JP2015229122A - Metal ion adsorbent material, and combined adsorbent material obtained by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new metal ion adsorbent material in which alkali metal titanate salt is used as an adsorbent material different from an existing ion exchange resin or zeolite and deterioration of whose adsorption capacity is suppressed though a binder is used, to provide a combined adsorbent material obtained by using the metal ion adsorbent material, and to provide a filtration member.SOLUTION: The metal ion adsorbent material is obtained by mixing a crystalline fine particle of sodium salt of titanic acid, a crystal of which particle is grown by a flux method using sodium nitrate as a flux agent, with a silica-based binder which is derived from colloidal silica or water glass and the weight of which is equivalent to 20-40 wt.% of the crystalline fine particle. The combined adsorbent material is obtained by mixing the metal ion adsorbent material with activated carbon. The filtration member includes the combined adsorbent material.

Description

  The present invention relates to a metal ion adsorbent and a composite adsorbent using the metal ion adsorbent, and in particular, is a metal ion adsorbent having enhanced metal ion adsorption performance using an alkali metal titanate, and a composite adsorbent using the same. About.

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

  However, since activated carbon is generally not suitable for adsorption of metal ions, it is common to use activated carbon in combination with other adsorbents. Specifically, a combination of activated carbon and an organic adsorbent such as an ion exchange resin, 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 an increase in water demand accompanying a population increase and environmental deterioration.

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

  For example, a heavy metal ion adsorbent has been proposed in which a zeolite in which 60 mol% or more of the total exchangeable cation amount is substituted with calcium ions and / or magnesium ions is attached to the surface of activated carbon using a binder (patent) Reference 1). Also, a composite powder obtained by adhering a plastic powder to a fine particle compound comprising an amorphous titanosilicate compound or an A-type or X-type zeolite in an amount of 3 to 20% by weight, and powder, granular and fibrous materials There has been proposed a composite adsorbent comprising at least one selected plastic powder and an adsorbent that has not been adhered (see Patent Document 2).

  The adsorbent using the above zeolite has good metal ion adsorption performance. However, it has been pointed out that aluminum may be eluted from zeolite contained in the adsorbent. Therefore, another adsorbent is required. Moreover, since adsorption materials, such as a zeolite, are aggregated using a resin binder, adsorption | suction performance is not fully exhibited.

  From a series of circumstances, it is difficult to achieve downsizing of the adsorption apparatus according to the adsorbents of ion exchange resin, hydroxyapatite, and zeolite described above. For example, further improvement in performance is required in consideration of efficiently adsorbing various objects in a small number of installation places, such as household water purifiers. Therefore, an adsorbent that is effective for adsorbing new metal ions, particularly heavy metal ions, different from any of existing ion exchange resins, hydroxyapatite, and zeolite has been demanded.

International Publication WO2005 / 009610 Japanese Patent No. 4361489

  Based on such circumstances, the inventors sought a new adsorbent and found that the alkali metal titanate is good for adsorption of metal ions. Furthermore, earnest research was repeated and it came to complete the new adsorbent material which can be aggregated with a binder, without reducing the metal ion adsorption capability of alkali metal titanate.

  The present invention has been proposed in view of the above situation, and uses an alkali metal titanate as an adsorbent different from existing ion exchange resins, hydroxyapatite, and zeolite, and further adsorbs while using a binder. Provided are a new metal ion adsorbent that suppresses a decrease, and a composite adsorbent and a filtration member using the same.

  That is, the invention of claim 1 is a mixture of an alkali metal titanate crystalline fine crystal grown by a flux method and a silica-based binder having a weight corresponding to 20 to 40% by weight of the crystalline fine particle. The present invention relates to a metal ion adsorbent characterized by comprising:

  The invention of claim 2 relates to the metal ion adsorbent according to claim 1, wherein the alkali metal titanate is sodium titanate.

  The invention of claim 3 relates to the metal ion adsorbent according to claim 2, wherein the fluxing agent is sodium nitrate when the sodium titanate salt is grown.

  The invention according to claim 4 relates to the metal ion adsorbent according to any one of claims 1 to 3, wherein the crystalline fine particles have an average particle diameter of 1 to 100 μm.

  The invention according to claim 5 relates to the metal ion adsorbent according to any one of claims 1 to 4, wherein the silica-based binder is colloidal silica.

  The invention according to claim 6 relates to the metal ion adsorbent according to claim 5, wherein the colloidal silica is colloidal silica particles having a particle diameter of 4 to 20 nm present in an aqueous dispersion having a pH of 2 to 4.

  The invention according to claim 7 relates to the metal ion adsorbent according to any one of claims 1 to 4, wherein the silica-based binder is water glass.

  The invention of claim 8 relates to a composite adsorbent characterized by mixing the metal ion adsorbent according to any one of claims 1 to 7 and activated carbon.

  A ninth aspect of the present invention relates to a filtration member comprising the composite adsorbent according to the eighth aspect.

  According to the metal ion adsorbing material of the first aspect of the invention, the crystalline fine particles of alkali metal titanate salt grown using the flux method and the silica-based weight corresponding to 20 to 40% by weight of the crystalline fine particles Because it is mixed with a binder, alkali metal titanate is used as an adsorbent different from existing ion exchange resins, hydroxyapatite, and zeolite, and it is possible to suppress a decrease in adsorption capacity while using a binder. it can.

