JP2023125494A - Potassium adsorbent for biological fluids and potassium adsorbent for dialysate - Google Patents

Abstract

To provide a potassium adsorbent suitable for at least one of biological fluid and dialysate, which exhibits high adsorptivity to potassium, even with the presence of sodium, calcium and magnesium, such as in biological fluid or dialysate, and a method for producing the same; a potassium adsorbing method using the potassium adsorbent; and a potassium adsorbing system using the same.SOLUTION: Provided herein is a potassium adsorbent for at least one of biological fluid and dialysate, with the molar ratio of silica to alumina (SiO2/Al2O3 ratio) of 3 or more and 100 or less, and the potassium adsorbent containing a zeolite having at least an oxygen eight-membered-ring.SELECTED DRAWING: None

Description

The present disclosure relates to a potassium adsorbent for biological fluids and a potassium adsorbent for dialysate.

Removal of excess potassium from biological fluids, including blood products, and regulation of potassium levels are important to reduce the risk of adverse effects during blood transfusions.

In order to remove potassium from blood and blood products, it is known to use polymer beads containing porous sulfonate functional groups as adsorbents (US Pat. No. 5,001,302).

In addition, conventional dialysis processes require the preparation of large amounts of purified water (ultrapure water) in order to prepare dialysate that is used once and then immediately discarded. Therefore, there is a need for a method for removing and reusing excess electrolytes, mainly potassium, from used dialysate.

In order to remove unnecessary metabolites from the dialysis fluid, a method is known in which protonated amorphous, water-insoluble metal phosphates are used as adsorbents for Ca, Mg, and K (Patent Document 2).

Zeolite is a microporous crystalline aluminosilicate and is known to have ion exchange ability, but it is not used as a potassium adsorbent for the purpose of adjusting the amount of potassium contained in biological fluids and dialysates, etc. as mentioned above. There were no reports.

Patent No. 6884774 Special table 2019-536570 publication

When removing potassium from biological fluids, dialysates, etc. using adsorbents, there is a problem in that when conventional ion exchange materials are used, other cations such as sodium, calcium, and magnesium are also removed.

The present disclosure provides a potassium adsorbent suitable for at least one of biological fluids and dialysates, which exhibits high adsorption properties for potassium even under conditions where sodium, calcium, and magnesium are present, such as biological fluids and dialysates. The object of the present invention is to provide at least one of a manufacturing method thereof, a potassium adsorption method using the potassium adsorbent, and a potassium adsorption system using the same.

The present inventors investigated the potassium adsorption properties of compositions containing zeolite. As a result, they discovered an adsorbent in which zeolite with a specific structure exhibits high adsorption properties for potassium.

That is, the present invention is as described in the claims, and the gist of the present disclosure is as follows.
[1] Potassium adsorption for biological fluids, characterized in that the molar ratio of silica to alumina (SiO ₂ /Al ₂ O ₃ ratio) is 3 or more and 100 or less, and contains zeolite having at least an 8-membered oxygen ring. agent.
[2] The potassium for biological fluids according to [1] above, wherein the zeolite is one or more selected from the group of HEU type zeolite, FER type zeolite, YFI type zeolite, MAZ type zeolite, CHA type zeolite, and MOR type zeolite. adsorbent.
[3] The potassium adsorbent for biological fluids according to any one of [1] or [2] above, wherein the zeolite has a K ₂ O content of 3.0% by mass or less.
[4] The potassium adsorbent for biological fluids according to any one of [1] to [3] above, wherein the zeolite is a synthetic zeolite.
[5] A potassium adsorption method using the potassium adsorbent for biological fluids according to any one of [1] to [4] above.
[6] A potassium adsorption system using the potassium adsorbent for biological fluids according to any one of [1] to [4] above.
[7] Potassium adsorption for dialysate, characterized in that the molar ratio of silica to alumina (SiO ₂ /Al ₂ O ₃ ratio) is 3 or more and 100 or less, and contains zeolite having at least an 8-membered oxygen ring. agent.
[8] The potassium for dialysate according to [7] above, wherein the zeolite is one or more zeolites selected from the group of HEU type zeolite, FER type zeolite, YFI type zeolite, MAZ type zeolite, CHA type zeolite, and MOR type zeolite. adsorbent.
[9] The potassium adsorbent for dialysate according to [7] or [8], wherein the zeolite has a K ₂ O content of 3.0% by mass or less.
[10] The potassium adsorbent for dialysate according to any one of [7] to [9] above, wherein the zeolite is a synthetic zeolite.
[11] A potassium adsorption method using the potassium adsorbent for dialysate according to any one of [7] to [10] above.
[12] A potassium adsorption system using the potassium adsorbent for dialysate according to any one of [7] to [10] above.

The present disclosure provides a potassium adsorbent that exhibits high adsorption properties for potassium even under conditions where sodium, calcium, and magnesium are present, such as in biological fluids and dialysates, a method for producing the same, and a potassium adsorption method using the potassium adsorbent. Methods and/or potassium adsorption systems using the same can be provided.

Hereinafter, the zeolite according to the present disclosure will be described by showing an example of an embodiment.

The terms used in this embodiment are as follows.

"Aluminosilicate" is a composite oxide having a structure consisting of a repeating network of aluminum (Al) and silicon (Si) via oxygen (O). Among aluminosilicates, those that have a crystalline XRD peak in their powder X-ray diffraction (hereinafter also referred to as "XRD") pattern are "crystalline aluminosilicate" and those that do not have a crystalline XRD peak. This is called "amorphous aluminosilicate."

In this embodiment, the XRD pattern can be obtained by XRD measurement under the following conditions.

