JP4157946B2 - Metal hydroxide / zeolite composite and adsorbent comprising the same - Google Patents

Description

The present invention relates to a metal hydroxide / zeolite composite having a coating structure of a core made of zeolite and a shell made of metal hydroxide, 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, not only the removal of harmful anions such as arsenic and fluorine, which are problematic in drinking water, but also the need to remove both ammonia and phosphate ions at the same time, for example, in the conservation of water quality in lakes and rivers, etc. Therefore, there is a strong demand for the development of an adsorbent having amphoteric adsorption ability.

That is, in recent years, acidic gases such as H ₂ S, CO ₂ , mercaptans, basic gases such as NH ₃ , amines and water quality, and ammonium ions, phosphate ions, and arsenate ions for purification are used simultaneously for the purpose of environmental purification and deodorization. Development of an adsorbent having a composite adsorption function such as removal is required.

The present invention has been made in view of such problems, and comprises a metal hydroxide and a basic substance having a high adsorption ability for acidic substances and anions, and a zeolite having a high adsorption ability for cations. A composite particle and a method for producing the same are provided, and the metal hydroxide /
An object is to provide an adsorbent comprising a zeolite composite.

As a result of intensive studies to improve the above-mentioned problems, the present inventors have synthesized the composite particles composed of a zeolite that adsorbs a large amount of a basic substance and a metal hydroxide that strongly adsorbs an acidic substance. Has been found to be able to be solved, and the present invention has been completed.

That is, the present invention has been solved by adopting the configurations shown in the following [1] to [ 8 ].
[1] At least one of Cu, Au, Mg, Ca, Zn, Sr, Cd, Ba, Al, Ti, Ga, In, Tl, Pb, V, Bi, Cr, Mn, Fe, Co, Ni A layered double hydroxide / zeolite composite comprising the metal-containing metal hydroxide (A) and zeolite (B).
[2] The metal hydroxide (A) is aluminum hydroxide, magnesium hydroxide, iron (II) hydroxide, iron oxide (III) oxide, or iron (III) hydroxide. The metal hydroxide / zeolite composite according to [1].
[3] The metal hydroxide / zeolite composite as described in [1] or [2], wherein the zeolite (B) has an ion exchange capacity of 1.0 mMolg ⁻¹ or more.
[4] The metal hydroxide / zeolite composite according to any one of [1] to [3], wherein the zeolite (B) is an A-type zeolite or an X-type zeolite.
[5] The metal hydroxide / electrode according to any one of [1] to [4], which has a core-shell structure in which the surface of the zeolite (B) is coated with a metal hydroxide (A). Zeolite composite.
[6] The core particles and the fine particles shell and mass ratio of 1: 0.25 to 1: metal hydroxide / zeolite composite according to that exist (5) 0.001.
[ 7 ] In the metal hydroxide / zeolite composite according to any one of [1] to [6],
Its primary average particle size is 0.1 to 300 μm (by electron particle size measurement method)
A metal hydroxide / zeolite composite characterized by being.

[8] Before SL [1] to adsorbent as a component of the metal hydroxide / zeolite composite according to any one of [7].

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 the core and the metal water is added. Oxide (A) is deposited on the surface.

The metal hydroxide used in the composite of the present invention is neutralized with an alkali at a relatively low temperature,
It is a substance that can be easily synthesized by precipitation from a supersaturated aqueous solution or hydrolysis of a metal alkoxide. Specifically, copper hydroxide (II), gold hydroxide (III), magnesium hydroxide, calcium hydroxide (II), zinc hydroxide, strontium hydroxide, cadmium hydroxide, barium hydroxide, gibbsite α-Al (OH) ₃ , Bayerite β-Al (OH) ₃ , boehmite α
-AlO (OH), aluminum hydroxide represented by diaspore β-AlO (OH),
Titanium oxide hydrate, gallium hydroxide (III), indium (III) hydroxide, thallium hydroxide (I), thallium hydroxide (III), lead hydroxide (II), vanadium hydroxide (III), bismuth oxide Hydrate, manganese hydroxide (II), manganese oxide hydroxide (III), iron hydroxide (II), goethite α-FeO (OH), akaganeite β-FeO (OH), lipid crocite γ
-FeO (OH), iron oxide (III) oxide represented by limonite δ-FeO (OH),
Examples thereof include amorphous iron hydroxides such as iron (III) hydroxide and Schwertmannite, cobalt hydroxide, nickel hydroxide, and cobalt oxide hydroxide (III). Of these, aluminum hydroxide, magnesium hydroxide, iron hydroxide (II), iron oxide hydroxide (III) are particularly preferable.
Iron hydroxide (III).