  According to the metal ion adsorbent according to the invention of claim 2, since the alkali metal titanate is sodium titanate in the invention of claim 1, it can be manufactured at low cost.

  According to the metal ion adsorbent according to the invention of claim 3, in the invention of claim 2, since the fluxing agent is sodium nitrate during the crystal growth of the sodium titanate salt, the metal component does not become an impurity and is washed with water. Cleaning and removal are possible. Also, the nitric acid content can be volatilized by heating and is not easily an impurity.

  According to the metal ion adsorbent according to the invention of claim 4, in the invention of any one of claims 1 to 3, since the average particle diameter 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 invention of claim 5, in the invention of any one of claims 1 to 4, since the silica-based binder is colloidal silica, it is not hydrophobic (water repellent) like a resin binder. It is hydrophilic and has high affinity with the metal ions to be adsorbed.

  According to the metal ion adsorbent according to the invention of claim 6, in the invention of claim 5, the colloidal silica is colloidal silica particles having a particle diameter of 4 to 20 nm present in an aqueous dispersion having a pH of 2 to 4. Thus, it is possible to perform good granulation of the crystalline fine particles and good metal ion adsorption.

  According to the metal ion adsorbent according to the invention of claim 7, in the invention of any one of claims 1 to 4, since the silica-based binder is water glass, it is not hydrophobic (water repellent) like a resin binder. It is hydrophilic and has high affinity with the metal ions to be adsorbed.

  Since the composite adsorbent according to the invention of claim 8 is formed by mixing the metal ion adsorbent according to any one of claims 1 to 7 and activated carbon, the composite adsorbent can cope with a wider variety of adsorption objects. it can.

  Since the filter member according to the invention of claim 9 has the composite adsorbent according to claim 8, application to a water purifier becomes simple.

It is a schematic process drawing explaining manufacture of the metal ion adsorption material of this invention. It is the schematic which shows the usage example of the composite adsorption material of this invention. It is the schematic which shows the usage example of the filtration member of this invention.

  As defined in the invention of claim 1, the metal ion adsorbent of the present invention is formed by mixing the crystalline fine particles of alkali metal titanate and the silica-based binder and agglomerating, and forming as an appropriate granular material by granulation. The Metal ions are trapped in the crystal lattice of the alkali metal titanate. These metal ions are mainly heavy metal ions such as lead, iron, manganese, zinc, copper, and cadmium. Then, by combining a granulated product of crystalline fine particles of the alkali metal titanate with a different kind of adsorbent, a composite adsorbent with a wider range of adsorption objects is finished.

  An alkali metal titanate 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 a flux method. The advantage of the flux method is that the melting point when the raw material compound is melted can be lowered by adding a flux agent described later together. For this reason, the energy efficiency required for production is improved. Moreover, the process and time from a raw material compound to a final product can be shortened. The metal ion adsorbent is a filter medium, so it is required in large quantities. Also from this fact, the flux method capable of mass production with high production efficiency is extremely effective.

  The alkali metal titanate can be any of sodium salt, potassium salt, lithium salt and the like. In this case, as defined in the invention of claim 2, sodium titanate that can be manufactured at low cost in consideration of the results of the examples of metal ion adsorption described later and raw material costs is preferable. The alkali metal titanate is trititanate, mainly sodium trititanate. In addition, crystal forms such as dititanate and tetratitanate are also included. In the case of the flux method, since it is a short-time reaction at a low melting point, it is considered that a plurality of crystal types are likely to be generated.

  In the crystal growth of alkali metal titanate, sodium carbonate, sodium chloride, potassium carbonate, potassium chloride or the like is used as the alkali metal salt as a raw material. And titanium oxide is added. Titanium oxide is preferably anatase type. Titanium oxide is preferably used in the form of powder from the viewpoint of workability.

  Then, sodium nitrate is used as a fluxing agent for the alkali metal salt and titanium oxide as defined in the invention of claim 3. Sodium nitrate is the same metal component as the above-mentioned alkali metal salt sodium carbonate and does not become an impurity, and can be washed away with water. In addition, the nitric acid content of sodium nitrate can be volatilized by heating and is hardly an impurity. Which compound is used for the fluxing agent is selected in consideration of conditions such as the type of the raw material compound and the control of the melting temperature.

  Crystalline fine particles of alkali metal titanate that have been crystal-grown using the flux method are finer than particles produced by normal crystal growth. In this case, as defined in the invention of claim 4, the average particle diameter 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 advantages of a low melting point and a short time, the time required for crystal growth is shortened accordingly, and it is not easy to grow large crystals.

  As described above, if the crystalline fine particles are left as they are, there is a possibility that it takes time for the precipitation or they flow out into the running water when they are incorporated in the filtration member. Therefore, it can be said that it is advantageous if the crystalline fine particles can be aggregated and processed into a larger granular material while suppressing a decrease in the ability to adsorb the metal ions of the alkali metal titanate. Therefore, as defined in the first aspect of the invention, in order to granulate by bonding the crystalline fine particles, a silica-based material having a weight corresponding to 20 to 40% by weight of the crystalline fine particles of the alkali metal titanate. A binder is blended.

