JP4189492B2 - Layered double hydroxide / zeolite composite - Google Patents

Description

The present invention has a coating structure of a core made of zeolite and a shell made of layered double hydroxide, has a complex adsorption function such as simultaneous removal of NH ₄ ⁺ and PO ₄ ³⁻ , and is generally used. The present invention relates to a layered double hydroxide / zeolite composite excellent in impurity removal efficiency at a liquid flow rate and a method for producing the same.

As an important use of the porous material, an adsorbent can be mentioned. There are various driving forces for this porous body to adsorb ions, gases, fine particles, etc., one of which is a chemical action. From this point of view, the adsorbent can be roughly divided into two. For example, alumina-silica gel, zeolite, etc. have solid acidity and strongly adsorb basic substances such as ammonia. On the other hand, MgO, CaO 2 and the like have solid basicity and can strongly adsorb acidic substances such as hydrogen sulfide. Thus, many adsorbents can adsorb only acidic or basic substances.

The adsorbents having or adhering to the composite adsorption function have not been studied so much so far, and the fly-pontite ([Zn _{6 -X} Al _X ] [Si _4-X Al _X ] O ₁₀ [OH] ₈ )
A composite of silica gel and a composite of zeolite and sepiolite are known.
In the former case, amphoteric adsorption ability has been reported for fly-pontite, but it does not have such a high double adsorption ability due to its low specific surface area and poor crystallinity. In the latter, only lower adsorption capacity is obtained. Further, a layered double hydroxide is known as an anion adsorbent, but a layered double hydroxide-alumina silica gel composite (Patent Document 1) has been reported as a composite using such a substance. There is only.
JP 2002-159849 A

Ceramic porous bodies are generally excellent in heat resistance, chemical resistance, and weather resistance, and many materials are environmentally friendly. From such a viewpoint, it is suitable as a material for the maintenance and purification of air and water environment. Considering such applications, for example, it is necessary to remove both ammonia and phosphate ions at the same time for water quality conservation in lakes and rivers, and the development of adsorbents having such amphoteric adsorption ability is required. ing.

That is, in recent years, acidic gases such as H ₂ S, CO ₂ and mercaptans, basic gases such as NH ₃ and amines, and NH ₄ ⁺ and PO ₄ ³⁻ for water purification are simultaneously removed for the purpose of environmental purification and deodorization. Development of adsorbents with multiple adsorption functions is required.

The present invention has been made in view of such problems, and provides a layered double hydroxide / zeolite composite having a high adsorbability for both acidic and basic substances and a method for producing the same. Another object is to provide an adsorbent containing the layered double hydroxide / zeolite composite.

As a result of intensive studies to improve the above-mentioned problems, the present inventors have synthesized a complex composed of zeolite that adsorbs a large amount of a basic substance and a layered double hydroxide that strongly adsorbs an acidic substance. The present inventors have found that the problems can be solved and have completed the present invention.

That is, this invention was solved by taking the structure shown by the following [1]-[ 7 ].
[1] An adsorbent that adsorbs a harmful substance comprising a ceramic porous body, wherein the ceramic porous body is a non-stoichiometric compound represented by the following general formula (a) or (b): It is characterized by comprising a layered double hydroxide / zeolite composite containing A) and zeolite (B).

