Ion adsorbent granulate and method for producing ion adsorbent granulate

Abstract

To provide an ion adsorbent granulate and a method for producing an ion adsorbent granulate enabling removal of heavy metal ions and allowing acquisition of treated water with high safety.SOLUTION: The ion adsorbent granulate comprises a crystalline material composed of a plurality of particles having an ion-exchange capacity and a layered crystal structure, and a binder containing an edible gelling agent and connecting the particles of the crystalline material to each other.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ion adsorbent granule and a method for producing the same, and in particular to an ion adsorbent granule and an ion adsorbent granule for removing heavy metal ions from a liquid using granules of layered double hydroxide crystals. [Background technology]

[0002] Conventional methods for treating heavy metal ions include adsorption, chemical precipitation, electrochemical methods, and ion exchange. Among these, adsorption is widely used because it is simple to operate and can easily treat wastewater containing heavy metal ions on a large scale. Types of adsorbents include, for example, carbons, synthetic polymers, MOFs, inorganic adsorbents, and natural polymers.

[0003] One example of an adsorbent is a filtering material made of a crystalline inorganic substance with a layered crystal structure produced by the flux method, intended to remove heavy metal ions contaminated in tap water (see Patent Document 1). The flux method is a technique in which a raw material substance and its solvent (flux) are heated, and then cooled or the solvent is evaporated to crystallize the substance. The crystalline inorganic substance used as the filtering material contains cationic components between the layers of the layered crystal structure that are ion-exchanged with heavy metal ions. Therefore, crystalline inorganic materials with a well-developed layered structure can exhibit high adsorption performance for heavy metal ions.

[0004] Layered double hydroxides (LDHs) are inorganic anion-exchangers, consisting of layered inorganic compounds with alternating layers of metal oxide (host layer) and anionic species and water molecules (guest layer). The anionic species in the guest layer can be exchanged with anionic species in solution while maintaining the layered structure, and are known to exhibit highly selective ion exchange properties by utilizing the interlayer (two-dimensional space).

[0005] For example, an adsorbent containing Mg-Al hydrotalcite has been devised as an adsorbent capable of simultaneously and selectively adsorbing nitrate ions, phosphorus, and arsenic from an aqueous solution (see Patent Document 2). Also, the ability of Mg-Fe hydrotalcite, represented by the following formula, to remove phosphate and nitrate ions has been disclosed (Non-Patent Document 1). Mg 0.666 Fe(III) 0.162 Al 0.172 (OH)2(Cl) 0.140 (CO3) 0.328H2O [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5551483 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-178682 [Non-patent literature]

[0007] [Non-Patent Document 1] "Removal Characteristics of Phosphate and Nitrate Ions with an Mg-Fe-Al-Cl Form Hydrotalcite" Tomoyuki Kuwabara, Hideo Kimura, Shunzi Sunayama, Ariumi Kawamoto, Hisamitsu Oshima and Toshio Sato;Journal of Society of Inorganic Materials,Japan 14,17-25(2007) Summary of the Invention [Problem to be solved by the invention]

[0008] In Patent Document 1, when a crystalline inorganic material is used as an adsorbent without modification, it is difficult to handle, as the adsorbent may be detached and washed away, and the original heavy metal ion adsorption capacity may not be fully exhibited. Furthermore, Patent Document 2 and Non-Patent Document 1 discuss phosphorus adsorption by Mg-Al-based layered peroxides and phosphate adsorption by Mg-Fe-based layered peroxides, but do not examine their adsorption properties for heavy metal ions. To solve this problem, a method of granulating the above-mentioned crystalline inorganic materials or LDHs is considered. However, when heavy metal ions are removed from wastewater using granules, binder components may be contained in the treated water after heavy metal ion removal. Therefore, if a typical binder resin is used for granulation, resin components will be contained in the treated water after heavy metal ion removal, which raises concerns about the use of the treated water as drinking water, etc., considering the impact on the human body, etc.

[0009] An object of the present invention is to provide an ion adsorbent granule and a method for producing the same, which are capable of removing heavy metal ions and obtaining highly safe treated water. [Means for solving the problem]

[0010] As a result of extensive research, the inventors have prepared granules comprising a crystalline material having ion exchange capacity and a layered crystalline structure, bound together by a binder containing an edible gelling agent. Using these granules as an ion adsorbent has been found to prevent the granules or primary particles from detaching from the granules, even when placed in a location where wastewater flows, improving handleability. Furthermore, the inventors have found that a portion of the surface of each primary particle constituting the granules can be maintained in an appropriately exposed state without being covered by the edible gelling agent, allowing the granules to fully exhibit their inherent heavy metal ion adsorption ability. Furthermore, because the binder binding the crystalline material contains an edible gelling agent, the treated water can be used as drinking water or tap water even if it contains components of the edible gelling agent after heavy metal ion removal, resulting in highly safe treated water. In particular, they found that by using sodium trititanate as the crystalline material and gelatin as the edible gelling agent, the gelatin improves the adhesion between sodium trititanate particles, resulting in superior adsorption of heavy metal ions. Furthermore, they found that the method can be easily manufactured using inexpensive and readily available materials, making it easy to obtain highly safe treated water even in areas where it is difficult to obtain materials or install equipment.

[0011] That is, the present invention provides the following configurations. [1] A crystalline material having ion exchange ability and composed of a plurality of particles having a layered crystal structure; a binder comprising an edible gelling agent and binding particles of the crystalline material together; An ion adsorbent granule comprising:

[0012] [2] The ion adsorbent granules according to [1], wherein the content of the binder is 0.5% by mass or more and 10% by mass or less when the total mass of the ion adsorbent granules is taken as 100% by mass.

[0013] [3] Median diameter D of the ion adsorbent granules 50 The ion adsorbent granules according to [1] or [2], wherein the average particle size is 10 μm or more and 3000 μm or less.

[0014] [4] The ion adsorbent granule according to [1] or [2], wherein the edible gelling agent contains gelatin.

[0015] [5] The ion adsorbent granule according to [1] or [2], wherein the crystalline material is represented by Na2Ti3O7 and contains layered crystals composed of a plurality of particles having a layered structure in which a plurality of plate-like crystals are stacked.

[0016] [6] The ion adsorbent granule according to [1] or [2], wherein the crystalline material contains layered double hydroxide crystals represented by the following formula (1) or formula (2) and composed of a plurality of particles having a layered structure in which a plurality of plate-like crystals are stacked: [Ni 2+ 1-x1 Fe 3+ x1 (OH)2]·[(Cl - ) X1 / 2 ] …(1) [Mg 2+ 1-x2 Fe 3+ x2 (OH)2]·[(Cl - ) X2 / 2 ] …(2) (where 0.25 <x1≦0.9、0.25<x2≦0.9)

[0017] [7] The ion adsorbent granule according to [6], wherein the range of x in the formula (1) and the formula (2) is 0.5≦x≦0.85.