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.

〔式中，Ｍ１: Ｎａ^＋,Ｋ^＋等の１価陽イオン、Ｍ２: Ｃａ^２＋, Ｓｒ^２＋等の２価陽イ
オン、ｍ≦ｎ〕。

[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 zeolite include the Natrolite group represented by Natrolite, Gonaldite, Eddingtonite, etc., the Analsim group represented by Analsim, Leucite, Yugawara Light, etc.
Gismondine Group, Chabazite-Ca, Elionite-Na, Hojasite-Na, represented by Gismondine, Poringite-K, Philipsite-Ca, etc.
Chabazite group represented by mordenite, mordenite, ferrierite-Mg, mordenite group represented by mutinaite, etc. Zeolite of each group produced naturally such as aluminosilicate group with unknown structure represented by group, koresite, etc., and A, L, X, Y, Na-P1, ZK-5, ZSM-
11. Synthetic zeolite represented by ZSM-5, etc. are preferable, however, it is preferably a synthetic zeolite having a uniform particle size, and more preferably a silica / alumina mass ratio difference is small.
, X, etc. 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, 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.

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 having the highest Al concentration, it has the highest ion exchange capacity, and it is suitable as the core material of the present invention because it can incorporate a large amount of cationic species such as ammonium ions.

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 metal hydroxide is coated on the surface thereof, and the metal hydroxide / zeolite complex itself forms regular particles, The amphoteric ion exchanger particles are produced by utilizing both ion exchange properties.

Furthermore, the formation of a metal hydroxide shell also provides excellent advantages in terms of producing metal hydroxide / zeolite composites. 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 metal hydroxide / zeolite composite of the present invention, the core particle and the fine particle shell are 1
: 0.25 to 1: 0.001, most preferably present in a weight ratio of 1: 0.2 to 1: 0.05. The metal hydroxide constituting the shell has a fine primary particle diameter, but the shell exists in a bulky soft state as described later.

Both zeolites having solid acidity and metal hydroxides having solid basicity have an advantage that they can be easily synthesized in a large amount from a solution at around room temperature and at a relatively low temperature. The present invention is a phenomenon in which deposition of a metal hydroxide coating occurs by adding at least one water-soluble metal salt while adjusting a slurry of a synthetic or naturally produced / purified zeolite to a certain alkaline condition. This is due to the finding.

The composite of the present invention has a primary average particle size of 0.1 to 300 in a particle measurement method by electron microscopy.
It is in the range of μm, especially 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 metal hydroxide coating formed in the above process has a unique coating structure. That is, the metal hydroxide coating is hardly released in a fine powder state (small powder formation) and 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 solid basic metal hydroxide coating layer on the surface of solid acidic zeolite will be described. First, the metal hydroxide coating synthesis on the zeolite surface by the precipitation method in a zeolite suspension will be described. The method for producing a metal hydroxide-zeolite composite of the present invention generally comprises the following steps. That is,
First, at least one metal salt aqueous solution (a), an alkaline aqueous solution (b) such as a sodium hydroxide solution, and zeolite particle-dispersed water (c) are prepared in advance (I). Next, the metal hydroxide gel is precipitated on the zeolite surface by adding a small amount of the metal salt aqueous solution (a) and the alkaline aqueous solution (b) to the dispersed water (c) of the zeolite particles in the reaction vessel (II).

Moreover, when a metal salt aqueous solution is heated and hydrolyzed, a metal hydroxide or a metal oxide hydrate and an acid are generated. Along with this, the liquid temperature rises, the acid vapor is released from the liquid phase, and nuclei of metal hydroxide or metal oxide hydrate are formed. If the solution is heated to a temperature higher than 60 ° C. and lower than the boiling point at this stage, the separation of hydrochloric acid vapor from the liquid phase becomes larger, the reaction proceeds rapidly in equilibrium, and the formation of new nuclei is suppressed. Thus, an environment in which the nuclei of the metal hydroxide that has already been generated easily grows. On the other hand, at a temperature higher than the boiling point, it is necessary to use a pressurizing device such as an autoclave and a closed container, and problems such as degassing treatment remain, so it is preferable to perform hydrolysis at normal pressure.

A metal is prepared by adjusting the above product to an alkali suitable for the production of a metal hydroxide and aging and reacting at room temperature or a relatively low temperature (about 40 to 200 ° C.) under hydrothermal conditions. It is possible to obtain a composite that suppresses the growth of hydroxide particles and has a high specific surface area and excellent double adsorption ability.