[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} [A ^n- _{x / n} · mH ₂ O] ^x- (a)
[Al ₂ Li (OH) ₆ ] ^{x +} [A ⁿ⁻ _{x / n} · mH ₂ O] ^x− (b)
(Where 0.1 ≦ x ≦ 0.4, 0 <m, n is a natural number from 1 to 4, M ²⁺ is represented by Mg, Ca, Mn, Fe, Co, Ni, Cu, Zn, etc. At least one divalent metal, M ³⁺ is at least one trivalent metal represented by Al, Fe, Cr, Co, Ga, In, etc., An ⁻ is OH ⁻ , Cl ⁻ , Br ⁻ , CO ₃ ²⁻ , NO ₃ ²⁻ , SO ₄ ²⁻ , Fe (CN) ₆ ⁴⁻ , at least one of n-valent ion-exchangeable anions represented by tartrate ions.
[2] The ion exchange capacity of the zeolite (B) is characterized in that at 1.0Mmolg- ¹ or more [1] adsorbents according.
[3] The zeolite (B) is characterized in that it is a type A zeolite [1] or [2] adsorbents according to any one.
[4] to the zeolite (B) is [1], characterized in that an X-type zeolite, adsorbents according to any one of [2].
[5] absorption according to the surface of the core particle [4] or [1], which has a core-shell structure coated with particulate shell of the layered double hydroxide (A) of the zeolite (B) <br/> Adhesive.
[6] The core particles and the fine particles shell and mass ratio of 1: 0.25 to 1: adsorbents according to present at 0.001 [5].
[7] As a whole, the primary average particle size is 0.1 to 300 by the particle size measurement method by electron microscopy.
adsorbents according to one having a [mu] m [6].

In the present invention, a zeolite slurry having a regular particle structure is used as a raw material, and an aqueous solution containing two or more specific metal salts is added under alkaline conditions, whereby the zeolite (B) is used as a core to form a layered composite. Hydroxide (A) is deposited on the surface.

General formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} A _{x / z} ^z- · mH ₂ O ( ₂ ) represented by (a)
Combination of trivalent metal ions and general formula [Al ₂ Li (OH) ₆ ] ^{x +} [A ⁿ⁻ _{x / n} · mH ₂ O] ^x− ·
A compound that forms a basic layer by a combination of Li (monovalent) -Al (trivalent) metal ions represented by (b) is known. M ²⁺ is Mg, Ca, Mn, Fe, Co, Ni, Cu, Z
At least one divalent metal represented by n and the like, M ³⁺ is Al, Fe, Cr, Ga, In
At least one trivalent metal typified by an equal, A ^{n-is, OH -, Cl -, Br} -, CO 3 2
⁻ , NO ₃ ²⁻ , SO ₄ ²⁻ , Fe (CN) ₆ ⁴⁻ , and at least one of n-valent ion-exchangeable anions represented by tartrate ions. The divalent to trivalent system is a non-stoichiometric compound represented by the general formula (a) (0 <x ≦ 0.4), and it is possible to synthesize compounds with various combinations and composition ratios. The outline of the crystal structure is that a base layer similar to Brucite Mg (OH) ₂ having a positive charge is formed by substituting a part of the divalent metal M ^{2+ with} the trivalent metal M ^3+. In order to maintain the properties, a layered structure composed of a negatively charged intermediate layer is adopted.

In addition, a similar layered double hydroxide can also be obtained in the Li—Al system (monovalent metal and trivalent metal) represented by the formula (b). Clays and Clay Mins
erals), Vol. 30, p180-184. Al is arranged in the Gibbsite structure and its vacancy (Va
cancy) is occupied by Li ions to form a two-dimensional layer, and an anion is incorporated between the layers to compensate for the charge. Here, layered double hydroxide (Layered Double Hydroxide:
(LDH) is a general term including hydrotalcite and hydrotalcite described below.

Hydrotalcite was originally given to the natural mineral Mg ₆ Al ₂ (OH) ₁₆ CO ₃ · 4-5H ₂ O, but many minerals with the same crystal structure were discovered and synthesized thereafter. . It is represented by the following general formula (a) or (b).

[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} [A ^n- _{x / n} · mH ₂ O] ^x- (a)
[Al ₂ Li (OH) ₆ ] ^{x +} [A ⁿ⁻ _{x / n} · mH ₂ O] ^x− (b)
Here, 0.1 ≦ x ≦ 0.4, 0 <m, n is a natural number from 1 to 4, M ²⁺ is Mg, Ca, M
n, Fe, Co, Ni, Cu, Zn, etc., at least one divalent metal represented by M ³⁺ is at least a trivalent metal represented by Al, Fe, Cr, Ga, In, etc. One type, ^An-
OH ⁻ , Cl ⁻ , Br ⁻ , CO ₃ ²⁻ , NO ₃ ²⁻ , SO ₄ ²⁻ , Fe (CN) ₆ ⁴⁻ , at least one of n-valent ion-exchangeable anions represented by tartrate ions .

