JP6965117B2 - Metal ion adsorbent and composite adsorbent using it - Google Patents

Description

The present invention relates to a metal ion adsorbent and a composite adsorbent using the same, and more particularly, a metal ion adsorbent having improved metal ion adsorption performance by using an alkali metal titanate, and further, a composite adsorbent using the same. Regarding.

Activated carbon can adsorb various molecules due to its developed porosity. Moreover, since the raw material itself is inexpensive, it is widely used regardless of whether it is for industrial use or household use. The target of adsorption of activated carbon mainly depends on the pore diameter and volume of the surface of activated carbon, the distribution of pores, and the like. Therefore, the carbon source as a raw material and the conditions for firing and activation are appropriately selected according to the purpose.

However, since activated carbon is generally not suitable for adsorbing metal ions, it is common to use activated carbon in combination with other adsorbents. Specifically, a combination of activated carbon with an organic adsorbent such as an ion exchange resin, or an inorganic adsorbent such as hydroxyapatite or zeolite has been proposed. Since the inorganic adsorbent has an ion exchange action, it is effective in removing heavy metal ions from water. In particular, the removal of heavy metals is an urgent issue in securing safe drinking water due to the increasing demand for water and the deterioration of the environment due to the increase in population.

When an ion exchange resin is used for adsorbing metal ions, the ion exchange resin is expensive and bulky. Therefore, the product cost cannot be reduced and miniaturization is difficult. In the case of hydroxyapatite, the ion exchange capacity is insufficient. Therefore, the use of zeolite having an excellent metal ion adsorption rate has been studied.

For example, a heavy metal ion adsorbent in which a zeolite in which 60 mol% or more of the exchangeable total cation amount is replaced with calcium ions and / or magnesium ions is attached to the surface of activated carbon using a binder has been proposed (Patented). Reference 1). Further, from a composite powder obtained by adhering a plastic powder to a non-crystalline titanosilicate-based compound or a fine particle compound composed of A-type or X-type zeolite so as to be 3 to 20% by weight, and a powdery, granular or fibrous material. A composite adsorbent composed of an adsorptive substance to which at least one selected plastic powder has not adhered has been proposed (see Patent Document 2).

The adsorbent using the zeolite has good metal ion adsorption performance. However, it has been pointed out that aluminum may be eluted from the zeolite contained in the adsorbent. Therefore, another adsorbent is required. Further, since the adsorbent such as zeolite is aggregated by using the resin binder, the adsorption performance is not sufficiently exhibited.

From a series of circumstances, it is difficult to realize miniaturization of the adsorbent according to the above-mentioned ion exchange resin, hydroxyapatite, and zeolite adsorbent. For example, considering that various objects can be efficiently adsorbed in a small number of installation places such as a water purifier for home use, further improvement in performance is required. Therefore, there has been a demand for an adsorbent that is effective in adsorbing new metal ions, particularly heavy metal ions, which are different from existing ion exchange resins, hydroxyapatite, and zeolite.

Based on this background, the inventors searched for a new adsorbent and found that the alkali metal titanate was good at adsorbing metal ions, and reduced the metal ion adsorption capacity of the alkali metal titanate. We have completed a new adsorbent that can be aggregated with a binder without causing it (see Patent Document 3).

International release WO2005 / 909610 Japanese Patent No. 4361489 JP-A-2015-229122

The present invention has been proposed in view of the above circumstances, and is a metal ion adsorbent in which an alkali metal titanate is aggregated with a binder as an adsorbent different from existing ion exchange resins, hydroxyapatite, and zeolite. A new metal ion adsorbent whose adsorption performance and strength have been improved by using the binder of No. 1 and a composite adsorbent and a filtration member using the same are provided.

That is, the first invention comprises mixing crystalline fine particles of an alkali metal titanoate crystal-grown by the flux method with a polyethylene resin binder having a weight corresponding to 6 to 20% by weight of the crystalline fine particles . The present invention relates to a metal ion adsorbent, which is a mixture of crystalline fine particles formed by binding the crystalline fine particles to each other by heating.

The second invention relates to the metal ion adsorbent according to the first invention, wherein the alkali metal titanate salt is a sodium titanate salt.

The third invention relates to the metal ion adsorbent according to the second invention, wherein the flux agent is sodium nitrate in the crystal growth of the sodium titanate salt.

