JP2005125199A - Adsorbent, method for producing the same, and water purifier using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adsorbent excellent in strength and adsorption performance and particularly suitable for use in a water purifier, a production method thereof, and a water purifier using the adsorbent.
SOLUTION: An adsorbent in which child particles having adsorption performance are immobilized on the surface of mother particles made of a thermoplastic resin, while the adsorbent is not subjected to high-temperature thermal history, maintains high adsorption performance. Also excellent in strength. Moreover, since the manufacturing method of the adsorption agent of this invention does not need to apply high temperature, it can manufacture an adsorption agent efficiently with simple equipment. Moreover, the water purifier using the adsorbent of the present invention as a filter medium can obtain safe water from which harmful substances such as heavy metals have been removed over a long period of time.
[Selection figure] None

Description

The present invention relates to an adsorbent excellent in strength and adsorption performance, particularly suitable for water purifier applications, a method for producing the same, and a water purifier using the adsorbent.

Heavy metals such as lead, iron, copper, nickel, zinc, chromium, and cadmium are eluted from underground and water pipes and may be contained in the form of ions in well water and tap water. Various studies have been made on methods for removing these.

As these heavy metal adsorbents, for example, synthetic zeolite, amorphous titanium silicate and the like are known (for example, Patent Document 1 and Patent Document 2).

In general, adsorbents such as synthetic zeolite are synthesized with microcrystals of several tens of μm or less, and in that state, the pressure loss increases when water is passed through, so that it is difficult to use as an adsorbent for water purifiers. Therefore, the adsorbent is granulated in an appropriate particle size range.

As a granulation method, a method of binding fine particles with a binder and a binder to increase the particle size is known. Examples of the binder include bentonite, diatomaceous earth, colloidal silica, celluloses, alginates, and the like. Is used (for example, Patent Document 3).

When clay minerals such as bentonite and kaolin, synthetic zeolite fine particles and water are mixed at an appropriate blending ratio and fired at a high temperature of 600 to 800 ° C., the clay mineral such as bentonite is 700.
Since it sinters in the vicinity of ° C., it plays a role of a binder of synthetic zeolite fine particles.

However, the method of heating the adsorbent together with the clay mineral at a high temperature may cause a decrease in the adsorption performance due to the collapse of the adsorbent structure.

In addition, a method using Ca type and / or Na type CMC (carboxymethylcellulose) and a method of granulating using an organic polymer emulsion or latex are also known (for example, Patent Document 4 and Patent Document 5). ).

However, when an organic substance such as CMC is used, heat treatment at a high temperature is not required, but there is a possibility that an organic compound or its additive may be eluted, and it may not be suitable as a filler for a water purifier. In addition, powdered zeolite granulated with a small amount of an organic binder, when used in a water purifier, may not have sufficient strength and may collapse into fine particles.
Japanese Patent Laid-Open No. 7-204630 JP-T 6-504714 Japanese Patent Laid-Open No. 60-14936 Japanese Patent No. 2756567 Japanese Patent Laid-Open No. 7-144913

An object of the present invention is to provide an adsorbent excellent in strength and adsorption performance, particularly suitable for water purifier applications, a method for producing the adsorbent, and a water purifier using the adsorbent.

That is, the first gist of the present invention is an adsorbent obtained by immobilizing child particles having adsorption performance on the surface of mother particles made of a thermoplastic resin.

The second gist of the present invention is a method for producing an adsorbent, in which child particles having adsorption performance are fixed to the surface of mother particles made of a thermoplastic resin by fusion bonding or pressure bonding.

  The third gist of the present invention is a water purifier using the adsorbent as a filter medium.

The adsorbent of the present invention is excellent in strength while maintaining high adsorption performance because child particles having adsorption performance are immobilized on the surface of mother particles made of a thermoplastic resin.
Moreover, since the manufacturing method of the adsorbent of this invention does not need to granulate at extremely high temperature, it can manufacture adsorbent efficiently with simpler equipment.
Moreover, the water purifier using the adsorbent of the present invention as a filter medium can obtain safe water from which harmful substances such as heavy metals have been removed over a long period of time.