[0018] [8] The ion adsorbent granules according to [1] or [2], which have a heavy metal ion removal rate of 98.5% or more.

[0019] [9] A step of preparing a crystalline material having ion exchange ability and composed of a plurality of particles having a layered crystalline structure; a step of mixing the crystalline material, an edible gelling agent, and water to bind a plurality of particles of the crystalline material together to form granules; A method for producing an ion adsorbent granule, comprising:

[0020]

[10] The method for producing the ion adsorbent granule according to [8], wherein the edible gelling agent contains gelatin.

[0021]

[11] The step of preparing the crystalline material is Step (A1) of mixing a titanium compound and a sodium organic acid salt to obtain a mixture; Step (A2) of firing the mixture at a temperature of 650°C or lower to obtain a layered crystal; The method for producing the ion adsorbent granule according to [9], which has the above steps.

[0022]

[12] The step of preparing the crystalline material is Step (B1) of preparing a raw material by adding a further sodium source substance to a mixture of a Ni source substance, an Fe source substance, and a Na source substance mixed based on the stoichiometric ratio of the precursor crystal; Heating the raw material at 600 to 1000°C for 1 hour or more to produce a precursor crystal composed of NaNi 1-x1 Fe x1 O2 crystal (0.25 < x1 ≤ 0.9) in step (B2); Ion substitution step (B3) of substituting the sodium ions of the precursor crystal with chloride ions to obtain a layered double hydroxide crystal; The method for producing the ion adsorbent granule according to [9], which has the above steps.

[0023]

[13] The step of preparing the crystalline material is Step (C1) of preparing a raw material by adding a further sodium source substance to a mixture of a Mg source substance, an Fe source substance, and a Na source substance mixed based on the stoichiometric ratio of the precursor crystal; Heating the raw material at 600°C to 1000°C for 1 hour or more to produce a precursor crystal composed of NaMg 1-x2 Fe x2 O2 crystal (0.25 < x2 ≤ 0.9) in step (C2); Ion substitution step (C3) of substituting the sodium ions of the precursor crystal with chloride ions to obtain a layered double hydroxide crystal; The method for producing the ion adsorbent granule according to [9], which has the above steps. [Effects of the Invention]

[0024] According to the present invention, it is possible to provide an ion adsorbent granule that can remove heavy metal ions and obtain highly safe treated water, and a method for producing the ion adsorbent granule. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an ion adsorbent granule according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing an example of the structure of the crystal material in FIG. [Figure 3] FIG. 3 is a flow chart showing an example of a method for producing a crystalline material that constitutes an ion adsorbent granule. [Figure 4] 4(a) and 4(b) are schematic diagrams for explaining each step of the method for producing the crystal material of FIG. [Figure 5] FIG. 5 is a graph showing the results of measuring the diffraction intensity of the ion adsorbent granules obtained in Examples 1 and 2 by powder X-ray diffraction (XRD). [Figure 6] 6(A) and 6(B) are electron microscope images showing the structure of the ion adsorbent granules obtained in Example 1. [Figure 7] FIG. 7 is an electron microscope image showing the structure of the ion adsorbent granules obtained in Example 1. [Figure 8] 8(A) and 8(B) are electron microscope images showing the structure of the ion adsorbent granules obtained in Example 1. [Figure 9] FIG. 9 is an electron microscope image showing the structure of the ion adsorbent granules obtained in Example 1. [Figure 10] FIG. 10 is a graph showing the measurement results of the particle size distribution of the ion adsorbent granules obtained in Example 1. [Figure 11] FIG. 11 is a graph showing the measurement results of the particle size distribution of the ion adsorbent granules obtained in Example 2. [Figure 12]12(A) and 12(B) are electron microscope images showing the structure of the ion adsorbent granules obtained in Example 3. [Figure 13] FIG. 13 is an electron microscope image showing the structure of the ion adsorbent granules obtained in Example 3. [Figure 14] FIG. 14 is a graph showing the metal ion adsorption capacity of the ion adsorbent granules obtained in Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the drawings used in the following description may show characteristic portions enlarged for the sake of clarity. Therefore, the dimensional ratios of each component may differ from the actual figures. Furthermore, the present invention is not limited to specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. For example, characteristic configurations of different embodiments may be combined.

[0027] <Ion adsorbent granules> As shown in FIG. 1, an ion adsorbent granule 1 according to an embodiment of the present invention comprises a crystalline material 10 having ion exchange capacity and composed of a plurality of particles 10A having a layered crystalline structure, and a binder 20 containing an edible gelling agent and connecting the particles of the crystalline material together.

[0028] Median diameter D of ion adsorbent granules 50 is not particularly limited, but is preferably 10 μm or more and 3000 μm or less, more preferably 10 μm or more and 2000 μm or less, even more preferably 10 μm or more and 500 μm or less, and particularly preferably 50 μm or more and 500 μm or less. 50 When the value of is within the above range, the heavy metal ion adsorption capacity can be further increased.

[0029] In this specification, the median diameter D of the ion adsorbent granules50 can be measured by the following wet method.

[0030] As a wet measurement method, a measurement method using a laser diffraction scattering method can be mentioned. Specifically, first, 2 g of powdered filtering material is added little by little directly to 50 ml of 0.2 mass % aqueous sodium hexametaphosphate solution while monitoring the absorbance, to obtain a dispersion liquid in which sodium trititanate is dispersed.

[0031] Next, the particle size distribution of the obtained dispersion is measured using a laser diffraction particle size distribution analyzer, and a volume-based cumulative particle size distribution curve is obtained. In the obtained cumulative particle size distribution curve, the particle diameter value at 50% accumulation from the fine particle side is the median diameter D 50 (μm). As the laser diffraction particle size distribution analyzer, for example, a particle size distribution analyzer SALD-7100 manufactured by Shimadzu Corporation can be used.

[0032] [Crystalline materials] The crystalline material is not particularly limited as long as it has ion exchange capacity and a layered crystalline structure. For example, it may contain layered crystals represented by Na2Ti3O7, which are composed of a plurality of particles having a layered structure in which a plurality of plate-like crystals are stacked. The crystalline material represented by Na2Ti3O7 may be in powder or granular form. The crystalline material represented by Na2Ti3O7 is not limited in its use, but is typically used as a heavy metal ion adsorbent. Na2Ti3O7 (sodium trititanate) contains sodium ions as cations. Sodium ions can be exchanged with heavy metal ions. Therefore, crystalline materials containing sodium trititanate can remove multiple types of heavy metal ions present in water.

[0033] When the total mass of the crystal material is taken as 100 mass%, the content of sodium trititanate is preferably 50 mass% or more, more preferably 70 mass% or more, and even more preferably 90 mass% or more. The upper limit is not particularly limited, and examples include 100 mass% or less, 99 mass% or less, and 98 mass% or less.

[0034] The upper and lower limits can be arbitrarily combined. Examples of combinations include a sodium trititanate content of 50% by mass to 100% by mass, 70% by mass to 99% by mass, and 90% by mass to 98% by mass, where the total mass of the crystal material is taken as 100% by mass.