The fourth invention relates to the metal ion adsorbent according to any one of the first to third inventions, wherein the average particle size of the crystalline fine particles is 1 to 100 μm.

A fifth invention relates to the metal ion adsorbent according to any one of the first to fourth inventions, wherein the polyethylene-based resin binder is in the form of an emulsion.

The sixth invention relates to the metal ion adsorbent according to any one of the first to fifth inventions, wherein the polyethylene-based resin binder is a polyethylene, an ethylene-α-olefin copolymer, or an ethylene-vinyl acetate copolymer. ..

A seventh invention relates to a composite adsorbent containing the crystalline fine particle mixture according to any one of the first to sixth inventions and activated carbon.

The eighth invention relates to a filtration member comprising the composite adsorbent according to the seventh invention.

According to the metal ion adsorbent according to the first invention, crystalline fine particles of an alkali metal titanoate crystal-grown by the flux method and a polyethylene-based resin having a weight corresponding to 6 to 20% by weight of the crystalline fine particles. Since it is a crystalline fine particle mixture obtained by binding and granulating the crystalline fine particles by mixing with a binder and heating , it is possible to improve the adsorption performance and strength of metal ions.

According to the metal ion adsorbent according to the second invention, in the first invention, since the alkali metal titanate salt is a sodium titanate salt, it can be produced at low cost.

According to the metal ion adsorbent according to the third invention, in the second invention, since the flux agent is sodium nitrate during crystal growth of the sodium titanate, the metal component does not become an impurity and is washed and removed by washing with water. Is possible. In addition, nitric acid can be volatilized by heating and is unlikely to become an impurity.

According to the metal ion adsorbent according to the fourth invention, in any one of the first to third inventions, since the average particle size of the crystalline fine particles is 1 to 100 μm, the time required for crystal growth is short.

According to the metal ion adsorbent according to the fifth invention, in any one of the first to fourth inventions, since the polyethylene-based resin binder is in the form of an emulsion, granulation is facilitated and the outflow of fine powder is suppressed. Can be done.

According to the metal ion adsorbent according to the sixth invention, in any one of the first to fifth inventions, the polyethylene-based resin binder is a polyethylene, an ethylene-α-olefin copolymer, or an ethylene-vinyl acetate copolymer. Therefore, the mechanical strength can be increased while having excellent adsorption performance.

According to the composite adsorbent according to the seventh invention, since it contains the crystalline fine particle mixture according to any one of the first to sixth inventions and activated carbon, it is possible to cope with a wider variety of adsorption targets.

Since the filtration member according to the eighth invention has the composite adsorbent according to the seventh invention, it can be easily applied to a water purifier.

It is a schematic process diagram explaining the production of the metal ion adsorbent of this invention. It is the schematic which shows the use example of the composite adsorbent of this invention. It is the schematic which shows the use example of the filtration member of this invention.

The metal ion adsorbent of the present invention is formed as an appropriate granular material by granulation by mixing crystalline fine particles of alkali metal titanate and a polyethylene resin binder and aggregating them. Metal ions are trapped in the crystal lattice of the alkali metal titanate. This metal ion is mainly a heavy metal ion such as lead, iron, manganese, zinc, copper and cadmium. Then, by combining another type of adsorbent with the granulated product of the crystalline fine particles of the alkali metal titanate, the composite adsorbent can be finished in a wider range of adsorption targets.

The alkali metal titanoate salt is produced by mixing and heating an alkali metal salt such as sodium carbonate and titanium oxide. In this case, in particular, crystal growth is performed by the flux method. The advantage of the flux method is that the melting point of the raw material compound at the time of melting can be lowered by adding the flux agent described later together. Therefore, the energy efficiency required for production is improved. In addition, the process and time from the raw material compound to the final product can be shortened. Since the metal ion adsorbent is, so to speak, a filter material, it is required in a large amount. From this, the flux method that can be mass-produced with high production efficiency is extremely effective.

The alkali metal titanate salt can be any of sodium salt, potassium salt, lithium salt and the like. In this case, a sodium titanate salt that can be produced at low cost is preferable in consideration of the results of the trial production example of metal ion adsorption described later and the raw material cost. The alkali metal titanate salt is a trititanate, mainly a sodium trititanate salt. In addition, crystal forms such as dititanate and tetratitanate are also included. In the case of the flux method, since the reaction takes a short time at a low melting point, it is considered that a plurality of crystal types are likely to occur.