The present invention will be described in detail below.
The adsorbent of the present invention is formed by immobilizing child particles having adsorption performance on the surface of mother particles made of a thermoplastic resin. Here, the type of the thermoplastic resin is not particularly limited, and polyethylene resin, polypropylene resin, polyvinyl acetate resin, polystyrene resin, polyacrylonitrile resin, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, poly Examples include methyl methacrylate resin, polyethylene terephthalate resin, polybutadiene terephthalate resin, polycarbonate resin, polyacetal resin, and nylon resin.
Among them, polyethylene resin is preferable because it has a low melting point and can be granulated at a low heating temperature.

The child particles having an adsorption performance used in the present invention include at least one of an aluminosilicate inorganic ion exchanger, a titanium silicate compound, and a calcium phosphate compound that are excellent in adsorption performance of heavy metals, especially lead. Is preferred.
In the adsorbent of the present invention, one kind of child particle may be fixed to one mother particle, or a plurality of kinds of child particles may be fixed.

Examples of the aluminosilicate inorganic ion exchanger include molecular sieve 3A, molecular sieve 4A, molecular sieve 5A, and molecular sieve 13 which are synthetic zeolites.
X, faujasite type zeolite, and mordenite type zeolite are mentioned. These synthetic zeolites have a high adsorption capacity for heavy metal ions, and in particular, the molecular sieve 5A is excellent in the adsorption of soluble lead ions.

The child particles having adsorption performance preferably have a specific surface area of 100 m ² / g or more. In particular, those having a specific surface area of 300 m ² / g or more are more preferable because they have excellent heavy metal selective adsorption performance even in the presence of competing ions such as calcium and magnesium.

Examples of calcium phosphate compounds include hydroxyapatite, tricalcium phosphate, and tetracalcium phosphate. These calcium phosphate compounds can be synthesized by reacting an aqueous phosphate solution and an aqueous calcium salt solution.

The water purifier usually requires a flow rate of about 1 to 5 L / min. For this reason, when using an adsorption agent for a water purifier, the magnitude | size which considered this flow volume is required, and the granular thing with an average particle diameter of 30-1500 micrometers is used preferably. When the average particle size is smaller than 30 μm, the filtration resistance increases and the water permeability tends to decrease. On the other hand, when the average particle size is larger than 1500 μm, the voids between the particles become large and the removal performance tends to be lowered. The average particle size of the adsorbent is 50 to 750.
The range of μm is more preferable.
The average particle size of the adsorbent here refers to the particle size of the entire adsorbent in a state in which the child particles are immobilized on the mother particles, and by sieving using a standard sieve Can be sought.

If the average particle size of the mother particles is too large, the particle size of the adsorbent becomes too large.
m or less is preferable, and 750 μm or less is more preferable. On the other hand, if the particle size is too small, it becomes difficult to immobilize the child particles on the surface.

If the average particle size of the child particles is too large, it will be difficult to fix to the surface of the mother particles, and the adsorption performance tends to be lowered. Therefore, the average particle size of the child particles is preferably 100 μm or less, and more preferably 50 μm or less. On the other hand, if the average particle size of the child particles is too small, the amount of child particles that can be immobilized with respect to the mother particles is reduced, and the performance per volume of the adsorbent tends to be reduced. Therefore, the average particle size of the child particles is preferably 5 μm or more, and more preferably 20 μm or more.

If the ratio of the volume of the mother particles to the total volume of the adsorbent is too small, the binding force for immobilizing the child particles on the surface tends to be weak. Therefore, when the volume of the mother particle is A and the volume of the child particle is B, A / (A + B) is preferably 0.25 or more, and more preferably 0.40 or more.

On the other hand, when the volume ratio of the mother particles is too large, the amount of child particles that can be immobilized on the mother particles decreases, and the performance per volume of the adsorbent tends to decrease. Therefore, A / (A + B) is 0.95.
Or less, more preferably 0.90 or less.