  The silica-based binder is not hydrophobic (water repellent) like existing resin binders but hydrophilic. For this reason, the affinity between the silica-based binder and the metal ions to be adsorbed dissolved in water is high. Further, the adsorption of metal ions is reduced at the portion covered with the resin binder. However, in the case of a silica-based binder, the silicon oxide lattice does not extremely suppress the transmission of metal ions to be adsorbed. Therefore, silica-based binders are extremely advantageous. Such a silica-based binder is colloidal silica or water glass as defined in the invention of claim 5 or 7.

  Colloidal silica is a sol in which silicon oxide and its hydrate are dispersed in water. The size, pH, and the like of particles generated by aggregation of silicon oxide and hydrate vary depending on the application. If the amount of colloidal silica is less than 20% by weight of the crystalline fine particle weight of the alkali metal titanate, the amount is too small and the granulation of the crystalline fine particles (microcrystals) is incomplete and the outflow increases. On the other hand, if it exceeds 40% by weight, the amount becomes too large, which hinders metal ion adsorption.

  In particular, when the purpose is to bind and adsorb the crystalline fine particles of alkali metal titanate, colloidal silica has a pH of 2 to 4 as defined in the invention of claim 6 and as described in detail in the examples. The colloidal silica particles present in the acidic region and present in the aqueous dispersion have a size of 4 to 20 nm.

  In the case where the colloidal silica is alkaline, it is generally considered that precipitation is likely to occur due to the reaction between the metal ions and the alkali, and the metal ions are easily insolubilized. Therefore, the adsorption performance of metal ions is deteriorated under the influence of the colloidal silica solution. From this, the colloidal silica which can be obtained will be examined, and the above pH will be in a suitable range.

  Next, in the case of colloidal silica particles having a particle diameter exceeding 20 nm, the colloidal silica particles are too large. For this reason, it is difficult to enter the gaps between the crystalline fine particles of the alkali metal titanate and it is difficult to obtain a strong binding. Therefore, considering the available colloidal silica, the particle diameter is in a suitable range.

  Water glass used as a silica-based binder is a viscous liquid of sodium silicate (in a state where anhydrous silicic acid and sodium oxide are mixed). Water glass has been used extensively, for example, to harden sand and cement for castings. In particular, it is effective in binding applications of inorganic materials. Therefore, it was used because it was also effective for binding of crystalline fine particles of alkali metal titanate. Also in the use of water glass, water glass having a weight corresponding to 20 to 40% by weight of the crystalline fine particles of alkali metal titanate is blended in the same manner as the colloidal silica described above.

  Similarly to the above-mentioned colloidal silica, the amount of water glass is too small and the outflow of microcrystals increases when the amount of water glass is less than 20% by weight of the crystalline fine particles of alkali metal titanate. On the other hand, if it exceeds 40% by weight, the amount becomes too large, which hinders metal ion adsorption. As long as the colloidal silica and the water glass satisfy the above-mentioned regulations, they exhibit the same performance.

Then, the manufacturing process of a metal ion adsorbent is demonstrated, using the schematic process drawing of FIG. First, alkali metal salts (Na ₂ CO _{3 and the} like) and titanium oxide (TiO _{2 and the} like) as raw materials are weighed and prepared in predetermined amounts. A fluxing agent (NaNO ₃ or the like) is also added here after a predetermined measurement. These three types of compounds are heated to about 500 ° C. to 600 ° C., and crystal growth proceeds. Thus, first, crystalline fine particles of alkali metal titanate can be obtained. When growing a crystal of an alkali metal titanate without adding a fluxing agent, heating at 1000 ° C. or higher is usually required.

  Crystalline fine particles of alkali metal titanate are appropriately washed with water, and a silica-based binder (colloidal silica or water glass) is added. Spraying or the like is preferred because it becomes difficult to dry if there is too much moisture throughout. Here, the crystalline fine particles aggregate through kneading to form a granulated product. Thereafter, the granulated product is dried and sufficiently solidified. Thereafter, the particles are classified by particle size through sieving with a cyclone or a sieve having a desired opening. In this way, a metal ion adsorbent that is a granulated product of crystalline fine particles of alkali metal titanate is completed.

  The metal ion adsorbent described in detail so far exhibits an effect on adsorption of heavy metal ions such as lead, iron, manganese, zinc, copper, cadmium and the like, as disclosed in the examples described later. Therefore, as defined in the invention of claim 8, a composite adsorbent is formed by mixing a metal ion adsorbent and activated carbon effective for adsorbing various organic compounds. Activated carbon can cope with various adsorption targets by controlling its pores. For example, activated carbon disclosed in Japanese Patent Application Laid-Open No. 2013-220413 or the like is suitable for use for adsorbing trihalomethanes.

  As can be understood from the schematic diagram of FIG. 2, the composite adsorbent M can be obtained by mixing the metal ion adsorbent Am and the activated carbon C in appropriate amounts. For example, the composite adsorbent M is accommodated in the filtering member 10 in FIG. A fine permeation hole 16 is formed in the surface portion 15 of the container body 11 of the filtration member 10. A water guide 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 accommodated.