Sodium carbonate, sodium chloride, potassium carbonate, potassium chloride and the like are used as the raw material alkali metal salt for growing crystals of the alkali metal titanoate. Then, titanium oxide is added. Titanium oxide is preferably anatase type. Titanium oxide is preferably in powder form from the viewpoint of workability.

Then, sodium nitrate is used as a flux agent for the alkali metal salt and titanium oxide. Sodium nitrate is the same metal component as the above-mentioned alkali metal salt sodium carbonate, does not become an impurity, and can be washed and removed by washing with water. In addition, the nitric acid content of sodium nitrate is volatile by heating and is unlikely to become an impurity. Which compound is used as the flux agent is selected in consideration of conditions such as the type of the raw material compound and the control of the melting temperature.

The crystalline fine particles of the alkali metal titanoate crystal-grown by the flux method become finer particles than the particles produced by normal crystal growth. In this case, the average particle size of the crystalline fine particles is 1 to 100 μm. This is a phenomenon that often occurs in the flux method. Although the flux method has the advantages of low melting point and short time, the time required for crystal growth is shortened by that amount, and it is not easy to grow large crystals.

As described above, if the crystalline fine particles are left as they are, they may take a long time to precipitate or may flow out into running water when incorporated into the filtration member. Therefore, it would be convenient if the crystalline fine particles could be agglomerated into larger particles while suppressing a decrease in the metal ion adsorption capacity of the alkali metal titanate. Therefore, in order to bind the crystalline fine particles together for granulation, a polyethylene resin binder having a weight corresponding to 6 to 20% by weight of the crystalline fine particles of the alkali metal titanate is blended.

Polyethylene-based resin binders are convenient because they are inexpensive and are used in large quantities. Polyethylene-based resins (thermoplastic resins) have better toughness than thermosetting resins and are easy to heat-process. By using a polyethylene-based resin as a binder, the material strength, particularly elasticity and ductility, is increased, the material is less likely to collapse or detach due to water pressure, and the outflow of fine particles can be prevented. In particular, polyethylene, an ethylene-α-olefin copolymer, or an ethylene-vinyl acetate copolymer is preferably used as the polyethylene-based resin binder.

Subsequently, the manufacturing process of the metal ion adsorbent will be described with reference to the schematic process diagram of FIG. First, alkali metal salts (Na ₂ CO ₃ etc.) and titanium oxide (TiO ₂ etc.), which are raw materials, are weighed and prepared in predetermined amounts. A flux agent (NaNO _3, etc.) is also added here after a predetermined measurement. These three types of compounds are heated to about 500 ° C. to 600 ° C. to promote crystal growth. In this way, first, crystalline fine particles of the alkali metal titanate can be obtained. When growing crystals of an alkali metal titanate without adding a flux agent, heating at 1000 ° C. or higher is usually required.

The crystalline fine particles of the alkali metal titanate salt are appropriately washed with water, and a polyethylene resin binder is added. It is preferable that the polyethylene-based resin binder is in the form of an emulsion because it easily blends with the crystalline fine particles and is less likely to cause unevenness, so that granulation can be easily performed. Here, the crystalline fine particles aggregate to form granulated products through heat drying. Then, it is classified according to the particle size through sieving with a cyclone or a sieve having a desired opening. In this way, a metal ion adsorbent which is a granulated product of crystalline fine particles of an alkali metal titanate is completed. When the polyethylene-based resin binder is made of polyethylene, an ethylene-α-olefin copolymer, or an ethylene-vinyl acetate copolymer, it is preferable because it has appropriate flexibility, is not easily damaged by impact or the like, and is less likely to cause fine powder to flow out.

The metal ion adsorbents described in detail so far are effective in adsorbing heavy metal ions such as lead, iron, manganese, zinc, copper and cadmium, as disclosed in the prototype examples described later. Therefore, the metal ion adsorbent and activated carbon effective for adsorbing various organic compounds are further mixed to form a composite adsorbent. Activated carbon can respond to various adsorption targets by controlling its pores. For example, activated carbon disclosed in Japanese Patent Application Laid-Open No. 2013-220413 is suitable for adsorbing trihalomethanes.

