish. A commercially available neodymium magnet was placed at the bottom of the Petri dish, attracting the blue Powder 1, allowing separation into a colorless, transparent liquid phase and Powder 1. This confirms that Powder 1 (the powder of the present invention) is easily separated into solid and liquid after being dispersed in a liquid and processed. More specifically, it was confirmed that Powder 1, after being dispersed in a liquid and processed to adsorb the adsorbate, could be easily separated into solid and liquid by a simple operation using magnetic force, and that Powder 1 with the adsorbate adsorbed could be easily recovered. Powders 2 and 3 were also attracted to the magnet, similar to Powder 1, and were separated into a colorless, transparent liquid phase and Powder 2 or Powder 3. On the other hand, Powder 4 was not attracted to the magnet and solid-liquid separation was not possible.

[0098] <Repeated Adsorption Characteristics> Powder 1, which had adsorbed methylene blue, was recovered by solid-liquid separation and calcined at 900°C for 1 hour. The blue color of Powder 1 disappeared. This suggests that methylene blue was desorbed from Powder 1 by calcination. The regeneration treatment by heating was performed in this manner, and the regenerated Powder 1 was allowed to adsorb methylene blue again, and the adsorption amount was estimated. Furthermore, the regeneration treatment described above was further performed on the Powder 1 to which methylene blue had been adsorbed again. The change in the saturated adsorption amount of methylene blue for Powder 1 was measured when the above-described adsorption of methylene blue and the regeneration treatment were repeatedly performed. Similarly, the change in the saturated adsorption amount of methylene blue for Powder 2 and Powder 3 was measured. The results are shown in Figure 4. The saturated adsorption amount was determined by the method described above. Specifically, each powder was added to a 0.02 mass% methylene blue solution in an amount of 1 / 200 of the mass of the methylene blue aqueous solution, and the amount of methylene blue adsorbed per gram of powder was calculated from the concentration of the methylene blue solution before and after contact with the powder.

[0099] From the results shown in FIG. 4, it was confirmed that Powder 1, Powder 2 and Powder 3 (powders of the present invention) maintained the adsorption amount of methylene blue even after repeated regeneration treatment by heating.

[0100] [Example 4] Powder 1 obtained in Example 1 was subjected to an acid treatment according to the following procedure to obtain Powder 5. Hydrochloric acid (acid treatment solution) with the following concentration was used for the acid treatment. The acid treatment was performed by placing Powder 1 and the following acid treatment solution in a glass beaker and stirring with a PTFE stirring blade. The glass beaker was heated with a mantle heater, and the liquid temperature was controlled to the following temperature. After the acid treatment, solid-liquid separation was performed by suction filtration, and then a process of dispersing the powder in ion-exchanged water and a process of solid-liquid separation (washing process) were repeatedly performed using ion-exchanged water until the conductivity of the filtrate reached the following value. After the washing process, the powder was dried at 110°C to obtain a powder (Powder 5).

[0101] <Acid treatment conditions> Acid treatment solution: 2 mol / L hydrochloric acid Solution temperature: 60°C Time: 2 hours Ratio of mass of acid treatment solution to mass of calcined powder or uncalcined powder (powder / acid treatment solution): 25 Filtrate conductivity at the end of washing: 1 mS / m

[0102] [Example 5] A powder of Example 5 (powder 6) was obtained in the same manner as in Example 4, except that in the procedure for obtaining powder 5 of Example 4, the powder subjected to acid treatment was changed from the powder of Example 1 (powder 1) to the powder of Example 3 (powder 3).

[0103] Example 6 Powder 5 obtained by the above procedure was further calcined at 900° C. for 1 hour (post-calcination) to obtain powder (powder 7).

[0104] Example 7 Powder 5 obtained by the above procedure was further calcined at 900° C. for 1 hour (post-calcination) to obtain powder (powder 8).

[0105] [Evaluation of Powders] Powders 5 to 8 obtained by the above procedure were evaluated in the same manner as powders 1 to 4. The results will be described below.

[0106] First, Table 3 shows the saturated adsorption amount of methylene blue for powders before and after acid treatment. Note that the post-baking temperatures shown in the columns for Powder 5 and Powder 6 in Table 3 are the drying temperatures described above.

[0107]

[0108] The results shown in Table 3 indicate that Powders 5 to 8 obtained by acid treatment each adsorbed an increased amount of methylene blue compared to Powders 1 and 3, which were powders before the acid treatment. Furthermore, the results shown in Table 3 indicate that, when comparing the powders before the acid treatment (Powder 1 and Powder 3) with the powders after the acid treatment (Powder 5 and Powder 7, and Powder 6 and Powder 8), the BET specific surface area and total pore volume of the powders after the acid treatment were increased. Powders 5 to 8, which had adsorbed methylene blue and were dispersed in a dispersion liquid, were also attracted to a magnet, similar to Powder 1 and the like. Furthermore, it was confirmed that Powders 5 to 8 were attracted to a neodymium magnet even in a dry state.