In the above general formula (a), a compound in which M ²⁺ is Mg ²⁺ and M ³⁺ is Al ³⁺ is called hydrotalcite, and other compounds of the general formula (a) and general formula (b) are Commonly called hydrotalcite. These hydrotalcites and hydrotalcites have a structural unit consisting of a positively charged basic layer and an intermediate layer with an anion and crystal water that electrically neutralizes the positive, and differ in structural breakdown temperature. Some others are known to exhibit almost similar properties, have solid basicity and anion exchange ability, and exhibit specific reactions such as intercalation and regeneration reactions. These compounds are described in detail in “Smectite Research Society Bulletin” “Smectite” (Vol. 6, No. 1, P.12-26, 1996, May). Specific examples of the layered double hydroxide include stichtite, pyroaulite, leevesite, tacovitite, onesite, iowite and the like.

Zeolite (B) in the composite of the present invention has micropores 0.5 to 0.5 as defined by IUPAC.
It is a crystalline porous body having pores having a pore diameter centered at 2 nm, and is typified by aluminosilicate having a composition represented by the following general formula. More than 40 kinds of natural products and about 150 kinds of synthetic crystals have been reported.

[Wherein, M1: monovalent cation such as Na ⁺ and K ⁺ , M2: divalent cation such as Ca ²⁺ and Sr ²⁺ , m ≦ n].

Any zeolite can be used as long as it has a regular particle structure and can exchange ions of cations such as ammonium ions. However, its use is not limited. Examples of natural zeolites include the Natrolite group represented by Natrolite, Gonaldite, Eddingtonite, etc., the Analsim group represented by Analsim, Leucite, Yugawaralite, Gismondine, Poringite-K, Philippe Site-Ca, etc. Gismondine group represented by Chabazite-Ca, Erionite-Na, Hojasite-Na, etc.Chabazite group represented by Mordenite, Ferrierite-Mg, Mortenite group represented by Mutinaite, Hulandite-Ca, clinoptilolite-
Naturally produced zeolites such as the Hulandite group represented by Na, Stillebite-Ca, etc., the aluminosilicate group of unknown structure represented by Kouresite, etc., and A, L, X, Y, Na- Synthetic zeolites such as P1, ZK-5, ZSM-11, etc. are mentioned, preferably synthetic zeolites with uniform particle size, more preferably A, X, etc. with a small difference in silica / alumina mass ratio It is. If the difference in the mass ratio of silica / alumina is too large, the ion exchange capacity is insufficient, and there is a possibility that cation adsorption characteristics such as ammonium ions cannot be sufficiently exhibited.

Zeolite has a three-dimensional network structure in which all the oxygen atoms of SiO ₄ and AlO ₄ tetrahedrons share a vertex. The shape and size of the cavity existing in the center of the network structure and the hole channel connecting the cavity vary depending on the type of crystal. Among the synthetic zeolites, there is an aluminophosphate known as the same microporous crystal, which has a three-dimensional network structure that shares the apex of oxygen atoms of AlO ₄ and PO ₄ tetrahedra, and the shape of cavities and pores depending on the type of crystal -It has a porous structure with different sizes. The microporous crystals such as zeolite and aluminophosphate have unique functions such as adsorption and ion exchange as characteristics based on the structure and chemical composition of the cavities. It is used for applications such as confinement or catalyst support.