As can be seen from the schematic view of FIG. 2, the metal ion adsorbent Am and the activated carbon C are mixed in appropriate amounts to obtain the composite adsorbent M. For example, the composite adsorbent M is housed in the filtration member 10 of FIG. 2A. Fine permeation holes 16 are formed on the surface portion 15 of the container body 11 of the filtration member 10. A water guide portion 14 is provided inside the container body 11. As shown in FIG. 2B, the container body 11 is covered with the lid portion 12 and the composite adsorbent M is completely contained.

In this way, the filtration member 10 having the composite adsorbent M is completed. The water to be treated (water before treatment) penetrates into the inside of the filtration member 10 through the through hole 16 of the surface portion 15. Then, the water to be treated is adsorbed and filtered by coming into contact with the composite adsorbent M. Then, the water to be treated (water after treatment) after filtration flows out from the water guiding portion 14 to the outside of the filtration member 10.

A water purifier is mentioned as a main use of the filtration member. As shown in the schematic view of FIG. 3, the water purifier 20 is attached to the tip of the faucet 25 of the water supply. A filtration chamber 23 is provided on the side of the water switching portion 21. The filtration member 10 is housed in the filtration chamber 23. In the figure, reference numeral 22 is a switching lever, and 24 is a fixed lid. Various members such as a hollow fiber filter and a flow meter are also attached to the water purifier 20 as needed. Of course, since the illustration is an example of the filtration member, other forms can be freely used. Furthermore, it is also possible to make a large-scale processing device assuming use in a stationary type or a factory. In particular, it is effective for water treatment of drinking water such as tap water.

[Raw materials used]
Sodium titanate was used as the alkali metal titanate. The sodium titanate salt is prepared by mixing sodium carbonate (manufactured by Daito Chemical Co., Ltd.), titanium oxide (manufactured by Teika Co., Ltd.), and sodium nitrate (manufactured by Ube Kosan Co., Ltd.) as a flux agent, and then filling the bowl with the lid. The mixture was sealed and heated at 600 ° C. to grow crystals. Then, crystalline fine particles of sodium titanate were prepared through appropriate washing with water (the preparation is sodium titanate crystallized by the flux method). The crystalline fine particles were measured by a laser diffraction / scattering type particle size / particle size distribution measuring device (manufactured by Shimadzu Corporation: SALD-3000S). The average particle size was defined as the particle size at an integrated value of 50% in the particle size distribution obtained by the laser diffraction / scattering method using the same measuring device.

The following types of polyethylene resin binders were used.
Made by Mitsui Chemicals, Inc .: Chemipearl (registered trademark) M200 (concentration 40%) (low density polyethylene)
{Hereafter, it will be referred to as E1. }
Mitsui Chemicals, Inc .: Chemipal A100 (ethylene-α-olefin copolymer)
{Hereafter, it will be referred to as E2. }
Mitsui Chemicals, Inc .: Chemipal V200 (ethylene vinyl acetate copolymer)
{Hereafter, it will be referred to as E3. }
Mitsui Chemicals, Inc .: Miberon (registered trademark) (high molecular weight polyethylene)
{Hereafter, it will be referred to as E4. }
Sumitomo Seika Chemical Co., Ltd .: Frosen (registered trademark) UF-1.5 (fine powdered polyethylene)
{Hereafter, it will be referred to as E5. }
Subsequently, the following types were used as other binders.
Wako Pure Chemical Industries, Ltd .: Water glass (solute concentration 52%)
{Hereafter, it is referred to as C1. }
Made by Nissan Chemical Industries, Ltd .: Snowtech O (particle size 10 to 20 nm, pH 2 to 4) (coloidal silica)
{Hereafter, it will be referred to as C2. }
Made by Asahi Glass Co., Ltd .: FLUON (registered trademark) (polytetrafluoroethylene)
{Hereafter, it will be referred to as C3. }
Made by TAKI CHEMICAL CO., LTD .: First aluminum phosphate
{Hereafter, it will be referred to as C4. }
Made by Nippon Synthetic Chemical Industry Co., Ltd .: Gosenol (registered trademark) N-300 (polyvinyl alcohol)
{Hereafter, it will be referred to as C5. }

In preparing the composite adsorbent, the metal ion adsorbent and activated carbon of each prototype were combined. As this activated carbon, CN5100S (particle size 0.15 to 0.30 μm) manufactured by Futamura Chemical Co., Ltd .: granular activated carbon was used.