[0035] The crystalline material may contain, in addition to sodium trititanate, an ion-exchangeable titanate compound, for example.

[0036] The crystalline material may contain or consist of sodium trititanate.

[0037] The crystalline material has a BET specific surface area of ​​1.0 m 2 / g or more 20.0m 2 / g or less is preferable, and 2.0m 2 / g or more 18.0m 2 / g or less is more preferable, and 3.0m 2 / g or more 16.0m 2 / g or less is more preferable.

[0038] The BET specific surface area of ​​a crystalline material can be measured using a BET specific surface area analyzer. For example, a BELSORP (registered trademark)-miniX manufactured by Microtrac-Bell can be used as the BET specific surface area analyzer. When measuring a powdered filtering material, it is preferable to dry it under vacuum at 150°C for 1 hour as a pretreatment.

[0039] The crystalline material has a median diameter D 50 The median diameter D of the crystalline material is preferably 1 nm or more and 30 nm or less, more preferably 2 nm or more and 28 nm or less, and even more preferably 3 nm or more and 26 nm or less. 50 The measurement method is the median diameter D 50 The measurement method is the same as that of

[0040] [binder] The binder of this embodiment contains an edible gelling agent. Examples of edible gelling agents include gelatin, starch, and agar. Gelatin is a fibrous protein called collagen. Starch is a polysaccharide formed by condensation polymerization of α-glucose. Agar is a polysaccharide derived from red algae. Of these, from the viewpoints of availability and binding strength, it is preferable that the edible gelling agent contains gelatin, and more preferably consists of gelatin.

[0041] The binder content, when the total mass of the heavy metal ion adsorbent granules is taken as 100% by mass, is not particularly limited, but is preferably 0.5% by mass to 10% by mass, more preferably 0.5% by mass to 7.0% by mass, and even more preferably 2.0% by mass to 7.0% by mass. By having the binder content within the above range, a good balance can be achieved between improving handleability by preventing particle detachment and maintaining the original heavy metal ion adsorption capacity.

[0042] The ion adsorbent granules of this embodiment can be used to remove heavy metal ions from a liquid, such as aluminum ions, cadmium ions, chromium ions, copper ions, iron ions, manganese ions, nickel ions, lead ions, and zinc ions.

[0043] (removal rate) When heavy metal ions contained in an aqueous solution are removed using the ion adsorbent granules of this embodiment, the removal rate of heavy metal ions calculated by the following formula is preferably 98.5% or more, more preferably 98.7% or more, and more preferably 99.0% or more.

[0044] Heavy metal ions present in water are qualitatively and quantitatively analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES) to measure the initial concentration (μg / L), which is the amount of heavy metal ions before removal, and the final concentration (μg / L), which is the amount of heavy metal ions after removal.The removal rate (%) is calculated from the initial and final concentration values ​​using the following formula. (Initial concentration - Final concentration) / Initial concentration x 100

[0045] [Other crystalline materials] FIG. 2 is a schematic diagram showing a modification of the crystal material 10 in FIG. As shown in Fig. 2, the crystalline material 10 contains layered double hydroxide crystals (hereinafter also referred to as layered double hydroxide, or LDHs crystals) represented by the following formula (1) and composed of a plurality of particles 10A having a layered structure in which a plurality of plate-like crystals 11, 11, ... are stacked. The other crystalline material represented by the following formula (1) is not limited in its use, but is typically used as an anion adsorbent, particularly a fluoride ion adsorbent. [Ni 2+ 1-x1 Fe 3+ x1 (OH)2]·[(Cl - ) X1 / 2 ] …(1) (where 0.25 <x1≦0.9) The layered double hydroxide crystals may be anhydrous or may be hydrated containing a small amount of water (H2O).

[0046] A layered space 12 is formed between adjacent plate crystals 11, 11, and a plurality of plate crystals 11, 11, . . . and a plurality of layered spaces 12, 12, .

[0047] The plate crystals 11 can also be referred to as thin plate crystals or sheet crystals. The plate crystals 11 have a thickness on the submicron order, and the layered spaces 12 also have spacing on the submicron order. The particles 10A are configured with a layered structure in which a plurality of these plate crystals 11, 11, ... are stacked in several to several tens of layers. The particle size or equivalent circle diameter in the width direction of the particles 10A is 0.1 μm to 300 μm, preferably 0.5 μm to 100 μm, and more preferably 1.0 μm to 50 μm. The particle size or equivalent circle diameter in the width direction of the plate crystals 11 is 0.1 μm to 300 μm, preferably 0.5 μm to 100 μm, and more preferably 1.0 μm to 50 μm.

[0048] Particle 10A is an anion-exchangeable inorganic ion exchanger, which can also be called a layered inorganic compound having a structure in which host layers (metal hydroxides) and guest layers (anion species and water molecules) are alternately stacked. Anion species in the guest layers can be exchanged with anion species in a solution while maintaining the layered structure, and therefore, the particle 10A exhibits highly selective ion exchange properties by utilizing the interlayer (also called two-dimensional space).

[0049] In the above formula (1), Ni 2+ is not limited to being completely substituted, but may be partially substituted. 3+ Similarly, the substitution is not limited to a complete substitution, but may be a partial substitution.

[0050] The range of x in the above formula (1) is preferably 0.5≦x1≦0.85, and more preferably 0.6≦x1≦0.8. In this case, Ni in the layered double hydroxide crystal 2+ Therefore, the amount of the Ni source material used during production can be reduced, and the production cost of the layered double hydroxide crystals can be further reduced.

[0051] The other crystalline material may also contain layered double hydroxide crystals represented by the following formula (2) and composed of a plurality of particles having a layered structure in which a plurality of plate-like crystals are stacked: The layered structure and particle morphology of the layered double hydroxide crystals (hereinafter also referred to as Mg-Fe-based layered double hydroxide crystals) in other embodiments are similar to those of the Ni-Fe-based layered double hydroxide crystals represented by the above formula (1), and therefore description thereof will be omitted. [Mg 2+ 1-x2 Fe 3+ x2 (OH)2]·[(Cl - ) X2 / 2 ] …(2) (where 0.25 <x2≦0.9)

[0052] The range of x in the above formula (2) is preferably 0.5≦x2≦0.85, and more preferably 0.6≦x2≦0.8. In this case, Mg in the layered double hydroxide crystal 2+Therefore, the amount of Mg source material used during production can be reduced, and the production cost of the layered double hydroxide crystals can be further reduced.

[0053] When the crystalline material is composed of a plurality of particles represented by the above formula (1) or (2) and having a layered structure in which a plurality of plate-like crystals are stacked, it has higher dispersibility than conventional materials, thereby achieving high ion exchange capacity. Therefore, the particles are less likely to aggregate even in an aqueous solution containing an edible gelling agent such as gelatin, and as a result, the ion exchange capacity of the layered double hydroxide crystals is increased, and sufficient ion exchange capacity can be achieved.