Accelerating current/voltage: 40mA/40kV
Radiation source: CuKα radiation (λ=1.5405Å)
Measurement mode: Step scan
Scan conditions: 40°/min
Measurement time: 3 seconds
Measurement range: 2θ=3° to 43°
Divergence vertical restriction slit: 10mm
Divergence/Incidence Slit: 1°
Light receiving slit: open
Receiving solar slit: 5°
Detector: Semiconductor detector (D/teX Ultra)
Filter: Ni filter The XRD pattern can be measured using a general powder X-ray diffraction device (eg, D8 Advance, manufactured by Bruker). In addition, a crystalline XRD peak is a peak that is detected by specifying the peak top 2θ in the analysis of an XRD pattern using general analysis software, and an XRD peak with a half-width of 2θ = 0.50° or less I can give an example.

"Zeolite" is a compound in which the skeleton atoms (hereinafter also referred to as "T atoms") have a regular structure via oxygen (O), and the T atoms are at least metal atoms and/or metalloid atoms. It is a compound consisting of Examples of the metal atoms include one or more selected from the group consisting of aluminum (Al), titanium (Ti), iron (Fe), zinc (Zn), gallium (Ga), and tin (Sn). Examples of the metalloid atoms include one or more atoms selected from the group of boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te). In this disclosure, zeolite and zeolite-like substances are different, and zeolite does not include zeolite-like substances.

A "zeolite-like substance" is a compound in which the T atoms have a regular structure via oxygen, and is a compound in which the T atoms contain at least an atom other than a metal or a metalloid. Examples of zeolite-like substances include complex phosphorus compounds containing phosphorus (P) as a T atom, such as aluminophosphate (AlPO) and silicoaluminophosphate (SAPO).

The "skeletal structure (hereinafter also referred to as "zeolite structure")" in zeolite and zeolite-like substances is the skeleton structure code (hereinafter also simply referred to as "skeleton code") defined by the Structure Commission of the International Zeolite Association. ) is the skeletal structure specified by The skeletal structure of zeolite is determined by the XRD pattern of each zeolite structure (hereinafter also referred to as "reference pattern") described in the Collection of simulated XRD powder patterns for zeolites, Fifth revised edition (2007), and the target XRD pattern of zeolite It can be identified by comparing it with Regarding the zeolite structure, skeletal structure, crystal structure or crystal phase are each used interchangeably.

A "membered ring" is a cyclic structure consisting of a T atom and an oxygen atom bonded to the T atom (hereinafter also referred to as "skeletal oxygen"). An "n-membered oxygen ring" is a membered ring, and is a cyclic structure consisting of a T atom and n skeleton oxygens (where n is an integer other than 0); for example, an "8-membered oxygen ring" is a T-atom and a cyclic structure consisting of eight skeleton oxygens. Further, the number of T atoms contained in the n-membered oxygen ring is n.

The member rings included in each zeolite structure can be confirmed from the framework of each structure code posted on the IZA homepage. For example, in the FER structure Framework, Ring sizes (#T-atoms) are 10 8 6 5. From this, it can be confirmed that the ring members included in the FER structure are a 10-membered oxygen ring, an 8-membered oxygen ring, a 6-membered oxygen ring, and a 5-membered oxygen ring.

A "biological fluid" is a liquid that flows outside the cells within an animal's body. Specific biological fluids include one or more selected from the group of blood, blood products produced from blood, plasma, lymph fluid, tissue fluid, and body cavity fluid.

"Dialysate" is a liquid used to purify biological fluids in artificial dialysis treatment.It comes into contact with biological fluids through a semipermeable membrane, etc., and removes excess water, electrolytes, and unnecessary toxins from biological fluids. It is a liquid used for

The potassium adsorbent of this embodiment has a molar ratio of silica to alumina (hereinafter also referred to as "SiO ₂ /Al ₂ O ₃ ratio") of 3 to 100, and has at least 8-membered oxygen ring pores. This is a potassium adsorbent for biological fluids and a potassium adsorbent for dialysate, which are characterized in that they contain a zeolite containing 8-membered rings (hereinafter referred to as "8-membered ring-containing zeolite").

The potassium adsorbent of this embodiment includes zeolite having a SiO ₂ /Al ₂ O ₃ molar ratio of 3 or more and 100 or less. Since the zeolite has such ^a composition, it becomes easier to adsorb potassium ions (K + ) than sodium ions (Na ⁺ ), magnesium ions (Mg ²⁺ ), and calcium ions (Ca ²⁺ ). The SiO ₂ /Al ₂ O ₃ molar ratio of the potassium adsorbent of the present embodiment is 3 or more and 100 or less, preferably 4 or more and 50 or less, and more preferably 5 or more and 40 or less. If the SiO ₂ /Al ₂ O ₃ molar ratio is not within this range, Mg ²⁺ and Ca ²⁺ will be easily adsorbed, and there is a possibility that the selective adsorption characteristics of K may deteriorate.

The zeolite contained in the potassium adsorbent of this embodiment may be zeolite produced in nature (hereinafter also referred to as "natural zeolite"), but it may be artificially produced because it has fewer impurities and tends to have higher adsorption properties. Zeolite obtained by crystallization by a hydrothermal synthesis method (hereinafter also referred to as "synthetic zeolite") is preferred.

The zeolite contained in the potassium adsorbent of this embodiment contains an 8-membered oxygen ring. As a result, the potassium adsorbent of this embodiment containing the zeolite selectively adsorbs potassium. If the zeolite does not contain an 8-membered oxygen ring, the selectivity for potassium will be low because there is no preferred membered ring that matches the size of potassium.

Zeolites containing eight-membered oxygen rings (hereinafter also referred to as "zeolites containing eight-membered rings") include, for example, ABW-type zeolites, AEI-type zeolites, AFT-type zeolites, AFV-type zeolites, AFX-type zeolites, ANA-type zeolites, BIK type zeolite, CAS type zeolite, CDO type zeolite, CHA type zeolite, DAC type zeolite, DDR type zeolite, EAB type zeolite, EEI type zeolite, ERI type zeolite, ESV type zeolite, FER type zeolite, GIS type zeolite, GME type Zeolite, HEU type zeolite, IFY type zeolite, IHW type zeolite, JBW type zeolite, KFI type zeolite, LTA type zeolite, LTF type zeolite, MAZ type zeolite, MOR type zeolite, MOZ type zeolite, MRE type zeolite, MRT type zeolite, MTF type zeolite, MWF type zeolite, OFF type zeolite, PAU type zeolite, PHI type zeolite, PWN type zeolite, RHO type zeolite, RHO type zeolite, RTE type zeolite, SAS type zeolite, SFW type zeolite, STI type zeolite, UFI type Examples include one or more selected from the group of zeolite and YFI type zeolite. The 8-membered ring-containing zeolite is preferably one or more selected from the group of HEU type zeolite, FER type zeolite, YFI type zeolite, MAZ type zeolite, CHA type zeolite and MOR type zeolite, and CHA type zeolite, FER type zeolite and More preferably, it is one or more selected from the group of HEU type zeolites.