  Thus, as defined in the ninth aspect of the invention, the filter member 10 having the composite adsorbent M is completed. The water to be treated (water before treatment) enters the inside through the permeation holes 16 in the surface portion 15 of the filter member 10. Then, when the water to be treated comes into contact with the composite adsorbent M, adsorption and filtration proceed. And the to-be-processed water after filtration (water after a process) flows out of the filtration member 10 from the water guide part 14. FIG.

  A water purifier is mentioned as the main use of the said filtration member. As shown in the schematic diagram of FIG. 3, the water purifier 20 is attached to the tip of the tap 25 of the water supply. A filtration chamber 23 is provided on the side of the water switching unit 21. The filtration member 10 is accommodated 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 attached to the water purifier 20 as necessary. Of course, the illustration is an example of a filtering member, and therefore other forms are also possible. Furthermore, it is possible to make a large-scale processing apparatus assuming use in a stationary type or a factory. In particular, it is effective for water treatment of drinking water such as tap water (tap water).

[Raw materials]
Sodium titanate was used as the alkali metal titanate. Sodium titanate is mixed with sodium carbonate (manufactured by Daito Chemical Co., Ltd.), titanium oxide (manufactured by Teika Co., Ltd.), and sodium nitrate as a flux agent (manufactured by Ube Industries, Ltd.). Then, it was sealed and heated at 600 ° C. for 10 hours to grow crystals. Thereafter, crystalline fine particles of sodium titanate were prepared through appropriate water washing (the preparation is a sodium titanate salt grown by a flux method). The crystalline fine particles were measured with a laser diffraction / scattering particle size / particle size distribution measuring device (manufactured by Shimadzu Corporation: SALD-3000S). The average particle diameter was the particle diameter at an integrated value of 50% in the particle size distribution obtained by the laser diffraction / scattering method using the same measuring apparatus.

Furthermore, as a sodium titanate salt grown without using the flux method, sodium trititanate (Na ₂ O ₇ Ti ₃ , No. 93-1197) manufactured by Stream Chemicals was used.

The following types of colloidal silica (silica-based binder) were used.
NISSAN CHEMICAL INDUSTRIES, INC .: Snowtech O (particle size 10-20 nm, pH 2-4)
{Hereafter referred to as C1. }
Company-made: Snowtech OS (particle size 4-6nm, pH 2-4)
{Hereafter referred to as C2. }
Company-made: Snowtech N (particle size 10-20 nm, pH 9-10)
{Hereafter referred to as C3. }
Company-made: Snowtech OL (particle size 40-50 nm, pH 2-4)
{Hereafter referred to as C4. }
Made by ADEKA Corporation: AT-20Q (particle size 10-20 nm, pH 2-4)
{Hereafter referred to as C5. }
Aichi Silicon Industrial Co., Ltd .: Surfroid 20 (particle size 10-20 nm, pH 9-10)
{Hereafter referred to as C6. }
As water glass (silica-based binder), water glass (solute concentration 52%) manufactured by Wako Pure Chemical Industries, Ltd. was used. {Hereafter referred to as S1. }

The following were used as other binders (binders).
Manufactured by Taki Chemical Co., Ltd .: primary aluminum phosphate, manufactured by Sumitomo Seika Co., Ltd .: polyethylene fine powder, Frocene UF-1.5
Mitsui Chemicals, Inc .: Polyethylene emulsion, Chemipearl M200
Asahi Glass Co., Ltd .: PTFE emulsion, FLUON (registered trademark)

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

[Preparation of metal ion adsorbent]
As in Examples 1 to 6 and Comparative Examples 1 to 8 disclosed in Tables 1 to 3, metal ion adsorbents were prepared by mixing sodium titanate crystal and various silica binders. And it used for adsorption | suction of various metal ions in a table | surface, and measured the adsorption rate for every metal ion.

[Example 1]
100 mL of colloidal silica (C1) (diluted to 20% solute) was sprayed and uniformly mixed with 60 g of sodium titanate salt grown by the flux method crystal. The mixture was heat-dried at 150 ° C. for 2 hours. Thereafter, the mixture was passed through a 50/100 mesh (upper mesh opening 0.30 mm, lower mesh opening 0.15 mm) sieve, and the mixture remaining on the sieve was used as a metal ion adsorbent (Example 1). In Example 1, 33% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Example 2]
100 mL of colloidal silica (C2) (diluted to 20% solute) was sprayed and uniformly mixed with 60 g of sodium titanate salt grown by the flux method crystal. The mixture was heat-dried at 150 ° C. for 2 hours. Thereafter, the mixture was passed through a 50/100 mesh sieve as described above, and the mixture remaining on the sieve was used as a metal ion adsorbent (Example 2). In Example 2, 33% by weight of sodium titanate salt weight corresponds to the binder weight.