[Preparation of metal ion adsorbent]
As shown in each of the prototypes disclosed in Tables 1 to 4, a metal ion adsorbent was prepared by mixing sodium titanate crystals with various binders. Then, the strength index of the adsorbent of each prototype and the adsorption rate for each metal ion were measured.

[Creation of composite adsorbent]
Further, as shown in Tables 5 to 8, 10 parts of the adsorbent of each prototype and 90 parts of activated carbon were mixed to form a composite adsorbent, and the initial amount of fine powder and the removal performance of soluble lead of each prototype were measured.

[Prototype example 1]
0.5 kg of an emulsion of low-density polyethylene (E1) was added to 3.0 kg of sodium titanate for growing crystals by the flux method, and the mixture was uniformly mixed. The mixture was heat dried at 120 ° C. for 4 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 1). In Prototype Example 1, 6.7% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Prototype example 2]
To 3.0 kg of sodium titanate grown by the flux method, 0.5 kg of an emulsion of an ethylene-α-olefin copolymer (E2) was added and mixed uniformly. The mixture was heat dried at 120 ° C. for 4 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 2). In Prototype Example 2, 6.7% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Prototype example 3]
0.5 kg of an emulsion of ethylene-vinyl acetate copolymer (E3) was added to 3.0 kg of sodium titanate for growing crystals by the flux method, and the mixture was uniformly mixed. The mixture was heat dried at 120 ° C. for 4 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 3). In Prototype Example 3, 6.7% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Prototype example 4]
0.6 kg of an emulsion of ethylene-vinyl acetate copolymer (E3) was added to 3.0 kg of sodium titanate for growing crystals by the flux method, and the mixture was uniformly mixed. The mixture was heat dried at 120 ° C. for 4 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 4). In Prototype Example 4, 8.0% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Prototype Example 5]
0.8 kg of an emulsion of ethylene-vinyl acetate copolymer (E3) was added to 3.0 kg of sodium titanate for growing crystals by the flux method, and the mixture was uniformly mixed. The mixture was heat dried at 120 ° C. for 4 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 5). In Prototype Example 5, 10.6% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Prototype example 6]
0.5 kg of high molecular weight polyethylene (E4) powder was added to 3.0 kg of sodium titanate for growing crystals by the flux method, and the mixture was uniformly mixed. The mixture was heat dried at 120 ° C. for 4 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 6). In Prototype Example 6, 16.7% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Prototype example 7]
To 3.0 kg of sodium titanate for growing crystals by the flux method, 0.5 kg of fine powdered polyethylene (E5) powder was added and mixed uniformly. The mixture was heat dried at 120 ° C. for 4 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 7). In Prototype Example 7, 16.7% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Prototype Example 8]
20 g of water glass (C1) was dissolved in 100 mL of ion-exchanged water to prepare a water glass solution. 100 mL of this water glass solution was sprayed onto 60 g of sodium titanate salt grown by the flux method and mixed uniformly. The mixture was heat dried at 150 ° C. for 2 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 8). In Prototype Example 8, 18.5% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Prototype example 9]
60 g of sodium titanate salt grown by the flux method was sprayed with 100 mL of an emulsion of colloidal silica (C2) (diluted to 20% solute) and mixed uniformly. The mixture was heat dried at 150 ° C. for 2 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 9). In Prototype 9, 20.0% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Prototype Example 10]
12.5 mL of an emulsion of polytetrafluoroethylene (C3) (solute concentration 60%) was sprayed onto 60 g of sodium titanate salt grown by the flux method and mixed uniformly. The mixture was heat dried at 150 ° C. for 2 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 10). In Prototype Example 10, 12.5% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Prototype Example 11]
50 mL of a solution of primary aluminum phosphate (C4) (solute concentration 41.5%) was sprayed onto 60 g of sodium titanate salt grown by the flux method and mixed uniformly. The mixture was heat dried at 150 ° C. for 2 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 11). In Prototype Example 11, 25.0% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Prototype Example 12]
To 3.0 kg of sodium titanate for growing crystals by the flux method, 0.4 kg of polyvinyl alcohol (C5) powder was added and mixed uniformly. The mixture was heat dried at 120 ° C. for 4 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 12). In Prototype 12, 13.0% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Prototype Example 13]
To 3.0 kg of sodium titanate grown by the flux method, 0.3 kg of an emulsion of ethylene-vinyl acetate copolymer (E3) was added and mixed uniformly. The mixture was heat dried at 120 ° C. for 4 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 13). In Prototype Example 13, 4.0% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Prototype Example 14]
To 3.0 kg of sodium titanate grown by the flux method, 0.4 kg of an emulsion of ethylene-vinyl acetate copolymer (E3) was added and mixed uniformly. The mixture was heat dried at 120 ° C. for 4 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 14). In Prototype 14, 5.0% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Prototype Example 15]
To 3.0 kg of sodium titanate grown by the flux method, 1.6 kg of an emulsion of ethylene-vinyl acetate copolymer (E3) was added and mixed uniformly. The mixture was heat dried at 120 ° C. for 4 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 15). In Prototype Example 15, 21.6% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Prototype Example 16]
To 3.0 kg of sodium titanate for growing crystals by the flux method, 0.15 kg of fine powdered polyethylene (E5) powder was added and mixed uniformly. The mixture was heat dried at 120 ° C. for 4 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 16). In Prototype Example 16, 5.0% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Prototype example 17]
0.66 kg of fine powdered polyethylene (E5) powder was added to 3.0 kg of sodium titanate for growing crystals by the flux method, and the mixture was uniformly mixed. The mixture was heat dried at 120 ° C. for 4 hours. Then, it was passed through a sieve of 80/300 mesh (upper mesh opening 0.180 mm, lower mesh opening 0.045 mm), and the mixture remaining on the sieve was used as a metal ion adsorbent (Prototype Example 17). In Prototype Example 17, 22.0% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Measurement of intensity index]
A 100 cc stainless steel pot was filled with five iron balls having a diameter of 5 mm and 5.0 g of each prototype, and vibrated in a fine powder crusher for 4 minutes. The crushed sample was taken out, sieved with a mesh of 330 mesh (opening 0.045 mm), and the strength index was calculated from the ratio of the remaining amount on the sieve to the total amount of the sample.
Intensity index (%) = remaining amount on sieve (g) / total amount of sieved sample (g) x 100