The K ₂ O content of the potassium adsorbent of this embodiment is preferably 3.0% by mass or less, more preferably 2.5% by mass or less, and even more preferably 2.0% by mass. The K ₂ O content is calculated as K 2 O based on the total mass of zeolite silicon (Si) converted into SiO ₂ , aluminum (Al) converted into Al ₂ O ₃ , and potassium (K) converted into _{K 2 O.} It is the mass proportion [mass %] of potassium (K).

The zeolite contained in the potassium adsorbent of this embodiment may contain T atoms other than Si and Al. Examples of T atoms constituting the zeolite include one or more selected from the group of boron (B), gallium (Ga), germanium (Ge), iron (Fe), titanium (Ti), and tin (Sn). etc. can be mentioned.

As the ions (M) contained in the zeolite contained in the potassium adsorbent of this embodiment, one or more ions selected from the group of hydrogen ions (H ⁺ ), Na ⁺ , Ca ²⁺ and Mg ²⁺ can be exemplified. Ions in the zeolite can be replaced by other ions by ion exchange.

The zeolite contained in the potassium adsorbent of this embodiment has a molar ratio of cation (M) calculated as an oxide to alumina ( _hereinafter also referred to as "M2 _/n O/ _Al2O3 ratio". However, n is M ) exceeds 0.1, it is assumed that the cation type is the ion (M) type. Further, when the zeolite contains multiple types of cations, the zeolite may be considered to be a cation type (for example, a sodium/hydrogen ion type) consisting of multiple cations.

The cation type of the zeolite contained in the potassium adsorbent of this embodiment includes one or more selected from the group of H ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ , and Mg ²⁺ , and preferably H ⁺ type and Na ⁺ At least one of the types, more preferably the Na ⁺ type.

Although the potassium adsorbent of the present embodiment may contain an organic structure directing agent (hereinafter also referred to as "SDA"), it is preferable that it does not contain SDA in order to easily improve the potassium adsorption performance. preferable. An example of a realistic SDA content of a potassium adsorbent is an SDA/SiO ₂ ratio of more than 0 and less than 0.005. Specific SDA includes amines or quaternary ammonium cations. As the amine or quaternary ammonium cation, for example, one or more selected from the group of tetraalkylammonium cation, N,N,N-trialkyladamantane ammonium cation, N,N,N-trialkylcyclohexylammonium cation, pyridine, and piperidine. can be mentioned.

The K capture rate of the potassium adsorbent of this embodiment is preferably 20% or more and 100% or less, more preferably 30% or more and 99% or less, and even more preferably 40% or more and 98% or less.

The Na capture rate of the potassium adsorbent of this embodiment is preferably -10% or more and 20% or less, more preferably -6% or more and 10% or less, and preferably -4% or more and 5% or less. More preferred.

The Mg capture rate of the potassium adsorbent of this embodiment is preferably -5% or more and 15% or less, more preferably -2% or more and 10% or less, and even more preferably 0% or more and 6% or less. preferable.

The Ca capture rate of the potassium adsorbent of this embodiment is preferably -5% or more and 50% or less, more preferably -2% or more and 40% or less, and even more preferably 0% or more and 30% or less. preferable.

The K separation coefficient for Na of the potassium adsorbent of the present embodiment is preferably 3 or more and 10,000 or less, more preferably 5 or more and 1,000 or less, and even more preferably 10 or more and 500 or less.

The K separation coefficient for Mg of the potassium adsorbent of the present embodiment is preferably 5 or more and 100,000 or less, more preferably 10 or more and 10,000 or less, and even more preferably 15 or more and 2,000 or less.

The K separation coefficient for Ca of the potassium adsorbent of the present embodiment is preferably 1 or more and 10,000 or less, more preferably 1.5 or more and 3,000 or less, and even more preferably 2 or more and 1,000 or less.

The potassium adsorbent of this embodiment can be used in any shape depending on the purpose, and is not particularly limited, but can be used, for example, in the form of a powder, a molded body, or an adsorption member. Specific examples of the shape of the molded body include one or more selected from the group consisting of spherical, substantially spherical, elliptical, disk-like, cylindrical, polyhedral, irregularly shaped, and petal-like.

When used as a molded article, the potassium adsorbent of this embodiment may contain a binder. As the binder, any known binder for zeolite may be used, such as one or more selected from the group of silica, alumina, kaolin, attapulgite, montmorillonite, bentonite, allophane, and sepiolite. .

The potassium adsorbent of this embodiment can be used in a method for adsorbing potassium ions. The potassium ion adsorption method using the potassium adsorbent of this embodiment is arbitrary, but for example, a potassium ion adsorption method having a batch process of dispersing the potassium ion adsorption agent of this embodiment in a potassium ion-containing fluid; Alternatively, there may be mentioned a method for adsorbing potassium ions, which includes a step of flowing a potassium ion-containing fluid through the potassium adsorbent of this embodiment.

The potassium adsorbent used in the step of bringing the potassium ion-containing fluid into contact with the potassium adsorbent of this embodiment (hereinafter also referred to as "potassium adsorption step") may contain the potassium adsorbent of this embodiment, It may be two or more potassium adsorbents containing zeolites different in at least any of the compositions and zeolite structures, and furthermore, the potassium adsorbent of this embodiment and the potassium adsorbent containing zeolites other than the 8-membered ring-containing zeolite. It may contain an agent.