Example 3
100 mL of colloidal silica (C5) (diluted to 20% solute) was sprayed and uniformly mixed with 60 g of sodium titanate salt grown by the flux method crystal. The mixture was heat-dried at 150 ° C. for 2 hours. Thereafter, the mixture was passed through a 50/100 mesh sieve as described above, and the mixture remaining on the sieve was used as a metal ion adsorbent (Example 3). In Example 3, 33% by weight of the sodium titanate salt weight corresponds to the binder weight.

Example 4
100 mL of colloidal silica (C2) (diluted to 13% solute) was sprayed and uniformly mixed with 60 g of sodium titanate salt grown by the flux method crystal. The mixture was heat-dried at 150 ° C. for 2 hours. Thereafter, the mixture was passed through a 50/100 mesh sieve as described above, and the mixture remaining on the sieve was used as a metal ion adsorbent (Example 4). In Example 4, 22 wt% of the sodium titanate salt weight corresponds to the binder weight.

Example 5
20 g of water glass (S1) was dissolved in 100 mL of ion exchange water to obtain a water glass solution. 100 mL of this water glass solution was sprayed and uniformly mixed with 60 g of sodium titanate salt grown by the flux method crystal. The mixture was heat-dried at 150 ° C. for 2 hours. Thereafter, the mixture was passed through a 50/100 mesh sieve as described above, and the mixture remaining on the sieve was used as a metal ion adsorbent (Example 5). In Example 5, 33% by weight of the sodium titanate salt weight corresponds to the binder weight.

Example 6
16 g of water glass (S1) was dissolved in 100 mL of ion exchange water to obtain a water glass solution. 100 mL of this water glass solution was sprayed and uniformly mixed with 60 g of sodium titanate salt grown by the flux method crystal. The mixture was heat-dried at 150 ° C. for 2 hours. Thereafter, the mixture was passed through a 50/100 mesh sieve as described above, and the mixture remaining on the sieve was used as a metal ion adsorbent (Example 6). In Example 6, 22% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Comparative Examples 1, 2, 3]
In Comparative Example 1, colloidal silica (C3) (diluted to 20% solute) was used, and a metal ion adsorbent was prepared in the same manner as in Example 1 except for other conditions.
In Comparative Example 2, colloidal silica (C4) (diluted to a solute of 20%) was used, and a metal ion adsorbent was prepared in the same manner as in Example 1 except for other conditions.
In Comparative Example 3, colloidal silica (C6) (diluted to 20% solute) was used, and a metal ion adsorbent was prepared in the same manner as in Example 1 except for other conditions.
In Comparative Examples 1, 2 and 3, 33% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Comparative Example 4]
50 mL of the above-mentioned primary aluminum phosphate (solute concentration 41.5%) was sprayed and uniformly mixed with 60 g of sodium titanate salt grown by the flux method crystal. The mixture was heat-dried at 150 ° C. for 2 hours. Thereafter, the mixture was passed through a 50/100 mesh sieve as described above, and the mixture remaining on the sieve was used as a metal ion adsorbent (Comparative Example 4). In Comparative Example 4, 34.6% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Comparative Example 5]
The above polyethylene fine powder 3.2 g was added to 60 g of sodium titanate salt grown by the flux method crystal and mixed uniformly. The mixture was heat-dried at 150 ° C. for 2 hours. Thereafter, the mixture was passed through a 50/100 mesh sieve as described above, and the mixture remaining on the sieve was used as a metal ion adsorbent (Comparative Example 5). In Comparative Example 5, 5.3 wt% of the sodium titanate salt weight corresponds to the binder weight.

[Comparative Example 6]
The above polyethylene emulsion (solute concentration 40%) 8 mL was sprayed and uniformly mixed with 60 g of sodium titanate salt grown by the flux method crystal. The mixture was heat-dried at 150 ° C. for 2 hours. Thereafter, the mixture was passed through a 50/100 mesh sieve as described above, and the mixture remaining on the sieve was used as a metal ion adsorbent (Comparative Example 6). In Comparative Example 6, 5.3 wt% of the sodium titanate salt weight corresponds to the binder weight.

[Comparative Example 7]
The above-mentioned PTFE emulsion (solute concentration 60%) 15 mL was sprayed and uniformly mixed with 60 g of sodium titanate salt grown by the flux method crystal. The mixture was heat-dried at 150 ° C. for 2 hours. Thereafter, the mixture was passed through a 50/100 mesh sieve as described above, and the mixture remaining on the sieve was used as a metal ion adsorbent (Comparative Example 7). In Comparative Example 7, 15 wt% of the sodium titanate salt weight corresponds to the binder weight.

[Comparative Example 8]
100 mL of colloidal silica (C1) (diluted to a solute of 20%) was sprayed and uniformly mixed with 60 g of sodium titanate salt (made by the above-mentioned Stream Chemicals) not based on the flux method. The mixture was heat-dried at 150 ° C. for 2 hours. Thereafter, the mixture was passed through a 50/100 mesh sieve as described above, and the mixture remaining on the sieve was used as a metal ion adsorbent (Comparative Example 8). In Comparative Example 8, 33% by weight of the sodium titanate salt weight corresponds to the binder weight.