[0109] Figures 5 and 6 show X-ray diffraction charts of Powders 5 and 6, respectively. Note that Figure 5 shows X-ray diffraction charts of Powders 1 and 5, and Figure 6 shows X-ray diffraction charts of Powders 3 and 6. As described above, the sharp diffraction peaks in the diffraction charts of Powders 1 and 3 are peaks attributable to the crystal structure of NiCuZn particles or MnZn particles. Sharp diffraction peaks are also observed in the diffraction charts of Powders 5 and 6 that were subjected to the acid treatment described above, and no change was observed even after the acid treatment.

[0110] 7 and 8 show the results of pore size distribution analysis using the BJH method. In acid-treated Powders 5 and 6, in addition to the first pores derived from the tube pores of the nanotube particles and the second pores corresponding to the interparticle voids of the nanotube particles, pores of 8 nm or less that were not observed in the powders before acid treatment (Powder 1 and Powder 3) were observed. Pores of 8 nm or less were also observed in Powder 7, which was obtained by calcining Powder 5 at 900°C, and Powder 8, which was obtained by calcining Powder 6 at 900°C. The formation of these pores is thought to contribute to the increase in the amount of methylene blue adsorbed.

[0111] Powders 5 and 6, which had been subjected to acid treatment, and Powders 7 and 8, which had been further fired at 900°C, were attracted to the neodymium magnet even in a dry state, and it is believed that, like Powders 5 and 6, Powders 7 and 8 also contain NiCuZn particles or MnZn particles, respectively, and that there is no change in the magnetic properties associated with these particles. In other words, even when fired at 900°C after acid treatment, the pore structure and magnetism are maintained, and therefore a regeneration process by heating can be applied.

[0112] From the above results, it was confirmed that even powders obtained by acid treatment of powders containing aluminosilicate granules composited with magnetic powder and nanotube particles are attracted to a magnet and easy to separate solid-liquid (separation operation). Furthermore, it was confirmed that the acid treatment generates pores of 8 nm or less, increasing the amount of methylene blue adsorbed. Therefore, powders 5 to 8 obtained by acid treatment are powders with high adsorption capacity and easy to separate solid-liquid (separation operation). It was also confirmed that they are attracted to a magnet even in a dry state, facilitating recovery. In other words, the powder of the present invention is a powder that is easy to separate and recover. Of course, as described above, the powder of the present invention may also be obtained using acid-treated metahalloysite nanotube particles obtained by prior calcination and acid treatment. The acid-treated metahalloysite nanotube particles often have pores of 8 nm or less, which is advantageous in terms of improved adsorption capacity.

Claims

1. A powder comprising aluminosilicate granules, wherein the aluminosilicate granules comprise nanotube particles and magnetic particles.

2. The powder of claim 1, wherein the magnetic particles are soft magnetic particles.

3. The powder of claim 2, wherein the soft magnetic particles are soft ferrite particles.

4. The powder according to any one of claims 1 to 3, wherein the content of the magnetic particles is 2 to 50 mass % based on the total mass of the aluminosilicate granules.

5. The powder according to any one of claims 1 to 4, wherein the aluminosilicate granules have pores with diameters of more than 8 nm and not more than 200 nm.

6. The powder according to claim 5, wherein the aluminosilicate granules have, as the pores, first pores derived from the tube pores of the nanotube-like particles and second pores different from the first pores.

7. The powder according to any one of claims 1 to 6, wherein the aluminosilicate granules have pores with a pore size of 8 nm or less.

8. The powder according to any one of claims 1 to 7, wherein the aluminosilicate granules have pores with a pore size of 8 nm or less and pores with a pore size of more than 8 nm but not more than 200 nm.

9. The powder according to any one of claims 1 to 8, wherein the aluminosilicate granules have pores with a pore size of more than 200 nm.

10. The powder according to any one of claims 1 to 9, wherein the aluminosilicate granules have pores with a pore size of more than 8 nm and not more than 200 nm and pores with a pore size of more than 200 nm.

11. The powder according to any one of claims 1 to 10, wherein the aluminosilicate granules have pores with a pore size of 8 nm or less, pores with a pore size of more than 8 nm and less than 200 nm, and pores with a pore size of more than 200 nm.

12. The powder according to any one of claims 1 to 11, wherein the aluminosilicate granules have first pores derived from the nanotube particles and having a pore size of more than 8 nm and not more than 200 nm, second pores different from the first pores and having a pore size of more than 8 nm and not more than 200 nm, and third pores having a pore size of not more than 8 nm.

13. The powder according to any one of claims 1 to 12, wherein the nanotubular particles are nanotubular aluminosilicate particles.

14. The powder of claim 13, wherein the nanotube particles comprise particles derived from halloysite nanotubes.

15. The powder according to any one of claims 1 to 14, wherein the aluminosilicate granules have an average particle size of 0.5 to 200 µm.

16. A method for producing the powder of any one of claims 1 to 15, comprising the step of preparing the powder from a slurry containing nanotube particles and magnetic particles.

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