The potassium content of the potassium ion-containing fluid to be subjected to the potassium adsorption step is arbitrary, and may be, for example, 1 mmol/L or more and 1000 mmol/L, or 3 mmol/L or more and 100 mmol/L or less.

It is preferable that the potassium ion-containing fluid contains one or more selected from the group of sodium ions, magnesium ions, and calcium ions from the viewpoint of expressing potassium selectivity.

The potassium ion-containing fluid may contain one or more substances selected from the group of proteins, amino acids, vitamins, and other biomolecules in addition to inorganic ions.

When the potassium adsorbent of this embodiment is a potassium adsorbent for biological fluids, the potassium ion-containing fluid to be subjected to the potassium adsorption step may be a biological fluid. Specific biological fluids include one or more selected from the group of blood, blood products produced from blood, plasma, lymph fluid, interstitial fluid, and body cavity fluid. Preferred biological fluids include one or more selected from the group of blood, blood products produced from blood, and plasma.

When the potassium adsorbent of this embodiment is a potassium adsorbent for dialysate, the potassium ion-containing fluid to be subjected to the potassium adsorption step may be a dialysate.

The potassium adsorbent of this embodiment can be used as a potassium adsorption system including the same. The potassium adsorption system may include the potassium adsorbent of this embodiment, and at least one of an activated carbon adsorbent and a hollow fiber membrane.

Next, a method for manufacturing the potassium adsorbent of this embodiment will be explained.

The potassium adsorbent of this embodiment can be produced using any method as long as it can be obtained as long as it satisfies the above configuration.

As a method for producing the 8-membered ring-containing zeolite contained in the potassium adsorbent of the present embodiment, a step (hereinafter referred to as " ), a process of washing the 8-membered ring-containing zeolite (hereinafter also referred to as the ``washing process''), a process of drying the 8-membered ring-containing zeolite (hereinafter also referred to as the ``drying process''). and a process of heat-treating an 8-membered ring-containing zeolite (hereinafter also referred to as "activation process").

When an 8-membered ring-containing zeolite is obtained by a crystallization step, a composition containing at least a silica source, an alumina source, an alkali source, and water (hereinafter also referred to as "raw material composition") may be crystallized. Any commercially available zeolite may be used as the 8-membered ring-containing zeolite as long as it satisfies the above configuration.

The silica source is at least one of a silicon-containing compound and silicon (Si), such as silica sol, fumed silica, colloidal silica, precipitated silica, sodium silicate, potassium silicate, amorphous silicic acid, and amorphous silica. Examples include one or more selected from the group of silica, crystalline aluminosilicate, and amorphous aluminosilicate.

The alumina source is at least one of an aluminum-containing compound and aluminum (Al), such as aluminum hydroxide, aluminum hydroxide oxide, aluminum oxide, aluminum sulfate, aluminum nitrate, sodium aluminate, potassium aluminate, aluminum chloride, Examples include one or more selected from the group of crystalline aluminosilicate and amorphous aluminosilicate.

The alkali source is at least one of a compound containing an alkali metal element and an alkali metal, and is selected from the group of hydroxides, carbonates, sulfates, chlorides, bromides, silicates, and iodides of alkali metals. It is preferably one or more selected from the group of hydroxides, chlorides, bromides and iodides, and more preferably hydroxides.

Examples of the alkali metal element include one or more selected from the group of sodium, potassium, rubidium, and cesium, with at least one of sodium and potassium being preferred.

Water may be distilled water, deionized water, or pure water. Furthermore, water derived from other starting materials contained in the raw material composition, such as solvents and hydrous compounds, can also be considered as water in the raw material composition.

The raw material composition may contain an organic structure directing agent (hereinafter also referred to as "SDA") in order to increase the directivity toward zeolite having a specific skeleton structure. Examples of the SDA directed toward zeolite include one or more selected from the group of tetraalkylammonium cations, N,N,N-trialkyladamantane ammonium cations, N,N,N-trialkylcyclohexylammonium cations, pyridine, and piperidine. Can be mentioned.

The raw material composition may include a sufficiently small amount of seed crystals relative to the silica and alumina sources, as this tends to reduce the processing time required for crystallization. The seed crystal may be zeolite. The seed crystals mixed into the raw material composition are the amount of aluminum and silicon in the seed crystals relative to the total mass of aluminum and silicon in the raw material composition (not including seed crystals) in terms of Al ₂ O ₃ and SiO _{2 ,} respectively. The ratio of the total mass calculated as Al ₂ O ₃ and SiO ₂ (hereinafter also referred to as "seed crystal content") is 0 mass % or more and 20 mass % or less or 10 mass % or less, respectively. One thing can be mentioned.

As a preferable composition of the raw material composition, the molar composition may be adjusted so that it becomes an 8-membered ring-containing zeolite. For example, when the 8-membered ring-containing zeolite is a CHA type, the raw material composition may have the following molar composition.

SiO ₂ /Al ₂ O ₃ ratio = 3 to 200, 4 to 100, or 5 to 60 K/SiO ₂ ratio = 0.00 to 1.50, 0.00 to 0.90, or 0.00 0.70 or more Na/SiO ₂ ratio = 0.00 or more and 1.50 or less, 0.00 or more and 0.90 or 0.00 or more and 0.70 or less OH/SiO ₂ ratio = 0.10 or more and 3.00 Below, 0.15 to 2.00 or 0.20 to 1.50 SDA/ _SiO2 ratio = 0.00 to 1.00, 0.00 to 0.70, or 0.00 to 0.40 The following _H2O / _SiO2 ratio = 2 or more and 1000 or less, 6 or more and 500 or less, or 10 and 100 or less When the potassium content of the 8-membered ring-containing zeolite exceeds 3.0% by mass, the zeolite is subjected to a potassium removal step. It is preferable.