[0054] <Method of manufacturing ion adsorbent granules> The method for producing ion adsorbent granules according to this embodiment includes the steps of preparing a crystalline material having ion exchange capacity and composed of a plurality of particles having a layered crystalline structure, and mixing the crystalline material with an edible gelling agent and water to bond the plurality of particles of the crystalline material together to form granules.

[0055] [Preparation process] The step of preparing the crystal material can include, for example, any one of the following manufacturing steps (A) to (C).

[0056] (Manufacturing process (A)) A step (A1) of mixing a titanium compound with a sodium organic acid salt to obtain a mixture. A step (A2) of firing the mixture at a temperature of 650°C or less to obtain layered crystals.

[0057] (Step (A1) of Obtaining a Mixture) First, a titanium compound and a sodium organic acid salt are mixed to obtain a mixture. In this embodiment, it is preferable to mix a powder of the titanium compound and a powder of the sodium organic acid salt. In other words, it is preferable that the obtained mixture is a mixed powder.

[0058] The method for obtaining the mixture is not particularly limited as long as it is possible to stir and mix the titanium compound and the organic acid salt of sodium, and a commercially available stirring mixer may be used as appropriate.

[0059] The titanium compound used in this embodiment is preferably titanium dioxide.

[0060] In this embodiment, the sodium organic acid salt is a compound in which some or all of the carboxyl groups of an organic acid are substituted with sodium. In the case of an organic acid having two or more carboxyl groups in the molecule, all of the carboxyl groups may be substituted with sodium, or some of the carboxyl groups may be substituted with sodium. The organic acid is a material containing carbon.

[0061] The sodium organic acid salt used in this embodiment is preferably a sodium salt of one or more organic acids selected from the group consisting of formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, lactic acid, malic acid, tartaric acid, citric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, aconitic acid, pyruvic acid, oxaloacetic acid, benzoic acid, phthalic acid, and alginic acid.

[0062] In this embodiment, the sodium organic acid salt is more preferably one or more selected from the group consisting of trisodium citrate, sodium tartrate, sodium oxalate, and sodium acetate.

[0063] In this embodiment, the mixing ratio of the sodium organic acid salt and the titanium compound is preferably 2:3 in terms of the substance ratio of sodium to titanium.

[0064] In this embodiment, the mixture preferably comprises a titanium compound and a sodium organic acid salt.

[0065] In this embodiment, the mixture of the titanium compound and the sodium organic acid salt may further contain sodium carbonate.

[0066] In this embodiment, examples of combinations of titanium compounds and sodium organic acid salts are described below. Titanium dioxide and sodium acetate Titanium dioxide and trisodium citrate Titanium dioxide and sodium oxalate Titanium dioxide and sodium tartrate

[0067] In this embodiment, examples of combinations of a titanium compound with a sodium organic acid salt and sodium carbonate are described below. Titanium dioxide, sodium acetate, and sodium carbonate Titanium dioxide, trisodium citrate, and sodium carbonate Titanium dioxide, sodium oxalate, and sodium carbonate Titanium dioxide, sodium tartrate, and sodium carbonate

[0068] (Firing process (A2)) The resulting mixture is fired at a firing temperature of 650° C. or less. In this embodiment, the term "firing temperature" refers to the temperature set in the firing device. In the case of multiple firing steps, the term "firing temperature" refers to the highest temperature in each firing step.

[0069] The firing temperature is preferably 400° C. or higher and 650° C. or lower, and more preferably 500° C. or higher and 600° C. or lower. The method for producing a filtering material of the present embodiment uses the above mixture, and therefore can grow a layered crystal structure even when fired at a low temperature of 650° C. or lower.

[0070] The time for which the firing temperature is maintained is preferably from 5 hours to 15 hours, and more preferably from 7 hours to 12 hours.

[0071] The firing atmosphere may be an oxidizing gas atmosphere such as air or oxygen, or an inert gas atmosphere such as nitrogen, argon, or carbon dioxide, or a mixture of these gases may be used.

[0072] In this embodiment, an air atmosphere or an oxygen atmosphere is preferable. When using an air atmosphere, it is preferable to contain oxygen such that gas components other than oxygen become inert to the object to be fired at a temperature below the firing temperature.

[0073] The heating rate is preferably 0.5 °C / min or more and 50 °C / min or less, more preferably 0.5 °C / min or more and 10 °C / min or less, and even more preferably 1 °C / min or more and 5 °C / min or less.

[0074] When firing a mixture of a titanium compound and a sodium organic acid salt, it is preferable to raise the temperature at a heating rate of 1 °C / min or more and 5 °C / min or less, hold at a firing temperature of 400 °C or more and 650 °C or less for 7 hours or more and 12 hours or less.

[0075] When firing a mixture of a titanium compound, a sodium organic acid salt, and sodium carbonate, it is preferable to raise the temperature at a heating rate of 1 °C / min or more and 5 °C / min or less, hold at a firing temperature of 400 °C or more and 650 °C or less for 7 hours or more and 12 hours or less.

[0076] The firing apparatus used in this embodiment is not particularly limited as long as it can fire the obtained mixture at 650 °C or lower, and a commercially available electric furnace can be appropriately used. An example of an electric furnace that can be used in this embodiment is the electric furnace FO100 manufactured by Yamato Scientific Co., Ltd.

[0077] By the above manufacturing process (A), a crystal material represented by Na2Ti3O7 and containing layered crystals can be obtained.

[0078] (Manufacturing process (B)) · Step (B1) of preparing a raw material prepared by adding a further Na source material to a mixture of a Ni source material, an Fe source material, and a Na source material mixed based on the stoichiometric ratio of the precursor crystals · Heating the raw material at 600 to 1000 °C for 1 hour or more to produce precursor crystals composed of NaNi 1-x1 Fe x1 O2 crystals (0.25 < x1 ≤ 0.9) (Step (B2)) an ion substitution step (B3) in which sodium ions in the precursor crystals are substituted with chloride ions to obtain layered double hydroxide crystals;

[0079] Fig. 3 is a flow chart showing an example of a method for producing a crystalline material constituting an ion adsorbent granule. Fig. 4(a) and Fig. 4(b) are schematic diagrams for explaining each step of the production of the layered double hydroxide crystals shown in Fig. 3.

[0080] The method for producing layered double hydroxide crystals of this embodiment includes a raw material preparation step, a precursor crystal production step, a immersion step, and an ion substitution step. However, other treatment steps may be included before or after each of the steps in the production method of this embodiment.

[0081] (Step (B1) of preparing raw materials) First, a raw material is prepared by further adding a Na source material to a mixture of a Ni source material, an Fe source material, and a Na source material that are mixed based on the stoichiometric ratio of the precursor crystal described below (step S11).