The skeleton constituent element forming the three-dimensional network structure means an element excluding elements exchangeable by ion exchange among elements constituting the zeolite. In an aluminosilicate having a network skeleton made of SiO ₄ —AlO ₄ tetrahedron, for example, a crystal in which a part of Si of SiO ₄ is substituted with Ti which is an element having the same ionic valence is Si, Al, O, And Ti
In the aluminophosphate having a network skeleton composed of AlO ₄ —PO ₄ tetrahedrons, for example, a part of Al of the AlO ₄ is Ga, Fe, or the like, which is an element having the same valence. The substituted crystal is a crystal having Ga, Fe as a skeleton constituent element together with Al, P, and O.

There is no particular limitation on the Si source, Al source, Ti source, P source, Ga source, Fe source, etc. used for the synthetic raw material. For example, in the case of SiO ₄ -AlO ₄ based synthetic zeolite, when both are mixed Are preferably used, and the Si source is preferably sodium metasilicate, colloidal silica, fumed silica, tetraethylorthosilicate, etc., and the Al source is sodium aluminate, boehmite, pseudoboehmite, aluminum isosilicate, etc. Propoxide and the like are preferable.

The exchangeable cations contained in the zeolite are not limited by those derived from raw materials or those added by ion exchange reaction. Examples of the alkali metal include lithium, sodium, potassium, rubidium, cesium, and francium. Examples of the alkaline earth metal include beryllium, magnesium, calcium, strontium, barium, and radium. Moreover, you may contain 2 or more types of metal ions.

Further, the layered double hydroxide (A) has solid basicity and anion exchange property, and exhibits a unique reaction such as a regeneration reaction in addition to the intercalation reaction. Therefore, the layered double hydroxide (
Even if A) is a pyrolyzate heat-treated at 400 ° C. or higher, the desired function can be exhibited. In that case, the thermal decomposition product of the layered double hydroxide (A) regenerates the layered structure while inserting anions between the layers in the anion-containing aqueous solution.

The ion exchange capacity of the zeolite used in the composite of the present invention is 1.0 mmol in the dry sample.
Preferably g is ¹ or more, and more preferably 3.0Mmolg ^-1 or more. If it is 1.0 mmolg ⁻¹ or less, the ability to remove cations such as ammonium ions may be significantly reduced.

The A-type zeolite (structure code LTA) used in the composite of the present invention is a cubic zeolite having a Si / Al molar ratio of 0.7 to 1.2. Since it is a zeolite with the highest Al concentration, it has the highest ion exchange capacity and can incorporate a large amount of cation species such as ammonium ions, making it suitable as the core material of the composite of the present invention.

The X-type zeolite (structure code FAU) used in the composite of the present invention is a cubic zeolite having a Si / Al molar ratio of 1.0 to 1.5. It is a sodalite cage similar to A-type zeolite, but it is a zeolite species that has a 12-membered ring super cage in addition to a 6-membered ring window, and can easily incorporate cationic species such as ammonium ions into the cage. .

In the present invention, such a zeolite having a regular particle structure is used as a core, and a layered double hydroxide is coated on the surface thereof, and the layered double hydroxide / zeolite composite itself forms a regular particle. At the same time, amphoteric ion exchanger particles are produced by utilizing the ion exchange properties of both.

Furthermore, the formation of the layered double hydroxide shell also provides an excellent advantage in the production of the layered double hydroxide / zeolite composite. That is, the particles having the shell structure are remarkably excellent in water drainage and filterability, and provide an advantage that operations such as separation from a mother liquor by decantation and filtration and washing with water can be performed within a short time, and a filter. When applied to, it exhibits excellent performance as a filter material with little pressure loss.

In the layered double hydroxide / zeolite composite of the present invention, the core particle and fine particle shell have a ratio of 1: 0.25 to 1: 0.001, most preferably 1: 0.2 to 1: 0.05. Present in a weight ratio. The layered double hydroxide constituting the shell has a fine primary particle diameter, but the shell exists in a bulky soft state as described later.