In the potassium removal step, an arbitrary cation type can be obtained by removing alkali metals such as potassium contained in the ion exchange sites and pores of the 8-membered ring-containing zeolite. Examples of methods for removing alkali metal include one or more selected from the group of liquid phase treatment using an electrolyte solution and exchange treatment using a resin.

When replacing with hydrogen ions, at least one of a method of treating an 8-membered ring-containing zeolite with an acid, and a method of performing a liquid phase treatment of an 8-membered ring-containing zeolite with an ammonium (NH ₄ ⁺ )-containing compound and then heat-treating the zeolite can be mentioned. .

When replacing with Na ⁺ , any method is sufficient as long as the 8-membered ring-containing zeolite and the sodium source are brought into sufficient contact with each other, and examples include at least one of wet mixing and dry mixing. This results in a zeolite with increased sodium content. Preferred mixing methods include one or more methods selected from the group of flowing an aqueous solution containing a sodium source through an 8-membered ring-containing zeolite, ion exchange, liquid phase treatment with an electrolyte solution containing a sodium source, impregnating and supporting, and evaporation to dryness. Preferably, at least one of liquid phase treatment and ion exchange using an electrolyte solution containing a sodium source can be exemplified.

The sodium source may be at least one of a compound and a complex containing sodium, and is preferably a water-soluble sodium compound. Specific sodium sources include sodium fluoride, sodium chloride, sodium bromide, sodium nitrate, sodium carbonate, sodium hydrogen carbonate, sodium sulfate, sodium hydrogen sulfate, sodium phosphate, sodium monohydrogen phosphate, and sodium dihydrogen phosphate. , one or more selected from the group of sodium acetate, sodium citrate and sodium oxalate, preferably one or more selected from the group of sodium chloride, sodium bromide, sodium nitrate, sodium hydrogen carbonate, sodium sulfate and sodium hydrogen sulfate. Preferably, one or more selected from the group of sodium chloride, sodium bromide, and sodium nitrate, and more preferably at least one of sodium chloride and sodium nitrate.

An example of the mixing may be bringing the raw material zeolite and the aqueous solution containing the water-soluble sodium source into contact at a temperature of 10° C. or more and 100° C. or less for 10 seconds or more and 10 hours or less.

Note that for 8-membered ring-containing zeolites that are of the desired cation type in advance or 8-membered ring-containing zeolites that have a sufficiently small potassium content, the 8-membered ring-containing zeolites may be directly contained in the adsorbent without being subjected to the potassium removal step. By doing so, it may be used as the potassium adsorbent of this embodiment.

The 8-membered ring-containing zeolite is preferably one or more selected from the group of CHA type zeolite, FER type zeolite, GME type zeolite, HEU type zeolite, MAZ type zeolite, MER type zeolite, MOR type zeolite, and YFI type zeolite, and CHA type zeolite , FER type zeolite, and HEU type zeolite. As the 8-membered ring-containing zeolite, it is preferable to select a zeolite suitable for the potassium ion-containing fluid to be brought into contact with the potassium adsorbent of this embodiment. From the viewpoint of obtaining a potassium adsorbent with a higher K separation coefficient for Na ⁺ , the 8-membered ring-containing zeolite is more preferably a HEU type zeolite. On the other hand, from the viewpoint of obtaining a potassium adsorbent with a higher K separation coefficient for Ca ²⁺ , it is more preferable that the 8-membered ring-containing zeolite is a FER type zeolite.

The SiO ₂ /Al ₂ O ₃ ratio of the 8-membered ring-containing zeolite may be the same as that of the zeolite contained in the potassium adsorbent of this embodiment, preferably 3 or more and 100 or less, more preferably 4 or more and 50 or less, and 5 It is more preferably 40 or less.

The method for producing a potassium adsorbent of the present embodiment may include one or more steps selected from the group of a washing step, a drying step, and an activation step, as necessary.

In order to remove impurities contained in the 8-membered ring-containing zeolite, it may be subjected to a washing step. The washing step may be performed using any washing method as long as impurities and the like can be removed from the 8-membered ring-containing zeolite. An example of the cleaning method is to flow a sufficient amount of pure water through the 8-membered ring pore-containing zeolite.

In order to remove residual moisture from the surface, pores, etc. of the 8-membered ring-containing zeolite, it may be subjected to a drying process. The drying step may be performed using any drying method as long as it can remove moisture remaining on the surface, pores, etc. of the 8-membered ring-containing zeolite. An example of the drying method is treatment in the air at a temperature of 80° C. or higher and 200° C. or lower, preferably 100° C. or higher and 190° C. or lower.

In order to remove impurities such as organic substances from the 8-membered ring-containing zeolite, it may be subjected to an activation step. The activation step may be any heat treatment as long as organic matter can be removed from the 8-membered ring-containing zeolite. In the atmosphere as a heat treatment method. Examples include processing at 400°C or higher and 700°C or lower, and further, processing at 500°C or higher and 600°C or lower in the atmosphere.

When applying the potassium adsorbent of this embodiment to a base material, the method for producing the potassium adsorbent of this embodiment includes a step of mixing an 8-membered ring-containing zeolite and a solvent (hereinafter referred to as "slurrying step"). It is preferable.

The slurrying step yields a sodium-containing zeolite slurry. Any method for mixing the 8-membered ring-containing zeolite and the solvent can be used as long as a zeolite slurry suitable for coating the desired substrate can be obtained. As a mixing method in the slurry forming step, the 8-membered ring-containing zeolite may be added to and mixed with at least one of water and alcohol, preferably water.

The 8-membered ring-containing zeolite obtained by the above process can be used as it is as the potassium adsorbent of this embodiment.

When the potassium adsorbent of this embodiment is made into a molded article, it is preferable to include a step of molding an 8-membered ring-containing zeolite (hereinafter also referred to as a "molding step").

In the shaping step, the 8-membered ring-containing zeolite is shaped into a desired shape. The molding method in the molding step may be any method as long as it can obtain a molded product of the desired shape, and is selected from the group of, for example, rolling granulation molding, press molding, extrusion molding, injection molding, cast molding, and sheet molding. 1 or more.