[Metal ion adsorption test]
Six kinds of metal salts of Pb, Fe, Mn, Zn, Cu, and Cd were prepared as measurement targets. Each metal ion concentration was set to 100 μg / L and dissolved in ion-exchanged water to prepare a test stock solution containing 6 kinds of metal ions. Thermo Fisher Scientific Co., Ltd., atomic absorption spectrophotometer (iCE3000 series) was used to measure the amount of metal ions in water.

100 mL of the test stock solution was dispensed into a 300 mL Erlenmeyer flask, and 0.1 g of the metal ion adsorbent of the prototype was added. The whole Erlenmeyer flask was shaken for 24 hours and adsorbed. After the shaking was stopped, the mixture was allowed to stand for 1 hour, and the supernatant (supernatant) was separated and filtered through a disposable filter unit DISMIC (pore diameter 0.2 μm) manufactured by Toyo Filter Paper Co., Ltd. The filtrate was measured by the atomic absorption spectrophotometer.

The metal ion adsorption rate (Ads) (%) was calculated for each of the six metal ions in one prototype example and a comparative example as follows.
Adsorption rate Adds (%) = [1-{(test stock solution concentration Ds-post-adsorption concentration Da) / test stock solution concentration Ds}] x 100

For each prototype, Tables 1 to 4 show the type and form of the binder, the ratio of the binder weight to the sodium titanate weight (% by weight), the strength index, and the adsorption rate (%) of each metal ion of the metal ion adsorbent. Indicated.

[Creation of filtration member]
As described above, the inventor has clarified that the metal ion adsorbent disclosed in the prototype example exhibits good adsorption ability of various metal ions. Based on this result, a composite adsorbent was prepared by combining sodium titanate, which is effective for adsorbing metal ions, and activated carbon, which is often used as an existing adsorbent. Assuming that the composite adsorbent will be used in an actual water purifier, the quality of the composite adsorbent is determined by the generation of fine powder due to water flow and the adsorption performance of Pb (lead ion), which is an evaluation item for tap water (tap water). It was investigated. A composite adsorbent was prepared by uniformly mixing 10 g of the metal ion adsorbent obtained by preparing each prototype and 90 g of the above-mentioned granular activated carbon (CN5100S). A stainless steel column having a diameter of 40 mm was filled with 54 cc of the composite adsorbent to prepare a filtration member.