The obtained product is filtered and washed with distilled water, and the product is fired at a temperature of 400 to 800 ° C. for several hours to change the metal hydroxide into a metal oxide, thereby stabilizing the particles. It is possible to improve.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by these Examples. In addition, the particle form of the metal hydroxide / zeolite composite was determined by using a field emission scanning electron microscope FE-SEM [HITACHI S-5000 to accelerate voltage 10 k.
Observation was performed at V.

For the preparation of metal hydroxide / zeolite composites, aluminum chloride (III) hexahydrate (A
lCl ₃ · 6H ₂ O) Reagent special grade Wako Pure Chemical Industries, Ltd., iron (III) chloride hexahydrate (FeC
l ₃ · 6H ₂ O) guaranteed reagent manufactured by Wako Pure Chemical Industries, Ltd., sodium hydroxide (NaOH) special grade manufactured by Wako Pure Chemical Industries, Ltd., A-type zeolite (synthetic zeolite A-4 powder, thr
Ough 75 μm, manufactured by Wako Pure Chemical Industries, Ltd.) was used.

A-type zeolite: distilled water = 1.0 g: 0.
25 mL of 02M AlCl ₂ aqueous solution was added dropwise at a dropping rate of 1.7 mL / min. At this time, pH 10
In order to maintain the same, 0.1 M NaOH was simultaneously added dropwise. 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 100 ° C. for 24 hours. The sample after the reaction is filtered, 50 ° C., 2
Drying for 4 hours gave a metal hydroxide / zeolite composite. This metal hydroxide was a low crystalline pseudo boehmite (α-AlO (OH)) and covered the entire surface of the A-type zeolite on the cube. Scanning electron microscope (SEM) of starting material A-type zeolite and the resulting composite
1), the observed images are shown in FIGS. 1, 2a and 2b.

A metal oxide / zeolite composite was synthesized in the same manner as in Example 1 except that the AlCl ₃ aqueous solution described in Example 1 was changed to an FeCl ₃ aqueous solution. Observation with scanning electron microscope (Fig. 3a,
3b), it was found that a metal hydroxide shell was formed on the surface of the zeolite particles from the similar shape to that of Example 1. This metal hydroxide was goethite in the form of elongated particles (α-FeO (OH)) and covered the surface of the A-type zeolite on the cube.

According to the present invention, composite particles having a core-shell structure comprising a zeolite core and a metal hydroxide shell are obtained. This composite particle is composed of zeolite that adsorbs basic substances such as NH ₃ and amines and metal hydroxide that adsorbs acidic substances such as phosphoric acid, arsenic acid, and carbonic acid, and therefore has the ability to adsorb both substances. Therefore, it is suitable as an adsorbent for environmental pollutants such as water or soil. Further, it can be widely used in this field or other fields such as cosmetics by taking advantage of the combined function.

SEM image of A-type zeolite in place of drawing. SEM images [(a) × 10000, (b) × 40000) of a metal hydroxide / zeolite composite synthesized at 100 ° C. with a 0.02M AlCl ₃ mixed aqueous solution. Drawing SEM images [(a) × 15000, (b) × 70000] of a metal hydroxide / zeolite composite synthesized at 100 ° C. with a 0.02M FeCl ₃ mixed aqueous solution.

Claims (8)

Contain at least one metal among Cu, Au, Mg, Ca, Zn, Sr, Cd, Ba, Al, Ti, Ga, In, Tl, Pb, V, Bi, Cr, Mn, Fe, Co, Ni A metal hydroxide / zeolite composite comprising the metal hydroxide (A) and zeolite (B). The metal hydroxide (A) is aluminum hydroxide, magnesium hydroxide, iron hydroxide ( II), iron oxide hydroxide (III), or iron hydroxide (III). Metal hydroxide / zeolite composite as described in 1. The metal hydroxide / zeolite composite according to claim 1 or 2, wherein the zeolite (B) has an ion exchange capacity of 1.0 mMolg ^-1 or more.     The metal hydroxide / zeolite composite according to any one of claims 1 to 3, wherein the zeolite (B) is an A-type zeolite or an X-type zeolite.     5. The metal hydroxide according to claim 1, which has a core-shell structure in which the surface of the core particle of the zeolite (B) is covered with a fine particle shell of the metal hydroxide (A). / Zeolite complex. 6. The metal hydroxide / zeolite composite according to claim 5, wherein the core particles and the fine particle shell are present in a mass ratio of 1: 0.25 to 1: 0.001. The metal hydroxide / zeolite composite according to any one of claims 1 to 6, wherein
The primary average particle size is 0.1 to 300 μm (by particle size measurement method by electron microscopy).
A metal hydroxide / zeolite composite characterized by the above. An adsorbent comprising the metal hydroxide / zeolite composite according to any one of claims 1 to 7 as a component.

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