In the molding process, a composition mixed with a binder in addition to the 8-membered ring-containing zeolite may be molded. The binder may be a known binder for zeolite, such as one or more selected from the group of silica, alumina, kaolin, attapulgite, montmorillonite, bentonite, allophane, and sepiolite.

(Identification of crystal structure)
The sample was subjected to XRD measurement using an X-ray diffraction device (device name: Ultima IV Protectus, manufactured by Rigaku Corporation). The measurement conditions are as follows.

Accelerating current/voltage: 40mA/40kV
Radiation source: CuKα radiation (λ=1.5405Å)
Measurement mode: continuous scan
Scan conditions: 40°/min
Measurement range: 2θ=3° to 43°
Divergence vertical restriction slit: 10mm
Divergence/Incidence Slit: 1°
Light receiving slit: open
Receiving solar slit: 5°
Detector: Semiconductor detector (D/teX Ultra)
Filter: Ni filter The zeolite structure was identified by comparing the obtained XRD pattern with a reference pattern.

(composition analysis)
A sample solution was prepared by dissolving the sample in a mixed aqueous solution of hydrofluoric acid and nitric acid. The sample solution was measured by inductively coupled plasma emission spectroscopy (ICP-AES) using a general ICP device (device name: OPTIMA5300DV, manufactured by PerkinElmer). From the obtained measured values of Si and Al, the SiO ₂ /Al ₂ O ₃ molar ratio of the sample and the contained aluminum mass were determined.

"M capture rate" and "K separation coefficient for M" are values measured by the following method.

(Adsorption characteristics evaluation)
<Measurement sample>
Shape: Powdered adsorbent <Potassium-containing electrolyte aqueous solution>
Powder for preparing artificial seawater (product name: Marine Art SF-1, manufactured by Tomita Pharmaceutical Co., Ltd.) is dissolved in pure water to prepare.

Na concentration: 435 mmol/L
K concentration: 9.0 mmol/L
Mg concentration: 48.7 mmol/L
Ca concentration: 10.2 mmol/L
<Potassium adsorption conditions>
A slurry was prepared by dispersing 2 g of the sample to be measured in 100 mL of the above aqueous solution, and the slurry was stirred at room temperature for 20 hours. The sample was collected by filtration and dried at 110°C for 20 hours.

The compositions of the solid phase samples before and after the evaluation were each analyzed by ICP. Further, the water content of the sample was analyzed by the ignition loss method at 600° C., and the dry weight was determined. The composition of the liquid phase after evaluation was calculated from the composition of the solid phase sample by mass balance.

<M capture rate>
The capture rate of ions M (M = Na ⁺ , K ⁺ , Mg ²⁺ or Ca ²⁺ ) (hereinafter also referred to as "M capture rate") is the proportion of M trapped in the measurement sample out of the M present in the system. It is a ratio and was calculated using the following formula.

M capture rate [%] = (Number of moles of M captured in the measurement sample by evaluation) / (Number of moles of M contained in the liquid phase before evaluation) x 100
In addition, when the calculated value of the capture rate was negative, it was assumed that M contained in the sample was eluted into the liquid phase at the time before evaluation.

<K separation factor for M>
The separation coefficient of K with respect to ion M (M = Na ⁺ , Mg ²⁺ or Ca ²⁺ ) (hereinafter also referred to as "K separation coefficient with respect to M") is an index of the adsorption selectivity of K with respect to M of the measurement sample, Calculated using the formula below.

K separation coefficient for M = (K adsorption rate/(100-K adsorption rate))/(M adsorption rate/(100-M adsorption rate))
M adsorption rate [%] = (Number of moles of M contained in the sample after evaluation) / (Total number of moles of M contained in the evaluation liquid and sample) x 100
Example 1
FER type zeolite whose cation type is K ⁺ type (product name: HSZ (registered trademark)-720KOA, manufactured by Tosoh Corporation; SiO ₂ /Al ₂ O ₃ = 17.5, Na ₂ O: 1.7% by mass, K ₂ O: 5.0% by mass) was mixed with 10 times the mass of water, and a cake was created by suction filtration. An aqueous sodium chloride solution (10% by mass) of 11 times the mass of the zeolite was passed through the cake, and then hot water of 10 times the mass of the zeolite was passed through the cake. The flow of the sodium chloride aqueous solution and hot water was repeated two more times. Next, the obtained cake was dried at 110° C. in the air for 20 hours to produce FER type zeolite with reduced potassium content (SiO ₂ /Al ₂ O ₃ = 18, Na ₂ O: 4.2% by mass, K ₂ O: 0.89% by mass) was obtained, which was used as a potassium adsorbent for biological fluids and a potassium adsorbent for dialysate of this example.

Example 2
Pure water, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, and an amorphous aluminosilicate were mixed to have the following molar composition to obtain a raw material composition.

SiO ₂ /Al ₂ O ₃ = 11.7
Na/ _SiO2 = 0.10
K/ _SiO2 = 0.24
_H2O / _SiO2 = 15
OH/ _SiO2 =0.34
To the obtained raw material composition, 2% by mass of natural clinoptilolite (product name: Iwamilite, manufactured by Mitsui Kinzoku Exploration Co., Ltd.) was added as a seed crystal based on the mass of the raw material composition, and the mixture was filled into an 80 mL autoclave and stirred. While heating at 150° C. for 72 hours, the mixture was crystallized. After crystallization, it is cooled, filtered, washed, and dried at 110° C. in the air for 20 hours to obtain a HEU type zeolite crystallized product (SiO ₂ /Al ₂ O ₃ = 9.6, Na ₂ O: 0.80% by mass). , K ₂ O: 10.9% by mass) was obtained.