Both the zeolite having solid acidity and the layered double hydroxide having solid basicity have the advantage that they can be easily synthesized in a large amount from a solution at around room temperature and at a relatively low temperature. According to the present invention, a layered double hydroxide coating precipitates by adding two or more water-soluble metal salts while adjusting a slurry of a synthetic or naturally produced / purified zeolite to a certain alkaline condition. This is due to the discovery of the phenomenon.

The composite of the present invention has a primary average particle size of 0.1 to 30 by a particle size measurement method by electron microscopy.
It is in the range of 0 μm, in particular 1-150 μm. In terms of the impurity removing action, the particle size of the particles used has a certain preferable range, and those having the above particle diameter are excellent in the impurity removing action. In this case, the particle size is measured by the sedimentation weight method, centrifugal sedimentation light transmission method, laser diffraction / light scattering method, etc. May be indistinguishable, so observe directly with a transmission electron microscope or scanning electron microscope, find the average value of the major and minor diameters of individual particles, and obtain the average particle diameter from the lognormal distribution of each fraction based on the number .

The layered double hydroxide coating formed in the above process has a unique coating structure. That is,
This layered double hydroxide coating is hardly released in the form of fine powder (less powdering)
It is securely attached to the surface of the above-described zeolite core in a bulky state.

Next, a method for preparing a composite having a layered double hydroxide coating layer having solid basicity on the surface of zeolite having solid acidity will be described. Here, the synthesis of the layered double hydroxide on the zeolite surface by the precipitation method in the zeolite suspension will be described. The method for producing the layered double hydroxide-zeolite composite of the present invention generally comprises the following steps. That is, first, a mixed aqueous solution of divalent metal salt and trivalent metal salt or aluminum salt and lithium salt is prepared (I). Next, an alkaline aqueous solution such as a sodium hydroxide solution and the mixed aqueous solution prepared in the step (I) are simultaneously added to the zeolite-containing water little by little to produce a coprecipitated gel (II).

This is adjusted to around pH 10 suitable for the formation of layered double hydroxides, and is aged and reacted (III) under hydrothermal conditions at room temperature or at a relatively low temperature (about 40 to 200 ° C.) to produce a composite. Thus, it is possible to suppress the growth of the layered double hydroxide particles and obtain a composite.

The obtained product was filtered and washed with distilled water to obtain a dried product. The layered double hydroxide is thermally differentiated by baking the product obtained by the above production method at a temperature of 400 to 800 ° C. for several hours, and the surface coating layer can have a layered structure regeneration function. is there. Water and anionic compounds can be incorporated between the layers by restructuring the layered structure. However, 8
If pyrolysis is performed at a high temperature of 00 ° C. or higher, spinel is formed, and thus the rebuilding ability may be lost.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by these Examples. The physical properties of the layered double hydroxide / zeolite composite were evaluated as follows.
〔Evaluation item〕
<Composition>
Scanning electron microscope [manufactured by JEOL Ltd.] JSM-5800LV was used for observation at 15 kV, and connected energy dispersive X-ray analyzer [manufactured by JEOL Ltd.] JED-2
Measurement was performed using 110 to determine the composition.
<X-ray diffraction>
X-ray diffractometer [manufactured by Rigaku Denki Co., Ltd.] Using RINT2200, CuKα rays generated at 40 kV / 40 mA are used, the divergence slit angle is 1 degree, the divergence longitudinal limiting slit is 10 mm, the scattering slit is 1.25 mm, and the light receiving slit is 0 The measurement was performed under the conditions of 3 mm, scan speed of 2 degrees / minute, and sampling width of 0.02 degrees.
<Particle morphology>
Scanning electron microscope [manufactured by JEOL Ltd.] JSM-5800LV, acceleration voltage 15k
V was observed for particle morphology.
<Adsorption characteristics>
Put 0.1 g of the sample obtained in a 50 ml polyethylene centrifuge tube and add 10 mM NH.
₄ Cl aqueous solution (10 mM, 30 ml) and H ₃ PO ₄ aqueous solution (10 mM, 30 ml) were added, respectively, and the mixture was shaken at room temperature for 24 hours and allowed to stand for 1 hour.
μm), and the filtrate was analyzed by the following method.