[Evaluation of fine powder generation]
RO water was passed through each filtration member including each prototype at a flow rate of 2.0 L / min (SV: 2222 hr ^-1). 100 mL of water that passed through the filtration member at the initial stage of water flow (from the start of water flow) was collected, and the absorbance of the collected water was measured by a spectrophotometer (manufactured by Shimadzu Corporation: UVmini-1240, wavelength 660 nm, using a 100 mm cell). Asked. The lower the absorbance, the more transparent it is, and the higher the absorbance, the more turbid it becomes.

[Measurement of soluble lead removal performance]
Raw water containing 50 ppb of soluble lead was prepared for each filtration member including each prototype, and water was passed through at a flow rate of ^{2.0 L / min (SV: 2222 hr -1).} The removal rate of soluble lead (lead ions) by the filtration member is measured, and the value obtained by dividing the amount of water flow when the removal rate reaches 80% by the filling amount (54 cc) of the composite adsorbent is the performance value (L / cc). ).
Soluble lead removal performance (L / cc) = Water flow rate (L) when the removal rate reaches 80% / Filling amount of composite adsorbent (54 cc)

Tables 5 to 8 show the initial fine powder value (ABS) and the removal performance of soluble lead (L / cc) of each prototype and a filtration member made of a composite adsorbent using activated carbon.

Based on Tables 1 to 8 above, the evaluations and comprehensive evaluations of each test result are summarized in Tables 9 to 12.
When the intensity index (%) was 86.0 or more, it was set as "A", when it was 80.0 to 85.9, it was set as "B", and when it was 79.9 or less, it was set as "C".
Those having a metal ion adsorption rate (%) of 90% or more are all designated as "A", those of 1 to 3 types having a metal ion adsorption rate of less than 90% are designated as "B", and those of all 4 types having a metal ion adsorption rate of less than 90% are designated as "C". bottom.
Those having an initial fine powder value (ABS) of 0.230 or less were designated as "A", those having an initial fine powder value (ABS) of 0.231 to 0.300 were designated as "B", and those having an initial fine powder value (ABS) of 0.301 or more were designated as "C".
Those with a soluble lead removal performance (L / cc) of 34.0 or more are designated as "A", those with 22.0 to 33.9 are designated as "B", and those with a solubility of 21.9 or less are designated as "C". And said.
In the overall evaluation, those with all four items above "A" are rated as "◎", those other than "◎" without "C" are rated as "○", and "C" is If it is 1, it is regarded as "Δ", and if all four items are "C", it is regarded as "x".

[Results and discussion of strength index of metal ion adsorbent]
All of Prototype Examples 8 to 12 in which a polyethylene-based resin binder is not used as the binder have a strength index of "C" and have not reached a satisfactory level. From this, as disclosed in Prototype Examples 1 to 7, the member that binds to the sodium titanate salts to form a granulated product that is hard to break is a polyethylene-based resin binder.

Further, in the prototype examples 15 and 17 in which the amount of the binder is increased, the strength index is improved by improving the binding force. On the contrary, in the prototype examples 13 and 16 in which the amount of the binder was reduced, the strength index decreased. In particular, the results of Prototype Example 13 in which the blending amount of the ethylene-vinyl acetate polymer, which is a polyethylene-based resin binder, is 4.0% by weight with respect to 100 parts by weight of the sodium titanate salt, and fine powder polyethylene, which is a polyethylene-based resin binder. From the results of Prototype Example 16 in which the blending amount of the above was 5.0% by weight, it was clarified that the lower limit thereof is preferably 6.0% by weight or more.

[Adsorption results and discussion of metal ion adsorbent]
Although all of Prototype Examples 10 to 12 show the adsorption performance of metal ions, they do not reach a satisfactory level. Further, since the results of the prototype examples 15 and 17 in which the amount of the binder is increased are the same, the polyethylene-based resin binder is blended from the viewpoint of ensuring a certain adsorption performance in view of the adsorption performance of the prototype examples 3 to 5 and 14. The upper limit of the amount is considered to be 20.0% by weight.