Next, the zeolite was mixed with 10 times the mass of water, and a cake was created by suction filtration. An aqueous sodium chloride solution (18% by mass) of 24 times the mass of the zeolite was passed through the cake, and then hot water of 20 times the mass of the zeolite was passed through the cake. The flow of the sodium chloride aqueous solution and hot water was repeated once more. Next, the obtained cake was dried at 110° C. in the air for 20 hours to obtain HEU type zeolite with reduced potassium content (SiO ₂ /Al ₂ O ₃ = 18, Na ₂ O: 4.2% by mass, K ₂ O: 0.89% by mass) was obtained, which was used as a potassium adsorbent for biological fluids and a potassium adsorbent for dialysate of this example.

Example 3
A HEU type zeolite crystallized product was obtained in the same manner as in Example 2. Next, the same method as in Example 1 was carried out except that the zeolite was used, and HEU type zeolite with a reduced amount of potassium (SiO ₂ /Al ₂ O ₃ = 9.6, Na ₂ O: 7.3 % by mass, K ₂ O: 1.1% by mass), which was used as the potassium adsorbent for biological fluids and the potassium adsorbent for dialysate of this example.

Example 4
A raw material having the following molar composition is obtained by mixing FAU type zeolite (product name: HSZ (registered trademark)-331HSA, manufactured by Tosoh Corporation; SiO ₂ /Al ₂ O ₃ = 6.3), potassium hydroxide aqueous solution, and water. A composition was obtained.

SiO ₂ /Al ₂ O ₃ = 6.3
K/ _SiO2 = 0.77
_H2O / _SiO2 = 40
OH/ _SiO2 =0.77
The obtained raw material composition was filled into a 500 mL polypropylene bottle, and crystallized by standing at 95° C. for 96 hours. After crystallization, it is cooled, filtered, washed, and dried at 110° C. in the air for 20 hours to obtain a CHA type zeolite crystallized product (SiO ₂ /Al ₂ O ₃ = 5.4, K ₂ O: 18.1% by mass). ) was obtained.

Next, the same method as in Example 1 was carried out except that the zeolite was used, and a CHA type zeolite with a reduced amount of potassium (SiO ₂ /Al ₂ O ₃ = 5.4, Na ₂ O: 13.2 mass %, K ₂ O: 0.02% by mass), which was used as the potassium adsorbent for biological fluids and the potassium adsorbent for dialysate of this example.

Example 5
Dimethylethylcyclohexylammonium (hereinafter also referred to as "DMECH") hydroxide aqueous solution, sodium hydroxide aqueous solution, water, and amorphous aluminosilicate (SiO ₂ /Al ₂ O ₃ = 10.6) are mixed to form the following. A raw material composition having a molar composition of was obtained.

SiO ₂ /Al ₂ O ₃ = 10.6
DMECH/ _SiO2 = 0.08
Na/ _SiO2 = 0.29
_H2O / _SiO2 = 18
OH/ _SiO2 = 0.37
After adding and mixing CHA type zeolite as a seed crystal to the obtained raw material composition so as to have a concentration of 2.0% by mass, this was filled into an 80 mL autoclave and hydrothermally treated at 160°C for 48 hours to obtain CHA type zeolite. A crystallized product consisting of a single phase of zeolite was obtained. The obtained crystallized product was recovered by solid-liquid separation, washed with a sufficient amount of pure water, dried in the air, and then calcined at 600°C. The obtained CHA type zeolite (SiO ₂ /Al ₂ O ₃ = 9.6, Na ₂ O: 6.7 mass %, K ₂ O: less than 0.1 mass % (detection limit)) was It was used as a potassium adsorbent for body fluids and a potassium adsorbent for dialysate.

Example 6
Sodium hydroxide, sodium aluminate aqueous solution (Na ₂ O: 19.4% by mass, Al ₂ O ₃ : 20.1% by mass), and amorphous silica (product name: Nipsil, manufactured by Tosoh Silica Co., Ltd.) A raw material composition having the following molar composition was obtained by mixing.

SiO ₂ /Al ₂ O ₃ = 20.0
Na/ _SiO2 = 0.21
_H2O / _SiO2 = 20
OH/ _SiO2 = 0.21
The obtained raw material composition was filled into an autoclave and hydrothermally treated at 160°C for 48 hours under stirring conditions to obtain a crystallized product. The obtained crystallized product was collected by solid-liquid separation, washed with a sufficient amount of pure water, and dried at 110° C. in the atmosphere. The obtained MOR type zeolite (SiO ₂ /Al ₂ O ₃ = 18.7, Na ₂ O: 5.0 mass %, K ₂ O: less than 0.1 mass % (detection limit)) was It was used as a potassium adsorbent for body fluids and a potassium adsorbent for dialysate.

Example 7
Colloidal silica (product name: AS-40, manufactured by GRACE), dimethyldipropylammonium (hereinafter also referred to as "DMDPA") hydroxide aqueous solution, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and water were mixed. The obtained liquid mixture was filled into an 80 mL autoclave and stirred at about 60° C. for about 3 hours under rotation conditions of 20 rpm, and then the container was cooled to room temperature. Next, Y-type zeolite (product name: HSZ-350HUA, manufactured by Tosoh Corporation) was added to obtain a raw material composition having the following molar composition.

SiO ₂ /Al ₂ O ₃ = 40
DMDPA/ _SiO2 = 0.17
Na/ _SiO2 = 0.15
K/ _SiO2 = 0.17
_H2O / _SiO2 = 7.0
OH/ _SiO2 = 0.49
The obtained raw material composition was crystallized at 160° C. for 6 days using an 80 mL autoclave. After crystallization, the YFI type zeolite (SiO ₂ /Al ₂ O ₃ = 18, Na ₂ O: 0.03 mass %, K ₂ O: 4.1 mass %) was calcined in the air at 550° C. for 2 hours. Obtained.

Next, the same method as in Example 1 was carried out except that the zeolite was used, and a YFI type zeolite with a reduced amount of potassium (SiO ₂ /Al ₂ O ₃ = 18, Na ₂ O: 13.2% by mass) was prepared. , K ₂ O: 0.02% by mass) and used as a potassium adsorbent for biological fluids and a potassium adsorbent for dialysate of this example.