[Metal ion adsorption test]
As measurement objects, six kinds of metal salts of Pb, Fe, Mn, Zn, Cu, and Cd were prepared. A test stock solution containing 6 kinds of metal ions was prepared by dissolving each metal ion concentration in ion exchange water at 100 μg / L. When measuring the amount of metal ions in water, Thermo Fisher Scientific Co., Ltd., atomic absorption photometer (iCE3000 series) was used.

  100 mL of the test stock solution was dispensed into a 300 mL Erlenmeyer flask, and 0.1 g each of the metal ion adsorbents of Examples and Comparative Examples was added. The Erlenmeyer flask was adsorbed by shaking for 24 hours. After stopping shaking, the mixture was allowed to stand for 1 hour, and the supernatant (supernatant) was collected and filtered through a disposable filter unit DISMIC (pore size 0.2 μm) manufactured by Toyo Roshi Kaisha, Ltd. The filtrate was measured with the atomic absorption photometer.

The adsorption rate (Ads) (%) of metal ions was calculated as follows and calculated for each of six types of metal ions for one example and comparative example.
Adsorption rate Ads (%) = [1-{(test stock solution concentration Ds−post-adsorption concentration Da) / test stock solution concentration Ds}] × 100

  For each example and comparative example, the type of sodium titanate, the type of binder, the particle size, the pH, the ratio of the binder weight to the sodium titanate salt weight (% by weight), and each metal ion of the metal ion adsorbent The adsorption rate (%) is shown, and a comprehensive evaluation (good / bad) is also given (see Tables 1 to 3). “Good” in the comprehensive evaluation is an example in which the adsorption rate of all six metal ions is 70% or more. The overall evaluation “No” is an example in which there is less than 70% even for one type.

[Adsorption results and discussion of metal ion adsorbents]
Comparative Example 4 is an example using a binder such as sand for casting, and Comparative Examples 5 to 7 are examples of known resin binders. None of them reach a satisfactory level while exhibiting metal ion adsorption performance. From this, the member that shows good metal ion adsorption performance and binds sodium titanate salts is a silica-based binder of both colloidal silica and water glass as disclosed in Examples 1 to 6.

  When sodium titanate constituting the metal ion adsorbent was compared with respect to crystal growth by the flux method, from Comparative Example 8, the sodium titanate produced by a method not using the flux method has limited metal species that can be adsorbed. It has been found. In particular, the metal ion adsorbent of Comparative Example 8 surprisingly does not adsorb Mn and Zn. Also, the adsorbed metal species is clearly inferior to the examples. Therefore, assuming efficient adsorption of various metal ions, it is desirable to select sodium titanate salt grown by the flux method.

  Comparative Examples 1 and 3 are examples in which colloidal silica is used as the silica-based binder and the colloidal silica solution is made alkaline. Compared with Examples 1 and 3 in which the particle diameter and the mixing ratio of colloidal silica are the same, the adsorption rate of various metal ions is lowered. Presumably, the adsorption may be inhibited by the alkali component remaining in the colloidal silica before the adsorption with the sodium titanate. Therefore, it is desirable to select a colloidal silica solution in the acidic range of pH 2 to 4 in consideration of availability as in the examples.

  From Examples 1 and 2, if the particle diameter of colloidal silica is around 20 nm, good metal ion adsorption performance is exhibited. However, as in Comparative Example 2, when the particle size was increased by aligning the pH and the blending ratio, some metal ion adsorption performance decreased. Therefore, it is desirable that the particle diameter of colloidal silica be 4 to 20 nm in consideration of availability.

[Create composite adsorbent]
As described above, the inventor has clarified that the metal ion adsorbent disclosed in the examples exhibits a good adsorption ability for various metal ions. Based on this result, composite adsorbents were prepared by combining sodium titanate effective for metal ion adsorption and activated carbon which is widely used as existing adsorbents (Examples 7 to 13 and Comparative Examples 9 to 19). . Assuming that the composite adsorbent is used in actual water purifiers, the adsorbability of Pb (lead ion), which is an evaluation item for tap water (water supply), and the generation of fine powder due to water flow, the quality of the composite adsorbent It was investigated.

Example 7
A composite adsorbent (Example 7) was prepared by uniformly mixing 10 g of the metal ion adsorbent obtained by the preparation of Example 1 and 90 g of the above granular activated carbon (CN5100S).

[Examples 8, 9, 10, 12, 13]
The composite adsorbent of Example 8 was prepared by using the metal ion adsorbent prepared in Example 2 and using the same activated carbon as in Example 7 and the same blending weight.
The composite adsorbent of Example 9 was prepared by using the metal ion adsorbent prepared in Example 3 and using the same activated carbon as in Example 7 and the same blending weight.
The composite adsorbent of Example 10 was prepared by using the metal ion adsorbent prepared in Example 4 and using the same activated carbon as in Example 7 and the same blending weight.
The composite adsorbent of Example 12 was prepared by using the metal ion adsorbent prepared in Example 5 and using the same activated carbon and the same blending weight as in Example 7.
The composite adsorbent of Example 13 was prepared by using the metal ion adsorbent prepared in Example 6 and using the same activated carbon as in Example 7 and the same blending weight.