[Results and consideration of the initial amount of fine powder in the filtration member]
In all of Prototype Examples 8 to 14 and 16, the initial amount of fine powder does not reach a satisfactory level. From the results of Prototype Examples 1 to 7, 15 and 17, it was shown that the polyethylene-based resin binder was good in suppressing the generation of fine powder. It was confirmed that the type of binder used for the metal ion adsorbent constituting the filtration member (composite adsorbent) is preferably a polyethylene-based resin binder, and the lower limit of the blending amount is preferably 6.0% by weight or more. rice field. For this reason, activated carbon, which has been widely used in water purifiers, is adsorbed (filtered and collected) by combining a metal ion adsorbent (granular substance of alkali metal titanate) with metal ion adsorption performance. ) The target can be easily expanded.

[Results and discussion of soluble lead removal performance of filtration members]
Although all of Prototype Examples 10 to 12 and 15 to 17 show the adsorption (removal) performance of soluble lead (lead ion), they do not reach a satisfactory level. In addition, since all of Prototype Examples 1 to 4 showed good results, among the polyethylene-based resin binders used for the metal ion adsorbent constituting the filtering member (composite adsorbent), polyethylene and ethylene- It was clarified that good results were obtained when an α-olefin copolymer or an ethylene-vinyl acetate copolymer was used. In Prototype Examples 15 and 17 in which the amount of the binder is increased, the generation of fine powder is suppressed by improving the binding force. However, the adsorption performance is lowered by that amount. On the contrary, in the prototype examples 13 and 14 in which the amount of the binder was reduced, the generation of fine powder increased.

[Results and consideration of comprehensive evaluation]
From the comparison of each prototype, the effectiveness of the polyethylene-based resin binder was shown in the type of binder used for the metal ion adsorbent, and in particular, polyethylene, ethylene-α-olefin copolymer, or ethylene-vinyl acetate copolymer. Better results are obtained when coalescence is used. Further, comparing Prototype Examples 1 to 5 with Prototype Examples 6 and 7, when the binder is in the form of an emulsion, the strength index, the adsorption performance of metal ions, the amount of fine powder and the removal performance of soluble lead are all good. The result was shown. It is considered that this is because the binder is in the form of an emulsion, so that the crystalline fine particles of the metal ion adsorbent and the binder are easily blended and mixed evenly.

Since the present invention is granulated by mixing a titanoic acid alkali metal salt crystal-grown by the flux method with a polyethylene-based resin binder, the metal ion adsorbent is easy to handle and is good. Then, by combining the metal ion adsorbent with activated carbon, a composite adsorbent that makes the best use of the adsorption abilities of both can be obtained. Further, an efficient filtration member can be obtained by using the composite adsorbent.

C Activated carbon Am Metal ion adsorbent M Composite adsorbent 10 Filtration member 11 Container body 12 Lid 14 Water guide 16 Permeation hole 20 Water purifier 21 Switching part 23 Filtration chamber 25 Faucet

Claims (8)

Crystalline fine particles of an alkali metal titanate crystal grown using the flux method,
It is characterized in that it is a crystalline fine particle mixture obtained by binding and granulating the crystalline fine particles by mixing and heating with a polyethylene resin binder having a weight corresponding to 6 to 20% by weight of the crystalline fine particles. Metal ion adsorbent. The metal ion adsorbent according to claim 1, wherein the alkali metal titanate is a sodium titanate salt. The metal ion adsorbent according to claim 2, wherein the flux agent is sodium nitrate in growing crystals of the sodium titanate. The metal ion adsorbent according to any one of claims 1 to 3, wherein the crystalline fine particles have an average particle size of 1 to 100 μm. The metal ion adsorbent according to any one of claims 1 to 4, wherein the polyethylene-based resin binder is in the form of an emulsion. The metal ion adsorbent according to any one of claims 1 to 5, wherein the polyethylene-based resin binder is a polyethylene, an ethylene-α-olefin copolymer, or an ethylene-vinyl acetate copolymer. A composite adsorbent containing the crystalline fine particle mixture according to any one of claims 1 to 6 and activated carbon. A filtration member comprising the composite adsorbent according to claim 7.

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