In addition, the volume of a mother particle and a child particle can be calculated | required with the following procedures, for example.
1. Measure the mass of the adsorbent.
2. The adsorbent is heated by high heat above the temperature at which the mother particles burn and volatilize, and the remaining mass is measured to obtain the mass of the child particles.
3. The mass of the child particles is subtracted from the mass of the adsorbent before heating to obtain the mass of the mother particles.
4). For each of the mother particles and the child particles, the volume is calculated from the density and mass.

In the conventional technology that uses a binder as an adhesive for bonding adsorbent fine particles to each other, the blending ratio of the binder that does not have adsorption performance is reduced as much as possible, so the strength after granulation tends to be insufficient. It was. On the other hand, in this invention, it becomes possible to fix | immobilize the child particle | grains of an adsorbent precisely on the surface of a mother particle, without causing a fall of intensity | strength, using a thermoplastic resin as a mother particle. Therefore, the adsorbent of the present invention has sufficient strength while maintaining sufficient adsorption performance.

The method for producing an adsorbent of the present invention is to immobilize child particles by fusion bonding or pressure bonding when immobilizing child particles having adsorption performance on the surface of mother particles made of a thermoplastic resin.
As a method for performing melt bonding, for example, a method of heating while dispersing the mother particles and the child particles in a hot air stream can be mentioned. This method is preferable because the child particles can be uniformly fixed on the surface of the mother particles. As a manufacturing apparatus of this method, model SFS-3 of Nippon Pneumatic Industry Co., Ltd. can be mentioned as an example.

When the thermoplastic resin used as the mother particles is crystalline, the heating temperature is 10
Heating at a temperature higher by -50 ° C is preferable because the adhesiveness is improved. On the other hand, when the thermoplastic resin is amorphous, it is preferably heated at a temperature 10 to 50 ° C. higher than Tg.

As a method for immobilizing the child particles by pressure bonding, for example, there is a method in which mother particles and child particles are put in a container and the container is rotated to generate centrifugal force. Specifically, a rotor is arranged inside the container, and mother particles and child particles are dispersed between the container and the rotor,
The container and the rotor are rotated in opposite directions. At this time, the cross-sectional shapes of the container and the rotor are preferably elliptical.

In this case, the rotational speed of the elliptical rotor is preferably higher than that of the container. The rotation of the container is performed in order to appropriately disperse the mother particles and the child particles, and the rotation speed is 2
It is preferably about 0 to 250 revolutions / minute. The rotation of the elliptical rotor is performed in order to apply a compressive force to each particle existing between the container and the elliptical rotor.
About ~ 5000 rotations / minute is preferable.
Since this method can repeatedly apply a compressive force, the child particles can be uniformly immobilized on the surface of the mother particles. As a manufacturing apparatus of this method, for example, theta composer of Tokuju Corporation can be cited.

In addition to this, for example, the mother particles and the child particles can be produced by putting them in a container and heating them with stirring, or heating them while shaking the containers.

The adsorbent of the present invention has a lead adsorption amount of 150 mg / g or more and a compressive strength of 1.0 N /
By setting it to mm ² or more, it is preferable because it has sufficient strength when used in a water purifier, and therefore can be imparted with good lead adsorption performance without being destroyed by water flow. In addition,
The lead adsorption amount (mg / g) refers to the amount of lead adsorbed per gram when the adsorbent is immersed in an aqueous solution containing lead for 24 hours.
Specifically, for example, an aqueous lead nitrate solution is prepared so as to have a lead concentration of 200 mg / L, and 200 ml is taken into an Erlenmeyer flask, 100 mg of adsorbent is added, shaken, and then filtered with a filter after 24 hours. The amount of lead adsorption can be determined by measuring the residual lead concentration in the filtrate water.

The compressive strength (N / mm ² ) is Hiramatsu, Oka, Kiyama: Journal of the Japan Mining Association, 81, 1024.
(1965) with reference to the method of (1965), the compressive strength; St (N / mm ² ), P; load (N), d; Particle diameter (mm)
, It is calculated from the equation of St = 2.8P / πd ² .
Compressive strength of the adsorbent is more preferably 1.3 N / mm ² or more, 1.5 N / mm ² or more is more preferable.