[0082] Examples of Ni sources include NiO, Ni(OH)2, Ni(NO3)2, Ni(NO3)2·6H2O, NiCO3, NiSO4, NiSO4·6H2O, NiCl2NiCl2·6H2O, (HCOO)2Ni, (HCOO)2Ni·2H2O, C2O4Ni, C2O4Ni·2H2O, (CH3COO)2Ni, (CH3COO)2Ni·4H2O, Ni(CH3COCHCOCH3), Ni(CH3COCHCOCH3)·xH2O, NiCO3, NiCO3·xH2O, (NH4)2Ni(SO4)2, (NH4)2Ni(SO4)2·6H2O, and Ni.

[0083] Examples of Fe sources include Fe2O3, FeO, Fe(OH)2, Fe(OH)3, Fe(NO3)2, FeSO4, Fe2(SO4)3, FeCl2, FeCl3, FeC2O4, Fe2(C2O4)3, Fe(CH3COO)2, Fe2(CH3COO)3, Fe(CH3COCHCOCH3), Fe2(CH3COCHCOCH3)3, FeCO3, Fe2(CO3)3, (NH4)2Fe(SO4)2, (NH4)2Fe2(SO4)3, and hydrates thereof, and Fe.

[0084] Examples of Na source substances include NaNO3, Na2CO3, Na2SO4, Na2SO4·10H2O, Na2SO3, NaCl, CH3COONa, CH3COONa, CH3COONa·3H2O, C2O4Na2, C6H5Na3O7, C6H5Na3O7·2H2O, and NaHCO3. The content of the Na source substance in the raw material is preferably in excess of the content based on the stoichiometric ratio of the precursor crystal, and the excess amount relative to the stoichiometric Na source substance content (100 mol%) is more preferably 1 mol% to 50 mol%, even more preferably 3 mol% to 25 mol%, and particularly preferably 5 mol% to 15 mol%.

[0085] The Na source material in the raw material is composed of one or more of the above compounds. For example, the Na source material in the mixture may be composed of NaNO. In this case, the raw material is a mixture containing NiNO, which is mixed based on the stoichiometric ratio of the precursor crystal, and further containing NaNO. In addition, the Na source material in the above raw material may be composed of NaNO3 mixed based on the stoichiometric ratio of the precursor crystal and additionally added Na2CO3. In this case, a mixture obtained by further adding Na2CO3 to the mixture containing NO3 mixed based on the stoichiometric ratio of the precursor crystal is used as the raw material. The content of NaNO3 in the Na source material in the above raw material is preferably 1 mol% or more and 50 mol% or less, more preferably 3 mol% or more and 25 mol% or less, and still more preferably 5 mol% or more and 15 mol% or less. Also, the content of Na2CO3 in the Na source material in the above raw material is preferably 1 mol% or more and 10 mol% or less.

[0086] (Step (B2) of generating precursor crystals) Next, the raw material is heated at 600 to 1000 °C for 1 hour or more to generate precursor crystals composed of NaNi 1-x1 Fe x1 O2 crystals (0.25 < x1 ≦ 0.9) (Step S12, Fig. 3(a)). The method of crystal growth using a high-temperature molten salt in this way can be called the flux method, and in this embodiment, precursor crystals are generated by the flux method. Also, as the precursor crystals, preferably 0.5 < x1 ≦ 0.85, more preferably 0.6 < x1 ≦ 0.8, NaNi 1-x1 Fe x1 O2 crystals can be generated. Thereby, self-shaped and highly crystalline particles can be grown on the micro-order, and precursor crystals having a laminated structure in which a plurality of plate-like crystals are laminated can be obtained.

[0087] In this precursor crystal generation step, specifically, the above raw material can be heated, held, and cooled to generate the above precursor crystals. The heating conditions and cooling conditions in this precursor crystal generation step are, for example, a heating rate of 45 °C / h to 1600 °C / h, a holding temperature of 700 to 1000 °C, a holding time of 0.1 to 20 hours, a cooling rate of 0.1 to 60000 °C / h, a stop temperature of 500 °C or less, and a cooling temperature is, for example, room temperature. In this precursor crystal production process, for example, (1) heating from the start of heating to 700°C at a heating rate of 120°C / h or more and 600°C / h or less, heating from above 700°C to 800°C at a heating rate of 20°C / h or more and 180°C / h or less, then (2) holding at a temperature of 750°C or more and 900°C or less for a holding time of 0.5 hours or more and 12 hours or less, and then (3) cooling to 300°C at a cooling rate of 50°C / h or more and 300°C / h or less.

[0088] Then, for example, NaNi obtained in the precursor crystal production step 1-x1 Fe x1 The precursor crystals composed of O crystals are immersed in water. Because impurities contained in the water affect the composition of the final product, layered double hydroxide crystals, the water used in the immersion step is preferably pure water or ultrapure water. However, water containing a certain amount of impurities, such as tap water, may also be used as long as layered double hydroxide crystals exhibiting the desired ion exchange capacity are obtained.

[0089] When the precursor crystals are immersed in water, the solid-liquid ratio can be set to 25 mL / g or more and 1.0 L / g or less, and the stirring time can be set to 10 minutes or more and 40 hours or less. This immersion step increases the spacing between adjacent plate crystals while maintaining the shape of the plate crystals in the precursor crystals.

[0090] (Ion substitution step (B3)) Next, the sodium ions located between the layers of the obtained crystals are replaced with chloride ions (step S13, FIG. 4(b)). This replacement treatment is performed, for example, by immersing the obtained crystals in an aqueous solution of a strong acid. The strong acid is, for example, hydrochloric acid. When performing this replacement treatment, the solid-liquid ratio can be 50 mL / g or more and 1.00 L / g or less, the stirring time can be 10 hours or more and 40 hours or less, and the stirring temperature can be 20°C or more and 40°C or less, and preferably the solid-liquid ratio can be 100 mL / g or more and 1.00 L / g or less, the stirring time can be 10 hours or more and 40 hours or less, and the stirring temperature can be 20°C or more and 40°C or less.

[0091] By the above production step (B), a crystalline material containing layered double hydroxide crystals represented by the following formula (1) can be obtained. [Ni 2+ 1-x1 Fe 3+ x1 (OH)2]·[(Cl - ) X1 / 2 …(1) (where 0.25 < x1 ≦ 0.9, 0.25 < x2 ≦ 0.9)

[0092] (Manufacturing process (C)) · Step (C1) of preparing a raw material by adding a further Na source material to a mixture of a Mg source material, an Fe source material and a Na source material mixed based on the stoichiometric ratio of the precursor crystal · Heating the raw material at 600°C to 1000°C for 1 hour or more to produce a precursor crystal composed of NaMg 1-x2 Fe x2 O2 crystal (0.25 < x2 ≦ 0.9) · An ion substitution step (C3) of substituting the sodium ions of the precursor crystal with chloride ions to obtain a layered double hydroxide crystal

[0093] (Step (C1) of preparing a raw material First, a raw material prepared by adding a further Na source material to a mixture of a Mg source material, an Fe source material and a Na source material mixed based on the stoichiometric ratio of the precursor crystal described below is prepared.