Ammonium ion analysis: ammonia electrode (Toa Dempa Kogyo IM-
20B, ammonium elec- trode Ae-235), the ammonium ion concentration was quantified, and the amount adsorbed per gram of adsorbent was determined. Phosphate ion analysis: emission spectrometer IC
The phosphate ion concentration was quantified with P (SEIKO SP4000) to determine the amount of adsorption per gram of adsorbent. Type A zeolite (Na ₁₂ Si ₁₂ Al ₁₂ O ₄₈ / 24H ₂ O) (Zeolite A-4
Powders manufactured by Wako Pure Chemical Industries, Ltd.) and LDH (synthesized from raw materials used in Example 1) were used as reference samples.

For LDH preparation, magnesium chloride hexahydrate (MgCl ₂ · 6H ₂ O) reagent special grade Wako Pure Chemical Industries, Ltd., aluminum chloride hexahydrate (AlCl ₃ · 6H ₂ O) reagent special grade Wako Pure Chemical Industries Ltd. A company-made sodium hydroxide (NaOH) reagent grade Wako Pure Chemical Industries, Ltd. was used.

A type zeolite (synthetic zeolite A-4 powder, through 75 μm, manufactured by Wako Pure Chemical Industries, Ltd.) is used. 0.03M MgCl _{2 with} / Al = 3/1 (mol% ratio)
-25 mL of AlCl ₃ mixed aqueous solution was added dropwise at a dropping rate of 1.7 mL / min. At this time, 0.1 M NaOH was simultaneously added dropwise to keep the pH at 10. Thereafter, 60 mL of the obtained suspension was put in a fluororesin container (100 mL capacity), covered, sealed in a stainless steel container, and aged in an oven at 150 ° C. for 24 hours. The sample after the reaction was filtered, 50 ° C., 24
After drying for a time, a layered double hydroxide / zeolite composite was obtained.

FIG. 1 (a) and FIG. 1 (b) show the observation images of the starting material A-type zeolite and the resulting composite by scanning electron microscope (SEM) and the results of elemental analysis (EDS) by wavelength dispersive X-ray. 2 (a) and 2 (b), respectively. It was found that layered double hydroxide was formed on the surface of the zeolite particles. Furthermore, the X-ray diffraction pattern of the composite is shown in FIG. Mg is detected in the composite from the results of elemental analysis, and the Mg / Al ratio is L in consideration of the composition of the zeolite.
It was in good agreement with the constituent composition Mg / Al = 3/1 (mol% ratio) of DH. Further SEM
The image and X-ray diffraction pattern results also suggest that a layered double hydroxide / zeolite composite could be synthesized. As a result of the adsorption property test shown in Table 1, it was confirmed that both ammonium ions and phosphate ions that could not be formed by the A-type zeolite and LDH alone could be adsorbed.

MgCl ₂ -AlCl ₃ mixed aqueous solution described in Example 1 (compounding ratio Mg / Al = 3/1 (m
The layered double hydroxide / zeolite composite was synthesized in the same manner as in Example 1 except that the concentration of ol% ratio)) was changed to 0.1M. As a result of observation with a scanning electron microscope (see FIG. 4 (a)), it was found that a layered double hydroxide was formed on the surface of the zeolite particles because of the similar shape as in Example 1. As a result of the adsorption property test shown in Table 1, it was confirmed that both ammonium ions and phosphate ions that could not be formed by the A-type zeolite and LDH alone could be adsorbed. Further, it is suggested that the adsorption amount of phosphate ions can be controlled depending on the concentration of the MgCl ₂ -AlCl ₃ mixed aqueous solution.