The water purifier using the adsorbent of the present invention as a filter medium can efficiently remove heavy metals. Drawing 1 is a sectional view showing an example of the water purifier of the present invention. The water purifier of FIG. 1 has a first septic tank 2 in which an adsorbent is disposed and a second septic tank 7 in which a porous hollow fiber membrane is disposed. A flow rate sensor 9 is disposed between the first septic tank 2 and the second septic tank 7. Raw water such as tap water enters from the inlet 6 and is purified by an adsorbent or a porous hollow fiber membrane, and then is taken out from the water outlet 11 as purified water.
In addition to the adsorbent of the present invention, the water purifier using the adsorbent of the present invention as a filter medium can be used to efficiently remove residual chlorine, trihalomethane, general organic chemicals, disinfection by-products, agricultural chemicals and the like. It is preferable to use activated carbon. Although activated carbon has a low removal capability, it also adsorbs heavy metals and contributes to a longer life of the adsorption performance of the adsorbent. Therefore, it is more preferable to use activated carbon in combination with the adsorbent of the present invention.

The activated carbon is not particularly limited as long as it has performance that meets the purpose of removing residual chlorine, trihalomethane, general organic chemicals, disinfection by-products, agricultural chemicals, etc. A fibrous or granular material can be used.

The type of activated carbon is not necessarily limited, and natural activated carbon such as coconut shell activated carbon, bone charcoal, charcoal, pitch-based, petroleum coke-based, fired activated material such as resin or rubber, or chemically activated material can be used. Since many substances having a relatively low molecular weight, such as trihalomethane, are to be removed, water vapor activated coconut shell activated carbon is most practically preferable in consideration of economy.
Furthermore, silver or the like may be added to impart antibacterial properties.

As a water purifier of the present invention, it is more preferable to use a porous membrane together with an adsorbent because solid matter such as iron rust and pathogenic organisms (general bacteria, Escherichia coli, coliforms) can be removed. As the porous membrane, a flat membrane, a hollow fiber membrane, a tubular membrane or the like can be used, but it is more preferable to use a hollow fiber membrane having a high volumetric efficiency.

Examples of the hollow fiber membrane include cellulose, polyolefin (polyethylene, polypropylene), polyvinyl alcohol, ethylene / vinyl alcohol copolymer, polyether, polymethyl methacrylate (PMMA), polysulfone, and polyacrylonitrile. A material made of various materials such as polyethylene, polyfluorinated ethylene (Teflon (registered trademark)), polycarbonate, polyester, polyamide, and aromatic polyamide can be suitably used. Above all, considering the strength and flexibility of the film, flexibility, cleanability, handleability and high chemical resistance,
Polyolefin-based hollow fiber membranes such as polyethylene and polypropylene are preferred.

Although not particularly limited, the hollow fiber has an outer diameter of 20 to 2000 μm and a pore diameter of 0.
. It is preferable that the thickness is 01 to 2 μm, the porosity is 20 to 90%, and the film thickness is 5 to 300 μm.

When using a porous membrane in the water purifier, if the other filter medium is provided in the final stage after passing water,
This is preferable because the concern about the back contamination of bacteria from the water purification outlet can be minimized.

The adsorbent and activated carbon may be arranged in any order. Also, a mixture of the two may be used. Further, in addition to activated carbon, other components such as ion exchange resin, calcium sulfite, coral sand, barley stone, Ioishi, tourmaline may be used in combination.

The adsorbent, the activated carbon, and the porous membrane may be contained in a single container or may be a combination of these contained in a plurality of containers. Further, it is preferable to further remove coarse dust in advance by using a primary filter in the above combination.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Fine particles of titanium silicate (manufactured by Engelhard, ATS powder standard) having a particle size of 10 to 30 μm and an average particle size of 20 μm as child particles, and a particle size of 100 to 750 μm as mother particles
m, thermoplastic resin polyethylene having an average particle size of 420 μm (manufactured by Nippon Unicar, PES-20,
Additive-free), using theta composer device made by Tokusu Kosaku Co., Ltd.
Pressure was applied by centrifugal force for 15 minutes to immobilize the child particles on the surface of the mother particles, and an adsorbent of 60% by volume titanium silicate and 40% by volume polyethylene was granulated. The obtained adsorbent had a particle size of 150 to 800 μm and an average particle size of 500 μm.