[0094] Examples of the Mg source material include MgO, Mg(OH)2, Mg(NO3)2, MgSO4, MgCl2, MgC2O4, Mg(CH3COO)2, MgCO3 and their hydrates, and Mg.

[0095] Examples of Fe sources include Fe2O3, FeO, Fe(OH)2, Fe(OH)3, Fe(NO3)2, FeSO4, Fe2(SO4)3, FeCl2, FeCl3, FeC2O4, Fe2(C2O4)3, Fe(CH3COO)2, Fe2(CH3COO)3, Fe(CH3COCHCOCH3), Fe2(CH3COCHCOCH3)3, FeCO3, Fe2(CO3)3, (NH4)2Fe(SO4)2, (NH4)2Fe2(SO4)3, and hydrates thereof, and Fe.

[0096] Examples of Na source substances include NaNO3, Na2CO3, Na2SO4, Na2SO4·10H2O, Na2SO3, NaCl, CH3COONa, CH3COONa, CH3COONa·3H2O, C2O4Na2, C6H5Na3O7, C6H5Na3O7·2H2O, and NaHCO3. The content of the Na source substance in the raw material is preferably in excess of the content based on the stoichiometric ratio of the precursor crystal, and the excess amount relative to the stoichiometric Na source substance content (100 mol%) is more preferably 1 mol% to 50 mol%, even more preferably 3 mol% to 25 mol%, and particularly preferably 5 mol% to 15 mol%.

[0097] The Na source material in the raw material is composed of one or more of the above compounds. For example, the Na source material in the mixture may be composed of NaNO. In this case, the raw material is a mixture containing NiNO, which is mixed based on the stoichiometric ratio of the precursor crystal, and further containing NaNO. Further, the Na source material in the above raw materials may be composed of NaNO3 mixed based on the stoichiometric ratio of the precursor crystal and additionally added Na2CO3. In this case, a mixture obtained by further adding Na2CO3 to the mixture containing NO3 mixed based on the stoichiometric ratio of the precursor crystal is used as the raw material. The content of NaNO3 in the Na source material in the above raw materials is preferably 1 mol% or more and 50 mol% or less, more preferably 3 mol% or more and 25 mol% or less, and even more preferably 5 mol% or more and 15 mol% or less. Also, the content of Na2CO3 in the Na source material in the above raw materials is preferably 1 mol% or more and 10 mol% or less.

[0098] (Step (C2) of generating precursor crystals) Next, the above raw materials are heated at 600 to 1000 °C for 1 hour or more to generate precursor crystals composed of NaMg 1-x2 Fe x2 O2 crystals (0.25 < x2 ≤ 0.9). The method of crystal growth using a high-temperature molten salt like this can be called the flux method, and in this embodiment, precursor crystals are generated by the flux method. Also, as the precursor crystals, preferably 0.5 < x2 ≤ 0.85, more preferably 0.6 < x2 ≤ 0.8, NaMg 1-x2 Fe x2 O2 crystals can be generated. Thereby, self-shaped and highly crystalline particles can be grown on the micro-order, and precursor crystals having a laminated structure in which a plurality of plate-like crystals are laminated can be obtained.

[0099] In this precursor crystal generation step, specifically, the above raw materials can be heated, held, and cooled to generate the above precursor crystals. The heating conditions and cooling conditions in this precursor crystal generation step are, for example, a heating rate of 45 °C / h to 1600 °C / h, a holding temperature of 700 to 1000 °C, a holding time of 0.1 to 20 hours, a cooling rate of 0.1 to 60000 °C / h, a stop temperature of 500 °C or lower, and a cooling temperature is, for example, room temperature. In this precursor crystal production process, for example, (1) heating from the start of heating to 700°C at a heating rate of 120°C / h or more and 600°C / h or less, heating from above 700°C to 800°C at a heating rate of 20°C / h or more and 180°C / h or less, then (2) holding at a temperature of 750°C or more and 900°C or less for a holding time of 0.5 hours or more and 12 hours or less, and then (3) cooling to 300°C at a cooling rate of 50°C / h or more and 300°C / h or less.

[0100] Thereafter, for example, NaMg obtained in the precursor crystal production step 1-x2 Fe x2 The precursor crystals composed of O crystals are immersed in water. Because impurities contained in the water affect the composition of the final product, layered double hydroxide crystals, the water used in the immersion step is preferably pure water or ultrapure water. However, water containing a certain amount of impurities, such as tap water, may also be used as long as layered double hydroxide crystals exhibiting the desired ion exchange capacity are obtained.

[0101] When the precursor crystals are immersed in water, the solid-liquid ratio can be set to 25 mL / g or more and 1.0 L / g or less, and the stirring time can be set to 10 minutes or more and 40 hours or less. This immersion step increases the spacing between adjacent plate crystals while maintaining the shape of the plate crystals in the precursor crystals.

[0102] (Ion substitution step (C3)) Next, the sodium ions located between the layers of the obtained crystals are replaced with chloride ions. This replacement treatment can be carried out, for example, by immersing the obtained crystals in an aqueous solution of a strong acid. The strong acid is, for example, hydrochloric acid. When performing this replacement treatment, the solid-liquid ratio can be 50 mL / g or more and 1.00 L / g or less, the stirring time can be 10 hours or more and 40 hours or less, and the stirring temperature can be 20°C or more and 40°C or less, and preferably the solid-liquid ratio can be 100 mL / g or more and 1.00 L / g or less, the stirring time can be 10 hours or more and 40 hours or less, and the stirring temperature can be 20°C or more and 40°C or less.

[0103] By the above production step (C), a crystalline material containing layered double hydroxide crystals represented by the following formula (2) can be obtained. [Mg2+ 1-x2 Fe 3+ x2 (OH)2]·[(Cl - ) X2 / 2 ] …(2) (where 0.25 <x1≦0.9、0.25<x2≦0.9)

[0104] [Granulation process] In the granulation step of this embodiment, the crystalline material obtained in the preparation step, an edible gelling agent, and water are mixed together, and multiple particles of the crystalline material are bound together to form granules. For example, an edible gelling agent and water are mixed to prepare a mixed liquid (1), and then a crystalline material is added to the mixed liquid (1) so that the content of the edible gelling agent in the ion adsorbent granules falls within a predetermined range to prepare a mixed liquid (2). When the total mass of the mixed liquid (1) is taken as 100% by mass, the content of the edible gelling agent is not particularly limited, but is preferably 1.0 to 8.0% by mass, and more preferably 3.0 to 5.0% by mass. Thereafter, the water is removed from the mixed liquid (2) to prepare ion adsorbent granules. The method for removing the water is not particularly limited, and examples thereof include drying at room temperature and drying by heating. After removing the water, the ion adsorbent granules may be adjusted to a predetermined particle size by applying pressure to the mesh and rubbing the ion adsorbent granules against the mesh. Alternatively, primary particles of the crystalline material or ungranulated particles may be removed by sieving. By going through the above steps, the ion adsorbent granules of this embodiment are produced.