Example 8
Colloidal silica (product name: AS-40, manufactured by GRACE), Y-type zeolite (product name: HSZ (registered trademark)-320NAA, manufactured by Tosoh Corporation), tetramethylammonium (hereinafter also referred to as "TMA") hydroxide An aqueous sodium hydroxide solution, an aqueous sodium hydroxide solution, and water were mixed to obtain a raw material composition having the following molar composition.

SiO ₂ /Al ₂ O ₃ = 15
TMA/ _SiO2 = 0.04
Na/ _SiO2 = 0.56
_H2O / _SiO2 = 15.0
OH/ _SiO2 = 0.60
The obtained raw material composition was crystallized using an 80 mL autoclave at 140° C. for 48 hours under stirring conditions. The obtained crystallized product was recovered by solid-liquid separation, washed with a sufficient amount of pure water, dried in the air, and then calcined at 600°C. The obtained MAZ type zeolite (SiO ₂ /Al ₂ O ₃ = 8.4, Na ₂ O: 6.9 mass %, K ₂ O: less than 0.1 mass % (detection limit)) was It was used as a potassium adsorbent for body fluids and a potassium adsorbent for dialysate.

Comparative example 1
LTA type zeolite (product name: A-4, manufactured by Tosoh Zeorum Co., Ltd.; SiO ₂ /Al ₂ O ₃ = 2.2, Na ₂ O: 20.9 mass %, K ₂ O: less than 0.1 mass % ( The detection limit)) was used as the adsorbent in this comparative example.

Comparative example 2
FAU type zeolite (product name: F-9, manufactured by Tosoh Zeorum Co., Ltd.; SiO ₂ /Al ₂ O ₃ = 2.7, Na ₂ O: 19.1% by mass, K ₂ O: less than 0.1% by mass ( The detection limit)) was used as the adsorbent in this comparative example.

Comparative example 3
FAU type zeolite (product name: HSZ (registered trademark)-320NAA, manufactured by Tosoh Corporation; SiO ₂ /Al ₂ O ₃ = 5.7, Na ₂ O: 12.2 mass %, K ₂ O: 0.1 mass % (detection limit)) was used as the adsorbent for this comparative example.

Comparative example 4
^* BEA type zeolite (product name: HSZ (registered trademark)-920NHA, manufactured by Tosoh Corporation; SiO ₂ /Al ₂ O ₃ = 17.5, K ₂ O: less than 0.1% by mass (detection limit)) at 600°C. After baking for 2 hours to remove ammonium, it was used as an adsorbent for this comparative example.

Comparative example 5
FER type zeolite (product name: HSZ (registered trademark)-720KOA, manufactured by Tosoh Corporation; SiO ₂ /Al ₂ O ₃ = 17.5, Na ₂ O: 1.7 mass %, K ₂ O: 5.0 mass % ) was used as the adsorbent for this comparative example.

Adsorption characteristics were evaluated for the potassium adsorbents obtained in Examples and Comparative Examples.

The evaluation results are shown in Table 1.

From Table 1, the K separation coefficient for Na and the K separation coefficient for Mg in Examples 1 to 7 are all 10 or more. On the other hand, the K separation coefficient for Na and the K separation coefficient for Mg of samples with a SiO ₂ /Al ₂ O ₃ molar ratio of 3 or less (Comparative Examples 1 and 2) or without 8-membered ring pores (Comparative Examples 2 to 4) are all 10 or less.

In addition, in samples where the SiO ₂ /Al ₂ O ₃ molar ratio is 3 or less (Comparative Examples 1 and 2), the separation coefficient of K with respect to Ca is 1 or less, and the capture rate of Ca is 50% or more. On the other hand, for all samples with a SiO ₂ /Al ₂ O ₃ molar ratio of 5 or more, the separation coefficient of K with respect to Ca is 2 or more and the capture rate of Ca is 30% or less.

Furthermore, in the sample with a K ₂ O content exceeding 3.0% by mass (Comparative Example 5), the K capture rate was a negative value, indicating that K was released without being adsorbed.

Claims (14)

A potassium adsorbent for biological fluids, characterized in that the molar ratio of silica to alumina (SiO ₂ /Al ₂ O ₃ ratio) is 3 or more and 100 or less, and further contains zeolite having at least an 8-membered oxygen ring. The potassium adsorbent for biological fluids according to claim 1, wherein the zeolite is one or more selected from the group of HEU type zeolite, FER type zeolite, YFI type zeolite, MAZ type zeolite, CHA type zeolite, and MOR type zeolite. The potassium adsorbent for biological fluids according to claim 1 or 2, wherein the zeolite has a K ₂ O content of 3.0% by mass or less. The potassium adsorbent for biological fluids according to any one of claims 1 to 3, wherein the zeolite is a synthetic zeolite. A method for producing a potassium adsorbent for biological fluids according to any one of claims 1 to 4. A method for adsorbing potassium using the potassium adsorbent for biological fluids according to any one of claims 1 to 5. A potassium adsorption system using the potassium adsorbent for biological fluids according to any one of claims 1 to 5. A potassium adsorbent for dialysate, characterized in that the molar ratio of silica to alumina (SiO ₂ /Al ₂ O ₃ ratio) is 3 or more and 100 or less, and further contains zeolite having at least an 8-membered oxygen ring. The potassium adsorbent for dialysate according to claim 8, wherein the zeolite is one or more zeolites selected from the group of HEU type zeolite, FER type zeolite, YFI type zeolite, MAZ type zeolite, CHA type zeolite, and MOR type zeolite. The potassium adsorbent for dialysate according to claim 8 or 9, wherein the zeolite has a K ₂ O content of 3.0% by mass or less. The potassium adsorbent for dialysate according to any one of claims 8 to 10, wherein the zeolite is a synthetic zeolite. A method for producing a potassium adsorbent for dialysate according to any one of claims 8 to 11. A method for adsorbing potassium using the potassium adsorbent for dialysate according to any one of claims 8 to 11. A potassium adsorption system using the potassium adsorbent for dialysate according to any one of claims 8 to 11.