<Lead adsorption test>
Using the obtained adsorbent, a lead adsorption test was performed as follows.
Prepare an aqueous lead nitrate solution with a lead concentration of 200 mg / L and place it in an Erlenmeyer flask.
l was collected. Next, 100 mg of an adsorbent for water purifier was added and shaken, and after 24 hours, it was filtered with a cellulose filter having a pore size of 0.22 μm, and the residual lead concentration in the filtrate water was measured. The results are shown in Table 1.

<Water purifier water flow test>
In the water purifier having the configuration shown in FIG. 1, a resin frame in which an adsorbent laminate 4 in which 10 g of the adsorbent prepared and 40 g of activated carbon is mixed is disposed in the first water purifier 2 and a 150 mesh nylon net is pasted. 3 and 5 were installed so that the adsorbent laminate 4 would not flow out.

In the second water purification tank 7, a polyethylene porous hollow fiber membrane 8 that has been subjected to a hydrophilic treatment is fixed with a two-component polyurethane resin, one end of which is cut open, and the first water purification tank 2. A flow rate sensor 9 was installed in the middle of the water distribution pipe 12 connecting the second water purification tank 7.

Then, lead nitrate was added to the tap water, and water adjusted to a lead concentration of 50 μg / L was passed through the inlet 6 at a water flow rate of 2 L / min. The pH of the passed water was in the range of 6.6 to 7.4.
The lead concentration in the effluent at the time of 2m ³ water flow from the water passing start was measured. The results are shown in Table 1.

<Comparative Example 1>
About the granule of titanium silicate (the Engelhard company make, ATS granules) with a particle size of 150-800 micrometers and an average particle diameter of 500 micrometers, the lead adsorption test and the water purifier water flow test were done on the same conditions as Example 1. . The results are shown in Table 1.

As can be seen from the above results, the adsorbent of the present invention is superior in that it can obtain safe water from which heavy metals such as lead are removed over a long period of time.

It is a schematic diagram which shows an example of the water purifier of this invention.

Explanation of symbols

1 Outer container 2 First water purification tank 3, 5 Resin frame (nylon net)
4 Adsorbent laminate 6 Inlet 7 Second water purification tank 8 Porous hollow fiber membrane 9 Flow rate sensor 11 Water outlet 12 Water distribution pipe

Claims (12)

An adsorbent obtained by immobilizing child particles having adsorption performance on the surface of mother particles made of a thermoplastic resin. The adsorbent according to claim 1, wherein the child particles include at least one of an aluminosilicate inorganic ion exchanger, a titanium silicate compound, and a calcium phosphate compound.   The adsorbent according to claim 1 or 2, wherein the average particle size is 30 to 1500 µm. The adsorbent according to any one of claims 1 to 3, wherein the average particle diameter of the mother particles is 20 to 1300 µm. The average particle diameter of the said child particle is 5-100 micrometers, Adsorbent as described in any one of Claims 1-4. When the volume of the mother particle is A and the volume of the child particle is B, 0.25 ≦ A / (A + B)
≦ 0.95 The adsorbent according to any one of claims 1 to 5. A method for producing an adsorbent, wherein child particles having adsorption performance are fixed on the surface of mother particles made of a thermoplastic resin by fusion bonding or pressure bonding. The method for producing an adsorbent according to claim 7, wherein the surface of the mother particle is melted by heating to a temperature 10 to 50 ° C higher than the melting point or Tg of the mother particle. The method for producing an adsorbent according to claim 8, wherein the mother particles and the child particles are heated while being dispersed in a hot air stream. A rotor is disposed inside the container, the mother particles and the child particles are dispersed between the container and the rotor, and the container and the rotor are rotated in opposite directions to repeatedly apply a compressive force. A method for producing the adsorbent according to claim 7.   The method for producing an adsorbent according to claim 10, wherein the rotor is rotated at a higher speed than the container.   A water purifier using the adsorbent according to any one of claims 1 to 6 as a filter medium.

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