[0105] <Water treatment materials> This embodiment is a water treatment material containing the ion adsorbent granules of this embodiment and activated carbon. The ion adsorbent granules of this embodiment may be used in combination with activated carbon. By adjusting the mixing ratio of the ion adsorbent granules to the activated carbon, it is possible to adjust the balance between the size, replacement cycle, and cost of a water purifier cartridge, for example.

[0106] The activated carbon used in the water treatment material is preferably in the form of powder.

[0107] <Water purifier> This embodiment is a water purifier including the ion adsorbent granules of the present embodiment. The ion adsorbent granules of this embodiment can be suitably used as a filter medium for a water purifier.

[0108] The water purifier of this embodiment is a water purifier intended to remove impurities such as heavy metals contained in tap water. The water purifier can be installed in any of the well-known installation configurations, such as a direct-connection type attached to a water faucet, a freestanding type installed on a sink, or an under-sink type (built-in type) installed in a storage cabinet under the sink.

[0109] Alternatively, the pitcher-type water purifier may be a pitcher-type water purifier that can purify about 1 to 2 liters of raw water at a time for home use, etc., and can be stored as is in a refrigerator, etc. Examples of pitcher-type water purifiers include those having an outer container, an inner container that is detachably attached to the outer container and divides the outer container into upper and lower sections, and a water purification cartridge that is attached to the inner container.

[0110] The ion adsorbent granules of the present embodiment may be packed into a water purification cartridge that is detachably provided in a water purifier.

[0111] The ion adsorbent granules may also be used in water purification plants, sewage treatment plants, factories, and the like.

[0112] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0113] [Production of crystalline materials] (Production Example 1) 10.782 g of TiO2 and 7.383 g of sodium acetate were mixed to obtain powdery mixture 1. Mixture 1 was placed in a 30 mL alumina crucible with a lid. The mixture was fired using an electric furnace FO100 manufactured by Yamato Scientific Co., Ltd. The firing conditions were as follows: the temperature was raised from room temperature (about 20°C) at a rate of 5°C / min, and then the firing temperature was maintained at 600°C for 10 hours. Then, the electric furnace was turned off and the material was allowed to cool in the furnace to obtain a crystalline material.

[0114] [Production of ion adsorbent granules] Example 1 6.19 g of gelatin (manufactured by Jellice Co., Ltd., product name "Gelatin Powder Gelatin AU") was added to 85 g of water and the mixture was heated to dissolve the gelatin homogeneously. 200 g of the crystalline material obtained in Production Example 1 was mixed with the resulting gelatin aqueous solution and stirred in a mixer until granular. The mixture was then air-dried to remove moisture, and pressure was applied to rub the powder against a mesh to obtain a predetermined particle size, followed by sieving to obtain ion adsorbent granules. The gelatin content was 3.0% by mass when the total mass of the obtained ion adsorbent granules was taken as 100% by mass.

[0115] Example 2 Except for using 10.5 g of gelatin, an ion adsorbent granule was obtained in the same manner as in Example 1. The gelatin content was 5.0% by mass when the total mass of the obtained ion adsorbent granule was taken as 100% by mass.

[0116] Example 3 Except for using 1.41 g of gelatin, an ion adsorbent granule was obtained in the same manner as in Example 1. The gelatin content was 0.7% by mass when the total mass of the obtained ion adsorbent granule was taken as 100% by mass.

[0117] The ion adsorbent granules of Examples 1 to 3 obtained above were measured and evaluated by the following methods.

[0118] [Structure of crystalline material and ion adsorbent granules] The crystal structures of Production Example 1 and Examples 1 and 2 were identified by powder X-ray diffraction (XRD) using an XRD apparatus (Rigaku Corporation, "MiniFlexII").

[0119] [Appearance of ion adsorbent granules] The appearance of the ion adsorbent granules obtained in Examples 1 and 2 was confirmed by electron microscope images (manufactured by Rigaku Corporation, device name "JSM-7400F").

[0120] [Particle size distribution of ion adsorbent granules] The ion adsorbent granules obtained in Examples 1 and 2 were dispersed in distilled water, and the particle size distribution of the ion adsorbent granules was measured using a particle size distribution measuring device (Shimadzu Corporation, product name "SALD-7100").

[0121] First, the diffraction intensity of the crystalline material obtained in Production Example 1 was measured by powder X-ray diffraction (XRD), and the results are shown in Figure 6. From the X-ray diffraction pattern in Figure 6, it was confirmed that the crystalline material was sodium trititanate (Na2Ti3O7). The diffraction intensity of the ion adsorbent granules obtained in Examples 1 and 2 was measured by powder X-ray diffraction (XRD), and the results are shown in Figure 6. The X-ray diffraction patterns in Figure 6 confirmed that in both Examples 1 and 2, ion adsorbent granules were obtained in which the layered structure of the crystalline material was largely maintained.

[0122] The appearances of the ion adsorbent granules obtained in Example 1 are shown in Figures 6(a), 6(b), and 7, and the appearances of the ion adsorbent granules obtained in Example 1 are shown in Figures 8(a), 8(b), and 9. Furthermore, the measurement results of the particle size distribution of the ion adsorbent granules obtained in Example 1 are shown in Figure 10, and the measurement results of the particle size distribution of the ion adsorbent granules obtained in Example 2 are shown in Figure 11.

[0123] It was confirmed that in Example 1, ion adsorbent granules having the appearances shown in Figures 6(a), 6(b), and 7 were obtained. Furthermore, it was confirmed that the particle diameters of the ion adsorbent granules of Example 1 were distributed in the range of 100 µm to 300 µm, and that the relative particle amount q3 reached a maximum value in the particle diameter range of 200 µm to 250 µm, as shown in the graph of Figure 10. The median diameter D of the ion adsorbent granules of Example 1 was 50 The average particle size was 226.1 μm and the mean particle size was 226.8 μm.

[0124] It was confirmed that in Example 2, ion adsorbent granules were obtained having the appearances shown in Figures 8(a), 8(b), and 9. Furthermore, it was confirmed that the particle diameters of the ion adsorbent granules of Example 2 were distributed in the range of 100 µm to 300 µm, as shown in the graph of Figure 11, and that the relative particle amount q3 reached a maximum value in the particle diameter range of 200 µm to 250 µm. The median diameter D of the ion adsorbent granules of Example 2 50 The average particle size was 213.5 μm and the mean particle size was 213.0 μm.

[0125] In Example 3, it was confirmed that ion adsorbent granules having the appearances shown in Figs. 12(a), 12(b), and 13 were obtained.

[0126] [Evaluation of heavy metal ion adsorption capacity (1)] The heavy metal ion adsorption capacity was evaluated for the ion adsorbent granules of Examples 1 and 2. A multi-element mixed standard solution WV for ICP analysis (for drinking water testing) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used as the test solution containing heavy metal ions.