Example 11
100 mL of colloidal silica (C1) (diluted to solute 22.4%) was sprayed and uniformly mixed with 60 g of sodium titanate salt grown by the flux method crystal. The mixture was heat-dried at 150 ° C. for 2 hours. Thereafter, the mixture was passed through a 50/100 mesh sieve as described above, and the mixture remaining on the sieve was used as a metal ion adsorbent. 37.3% by weight of the sodium titanate salt weight corresponds to the binder weight. A composite adsorbent (Example 11) was prepared by uniformly mixing 10 g of the metal ion adsorbent and 90 g of the granular activated carbon (CN5100S, hereinafter the same).

[Comparative Examples 9, 10, 11]
The composite adsorbent of Comparative Example 9 was prepared by using the metal ion adsorbent prepared in Comparative Example 1, using the same activated carbon as in Example 7 and the same blending weight.
The composite adsorbent of Comparative Example 10 was prepared by using the metal ion adsorbent prepared in Comparative Example 2, using the same activated carbon as in Example 7 and the same blending weight.
The composite adsorbent of Comparative Example 11 was prepared by using the metal ion adsorbent prepared in Comparative Example 3, using the same activated carbon as in Example 7 and the same blending weight.

[Comparative Example 12]
100 mL of colloidal silica (C1) (diluted to solute 26.4%) was sprayed and uniformly mixed with 60 g of sodium titanate salt grown by flux method crystal. The mixture was heat-dried at 150 ° C. for 2 hours. Thereafter, the mixture was passed through a 50/100 mesh sieve as described above, and the mixture remaining on the sieve was used as a metal ion adsorbent. 44% by weight of the sodium titanate salt weight corresponds to the binder weight. A composite adsorbent (Comparative Example 12) was prepared by uniformly mixing 10 g of the metal ion adsorbent and 90 g of the granular activated carbon described above.

[Comparative Example 13]
100 mL of colloidal silica (C1) (diluted to a solute of 11.2%) was sprayed and uniformly mixed with 60 g of sodium titanate salt grown by the flux method crystal. The mixture was heat-dried at 150 ° C. for 2 hours. Thereafter, the mixture was passed through a 50/100 mesh sieve as described above, and the mixture remaining on the sieve was used as a metal ion adsorbent. 18.7% by weight of the sodium titanate salt weight corresponds to the binder weight. A composite adsorbent (Comparative Example 13) was prepared by uniformly mixing 10 g of the metal ion adsorbent and 90 g of the granular activated carbon described above.

[Comparative Example 14]
25.0 g of water glass (S1) was dissolved in 100 mL of ion exchange water to obtain a water glass solution. 100 mL of this water glass solution was sprayed and uniformly mixed with 60 g of sodium titanate salt grown by the flux method crystal. The mixture was heat-dried at 150 ° C. for 2 hours. Thereafter, the mixture was passed through a 50/100 mesh sieve as described above, and the mixture remaining on the sieve was used as a metal ion adsorbent. 41.7% by weight of the sodium titanate salt weight corresponds to the binder weight. A composite adsorbent (Comparative Example 14) was prepared by uniformly mixing 10 g of the metal ion adsorbent and 90 g of the granular activated carbon described above.

[Comparative Example 15]
A water glass solution was prepared by dissolving 10.4 g of water glass (S1) in 100 mL of ion exchange water. 100 mL of this water glass solution was sprayed and uniformly mixed with 60 g of sodium titanate salt grown by the flux method crystal. The mixture was heat-dried at 150 ° C. for 2 hours. Thereafter, the mixture was passed through a 50/100 mesh sieve as described above, and the mixture remaining on the sieve was used as a metal ion adsorbent. 17.3% by weight of the sodium titanate salt weight corresponds to the binder weight. A composite adsorbent (Comparative Example 15) was prepared by uniformly mixing 10 g of the metal ion adsorbent and 90 g of the granular activated carbon described above.

[Comparative Examples 16, 17, 18, 19]
The composite adsorbent of Comparative Example 16 was prepared by using the metal ion adsorbent prepared in Comparative Example 4 and using the same activated carbon as in Example 7 and the same blending weight.
The composite adsorbent of Comparative Example 17 was prepared by using the metal ion adsorbent prepared in Comparative Example 5 and using the same activated carbon as in Example 7 and the same blending weight.
The composite adsorbent of Comparative Example 18 was prepared by using the metal ion adsorbent prepared in Comparative Example 6 and using the same activated carbon as in Example 7 and the same blending weight.
The composite adsorbent of Comparative Example 19 was prepared by using the metal ion adsorbent prepared in Comparative Example 7 and using the same activated carbon as in Example 7 and the same blending weight.

[Performance evaluation test]
[Evaluation of fine powder generation]
A water adsorption column (diameter 40 mm) made of stainless steel pipe was filled with 50 cc of the composite adsorbent of each of the examples and comparative examples. Tap water was passed through the packed water flow column at a flow rate of ¹ L / min (SV: 1200 hr ⁻¹ ). The water that passed through the water flow column at the initial stage of water flow (from the start of water flow) was collected. The absorbance of the collected water was determined using a spectrophotometer (UVmini-1240, wavelength 660 nm, using 100 mm cell) manufactured by Shimadzu Corporation. The lower the absorbance, the more transparent, and the higher the turbidity. In addition, the water flow column filled with the composite adsorbent corresponds to a filtration member.