The A-type zeolite described in Example 1 was changed to X-type zeolite (synthetic zeolite F-9 powder, th
A layered double hydroxide / zeolite composite was synthesized in the same manner as in Example 1 except that the composition was changed to high 75 μm, manufactured by Wako Pure Chemical Industries, Ltd. As a result of observation with a scanning electron microscope (see FIG. 5), it was found that a layered double hydroxide was formed on the surface of the zeolite particles due to the similar shape to that of Example 1. As a result of the adsorption property test shown in Table 1, it was confirmed that both ammonium ions and phosphate ions that could not be formed by the A-type zeolite and LDH alone could be adsorbed.

The present invention relates to a layered double hydroxide (LDH) in a slurry of zeolite having a regular particle structure.
By using this precipitation method, composite particles comprising a zeolite core and an LDH shell could be formed. The layered double hydroxide / zeolite composite of the present invention has an ability to adsorb both basic substances such as ammonia and acidic substances such as phosphoric acid, and is water-dissipating despite containing LDH having a small particle size. It is remarkably excellent in filterability and is suitable for adsorbents used for filters and the like.

(A) Drawing substitute SEM image of A-type zeolite, (b) EDS analysis result. (A) Drawing-substitute SEM image of A-type zeolite-LDH composite synthesized at 150 ° C. with 0.03M MgCl ₂ -AlCl ₃ mixed aqueous solution (Mg / Al = 3), (b) EDS analysis result. 2 is an X-ray diffraction pattern of type A zeolite-LDH composite of Example 1. FIG. (A) Drawing-substitute SEM image of A-type zeolite-LDH composite synthesized at 150 ° C. with 0.1M MgCl ₂ -AlCl ₃ mixed aqueous solution (Mg / Al = 3), (b) EDS analysis result. SEM image substituted for drawing of X-type zeolite-LDH composite synthesized at 150 ° C. with 0.03M MgCl ₂ -AlCl ₃ mixed aqueous solution (Mg / Al = 3).

Claims (7)

A layered double hydroxide (A), which is an adsorbent that adsorbs a harmful substance made of a ceramic porous body, wherein the ceramic porous body is a non-stoichiometric compound represented by the following general formula (a) or (b): An adsorbent comprising a layered double hydroxide / zeolite composite containing zeolite (B).
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} [A ^n- _{x / n} · mH ₂ O] ^x- (a)
[Al ₂ Li (OH) ₆ ] ^{x +} [A ⁿ⁻ _{x / n} · mH ₂ O] ^x− (b)
(Where 0.1 ≦ x ≦ 0.4, 0 <m, n is a natural number from 1 to 4, M ²⁺ is represented by Mg, Ca, Mn, Fe, Co, Ni, Cu, Zn, etc. At least one divalent metal, M ³⁺ is at least one trivalent metal represented by Al, Fe, Cr, Co, Ga, In, etc., An ⁻ is OH ⁻ , Cl ⁻ , Br ⁻ , CO ₃ ²⁻ , NO ₃ ²⁻ , SO ₄ ²⁻ , Fe (CN) ₆ ⁴⁻ , at least one of n-valent ion-exchangeable anions represented by tartrate ions. Adsorbents according to claim 1, wherein the ion exchange capacity of the zeolite (B) is characterized in that at 1.0Mmolg ^-1 or more. Adsorbents according to any one of claims 1 to 2 wherein the zeolite (B) is characterized in that it is a type A zeolite. Adsorbents according to any one of claims 1 to 2, characterized in that the zeolite (B) is an X-type zeolite. Adsorbents according to 4 or claims 1 and having a core-shell structure in which the surface of the core particles were coated with particulate shell of the layered double hydroxide (A) of the zeolite (B). The core particles and the fine particles shell and mass ratio of 1: 0.25 to 1: adsorbents according to claim 5 which is present in 0.001. Overall, adsorbents according to claim 6 in the particle diameter measurement standard method by electron microscopy are those having a primary average particle diameter of 0.1 to 300.

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