[0127] This standard solution is a nitric acid solution containing 11 elements: aluminum, boron, cadmium, chromium, copper, iron, molybdenum, manganese, nickel, lead, and zinc, each at a concentration of 100±5 mg / L.

[0128] This standard solution does not include non-metallic boron, molybdenum that may exist in the form of molybdate ions (anions), or sodium released from the filtering material as targets for removal in the test. In other words, the nine heavy metal ions to be removed were those other than non-metallic boron, molybdate ions (anions), and sodium released from the filtering material.

[0129] This standard solution was diluted 1000 times with water to adjust the concentration of each metal ion to 100±5 μg / L, and the resulting solution was used as the test solution. The initial pH of the test solution was 3.0 at room temperature, and the initial concentration was 100 ppb.

[0130] 70 mL of the prepared test liquid was placed in a 100 mL PFA bottle, and 70 mg of the ion adsorbent granules was added thereto, followed by shaking at room temperature (20°C) for 24 hours at 120 rpm.

[0131] After 24 hours, the suspension of the ion adsorbent granules and test solution was filtered, and the concentration of each heavy metal ion remaining in the aqueous solution was qualitatively and quantitatively analyzed by ICP-OES. This allowed us to measure the initial concentration (μg / L), which is the amount of heavy metal ions before removal, and the final concentration (μg / L), which is the amount of heavy metal ions after removal. The removal rate (%) was calculated from the initial and final concentrations using the following formula: The results are shown in Figure 14 and Table 1. (Initial concentration - Final concentration) / Initial concentration x 100

[0132] [Table 1]

[0133] 14 and Table 1, in Example 1, the removal rate of nine types of heavy metal ions was 98.82% or more, confirming that the heavy metal ions could be sufficiently removed. Also in Example 2, the removal rate of nine types of heavy metal ions was 98.56% or more, confirming that the heavy metal ions could be sufficiently removed.

[0134] [Evaluation of heavy metal ion adsorption capacity (2)] The heavy metal ion adsorption capacity of the ion adsorbent granules of Example 3 was evaluated by a water flow test. In the water flow test, the same test liquid as that used in the evaluation of the heavy metal ion adsorption capacity of Examples 1 and 2 was used. The column conditions and test conditions are shown below.

[0135] (Column conditions) Column: Biocolumn KF-18 Column size: 14mmD (inner diameter) x 30mmL Mass of ion adsorbent granules: 4.0g (Test conditions) Initial concentration: 100ppb multi-element mixed solution Initial pH: pH=3.01 Flow rate: 21.28mL / min Linear speed: 2.31mm / sec Contact time: 13.0sec Temperature: room temperature

[0136] In the same manner as above, the removal rate (%) was calculated from the initial concentration and final concentration values ​​using the following formula. The results are shown in Table 2.

[0137] [Table 2]

[0138] As shown in Table 2, in Example 3, the removal rate of nine types of heavy metal ions was 98.75% or more when the water flow rate was 1,809 mL, and even when the water flow rate increased, the removal rate was maintained at the same level as in the initial stage, confirming that excellent heavy metal ion adsorption could be maintained. [Explanation of symbols]

[0139] 1. Ion adsorbent granules 10 Crystalline Materials 10A particles 11 Plate-like crystals 12 Layered Space 20 binder

Claims

1. a crystalline material having ion exchange ability and composed of a plurality of particles having a layered crystal structure; a binder comprising an edible gelling agent and binding particles of the crystalline material together; An ion adsorbent granule comprising:

2. 2. The ion adsorbent granule according to claim 1, wherein the content of the binder is 0.5% by mass or more and 10% by mass or less, when the total mass of the ion adsorbent granule is taken as 100% by mass.

3. The median diameter D of the ion adsorbent granules ５０ The ion adsorbent granule according to claim 1 or 2, wherein the average particle size is 10 μm or more and 3000 μm or less.

4. The ion adsorbent granule according to claim 1 or 2, wherein the edible gelling agent comprises gelatin.

5. The crystalline material is Na ２ Ti ３ O ７ 3. The ion adsorbent granule according to claim 1, which contains layered crystals composed of a plurality of particles having a layered structure in which a plurality of plate-like crystals are stacked, and which are represented by the formula:

6. 3. The ion adsorbent granule according to claim 1 or 2, wherein the crystalline material contains layered double hydroxide crystals represented by the following formula (1) or (2) and composed of a plurality of particles having a layered structure in which a plurality of plate-like crystals are stacked: [Ni ２＋ １－ｘ１ Fe ３＋ ｘ１ (OH) ２ ]・[(Cl － ) Ｘ１／２ ] …(1) [Mg ２＋ １－ｘ２ Fe ３＋ ｘ２ (OH) ２ ]・[(Cl － ) Ｘ２／２ ] …(2) (where 0.25<x1≦0.9, 0.25<x2≦0.9)

7. The ion adsorbent granule according to claim 6, wherein the range of x in the formula (1) and the formula (2) is 0.5≦x≦0.

85.

8. 3. The ion adsorbent granule according to claim 1, wherein the removal rate of heavy metal ions is 98.5% or more.

9. A step of preparing a crystalline material having ion exchange ability and composed of a plurality of particles having a layered crystalline structure; a step of mixing the crystalline material, an edible gelling agent, and water to bind a plurality of particles of the crystalline material together to form granules; A method for producing an ion adsorbent granule, comprising:

10. The method for producing ion adsorbent granules according to claim 8 , wherein the edible gelling agent comprises gelatin.

11. The step of preparing a crystalline material includes: A step (A1) of mixing a titanium compound and a sodium organic acid salt to obtain a mixture; A step (A2) of firing the mixture at a temperature of 650°C or less to obtain layered crystals; The method for producing an ion adsorbent granule according to claim 9, comprising:

12. The step of preparing a crystalline material includes: a step (B1) of preparing a raw material by further adding a Na source material to a mixture of a Ni source material, an Fe source material, and a Na source material that have been mixed based on the stoichiometric ratio of the precursor crystal; The raw material is heated at 600 to 1000°C for 1 hour or more to form NaNi １－ｘ１ Fe ｘ１ O ２ A step (B2) of producing a precursor crystal composed of a crystal (0.25<x1≦0.9); an ion substitution step (B3) of substituting sodium ions of the precursor crystals with chloride ions to obtain layered double hydroxide crystals; The method for producing an ion adsorbent granule according to claim 9, comprising:

13. The step of preparing a crystalline material includes: a step (C1) of preparing a raw material by further adding a Na source material to a mixture of an Mg source material, an Fe source material, and a Na source material that have been mixed based on the stoichiometric ratio of the precursor crystal; The raw material is heated at 600°C to 1000°C for 1 hour or more to obtain NaMg １－ｘ２ Fe ｘ２ O ２ A step (C2) of producing a precursor crystal composed of a crystal (0.25<x2≦0.9); an ion substitution step (C3) of substituting sodium ions of the precursor crystals with chloride ions to obtain layered double hydroxide crystals; The method for producing an ion adsorbent granule according to claim 9, comprising:

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