[Evaluation of soluble lead filtration performance]
The above-mentioned water flow column was packed with 50 cc of the composite adsorbent of each example and comparative example. Raw water containing 50 ppb soluble lead was prepared and passed through a packed column at a flow rate of 1.0 L / min (SV: 1200 hr ⁻¹ ). Measure the removal rate of soluble lead (lead ions) by the activated carbon composite material in the column, and calculate the value obtained by dividing the total water flow rate when the removal rate reaches 80% by the composite adsorbent packing amount (cc) It was set as the performance value (L / cc) of the composite adsorbent.

  In the performance evaluation (comprehensive evaluation) of the composite adsorbent, an example in which both the absorbance was 0.280 or less and the soluble lead filtration performance was 16.5 L / cc or more was evaluated as “good”. In the above two evaluations, if either one was not satisfied, “No” was evaluated. The evaluation results are shown in Tables 4 to 7. For each Example and Comparative Example, binder type, binder weight ratio (relative%), Examples and Comparative Examples corresponding to Tables 1 to 3, initial fine powder amount (Abs), soluble lead filtration performance (L / cc) The overall evaluation is shown.

[Results and discussion of performance evaluation test]
From Tables 4 and 5, the composite adsorbents of Examples 7 to 13 exhibited good soluble lead filtration performance by suppressing the generation of fine powder as a silica-based binder of either colloidal silica or water glass. For this reason, adsorption (filtering and collection) is performed by combining activated carbon, which has been widely used in water purifiers, with a metal ion adsorbent (particulate matter of alkali metal titanate) with metal ion adsorption performance. ) Can broaden the target easily.

  If it sees in more detail, about the comparative examples 9 and 11, from the same tendency as the above-mentioned Table 2, soluble lead filtration performance is not expected. In Comparative Example 10, it is considered that the binding force is reduced due to the size of the colloidal silica particles of the binder. From the comparison with Examples 10 to 13, Comparative Examples 12 and 13 are examples in which the binder amount of colloidal silica was increased or decreased. In Comparative Examples 14 and 15, the amount of water glass binder was increased or decreased. In Comparative Examples 12 and 14 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 reduced accordingly. On the contrary, in Comparative Examples 13 and 15 in which the amount of the binder was reduced, the generation of fine powder increased. Moreover, the improvement of adsorption | suction performance is not seen. Therefore, the amount of the silica-based binder to be blended is preferably an amount corresponding to 20 to 40% by weight of the alkali metal titanate salt.

  About Comparative Examples 16-19, although generation | occurrence | production of a fine powder is suppressed from the influence of resin, similarly to Comparative Examples 4-7 mentioned above, soluble lead filtration performance is not considered. For this reason, as disclosed in the respective examples, it is optimal to use colloidal silica or water glass silica-based binders instead of existing resin binders when granulating the alkali metal titanate.

  In particular, it is difficult to obtain large crystals of alkali metal titanate (sodium titanate) grown using the flux method. Therefore, the suppression of pulverization could be conveniently overcome by granulation with a silica-based binder. Therefore, the composite adsorbent is a good example for treating tap water such as a water purifier. The composite adsorbent is an aggregate of granular materials and has a simple composition. Therefore, the application of the composite adsorbent is wide. Therefore, a filtration member incorporating a composite adsorbent can be easily created. At the same time, it contributes to reducing the volume of the filter member.

  Since the present invention granulates an alkali metal titanate salt grown using a flux method, it is a good metal ion adsorbent. A composite adsorbent utilizing both adsorption capacities can be obtained by combining activated carbon with a metal ion adsorbent. Furthermore, an efficient filter member can be obtained by using a composite adsorbent.

C activated carbon Am metal ion adsorbent M composite adsorbent 10 filtration member 11 container main body 12 lid part 14 water transfer part 16 permeation hole 20 water purifier 21 switching part 23 filtration chamber 25 faucet

Claims (9)

Crystalline fine particles of alkali metal titanate grown using the flux method,
A metal ion adsorbent comprising a silica-based binder having a weight corresponding to 20 to 40% by weight of the crystalline fine particles.   The metal ion adsorbent according to claim 1, wherein the alkali metal titanate is sodium titanate.   The metal ion adsorbent according to claim 2, wherein the fluxing agent is sodium nitrate for crystal growth of the sodium titanate salt.   The metal ion adsorbent according to any one of claims 1 to 3, wherein the crystalline fine particles have an average particle diameter of 1 to 100 µm.   The metal ion adsorbent according to any one of claims 1 to 4, wherein the silica-based binder is colloidal silica.   6. The metal ion adsorbent according to claim 5, wherein the colloidal silica is colloidal silica particles having a particle diameter of 4 to 20 nm present in an aqueous dispersion having a pH of 2 to 4.   The metal ion adsorbent according to any one of claims 1 to 4, wherein the silica-based binder is water glass.   A composite adsorbent obtained by mixing the metal ion adsorbent according to any one of claims 1 to 7 and activated carbon.   A filtration member comprising the composite adsorbent according to claim 8.

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