JP2020049402A - Purifying material for treating water, and method of producing the same - Google Patents

Abstract

To provide a purifying material for treating water, which is not easily swollen by water and hence can be made to have a large purifying capacity per unit volume, and can be produced by low temperature calcination and hence can control thermal degradation of its purifying component, can increase its purifying capacity per unit mass, and can increase an amount of water that can be treated.SOLUTION: A glass frit and a water soluble polymer are added to and mixed with a metal titanate or a metal manganate, and the mixture is pelletized and calcined. Clay mineral, conventionally used as a binder, is hygroscopic and therefore a purifying material employing the clay mineral is easily swollen by water. A glass frit is not hygroscopic and therefore is not swollen by water. Hence, a purifying material for a water treatment employing a glass frit according to the present invention is not easily swollen by water and can be made to have a higher bulk density at a time of packing.SELECTED DRAWING: None

Description

  The present invention relates to a purification material for water treatment and a method for producing the same, and more particularly to a purification material for water treatment obtained by granulating and baking a metal titanate or a metal manganate which is a component for purifying contaminants in water with a binder. The present invention relates to a material and a method for manufacturing the same.

  As a purification material for water treatment for adsorbing and removing radioactive substances in water, Patent Document 1 discloses an adsorbent obtained by granulating a titanate such as potassium dititanate with a binder and firing the granulated material. Proposed. Patent Document 1 describes that a clay mineral such as attapulgite is used as a binder, and a water-soluble polymer such as polyvinyl alcohol (PVA) is further mixed as a plasticizer. Thus, by performing granulation and baking using a binder and a plasticizer, a spherical purifying material having sufficient handling durability can be manufactured without significantly impairing the purifying performance.

JP 2013-246145 A

A conventional purifying material using a clay mineral as a binder as in Patent Document 1 has the following problems.
(1) Since the volume swells when immersed in water, it is swollen with water before filling so that the adsorption tower is not blocked by the swelling of the purification material when used in the adsorption tower.
(2) Due to the swelling of the purification material, the bulk density at the time of filling the adsorption tower is reduced, and as a result, the adsorption capacity per unit volume of the purification material is reduced, and the amount of water that can be treated is reduced.
(3) Since the calcination is performed at a high temperature of 500 to 900 ° C., the original adsorption performance may be impaired due to thermal degradation (change in crystal structure) of potassium dititanate during calcination, and the adsorption capacity may be reduced.

  The present invention solves the above-mentioned conventional problems, hardly swells in water, and therefore has a large purification capacity per unit volume. An object of the present invention is to provide a purification material for water treatment, which has a large purification capacity per mass and can increase the amount of water that can be treated, and a method for producing the same.

  The present inventor has conducted intensive studies to solve the above problems, and as a result, by using glass frit as a binder, it can be manufactured by firing at a lower temperature than when using a clay mineral, and the amount of swelling due to water It has been found that a purification material for water treatment having a small water content can be obtained.

  The present invention has been achieved based on such knowledge, and has the following gist.

[1] A method for producing a purification material for water treatment, comprising mixing a metal titanate or a metal manganate, a glass frit and a water-soluble polymer, granulating the mixture, and firing the granulated material.

[2] The method for producing a purification material for water treatment according to [1], wherein the water-soluble polymer is carboxymethyl cellulose.

[3] The mixing amount of the glass frit to the metal titanate or the metal manganate is 5 to 40% by mass, and the mixing amount of the water-soluble polymer is 0.5 to 5% by mass. ] Or [2], the method for producing a purification material for water treatment according to [2].

[4] The method for producing a purifying material for water treatment according to any one of [1] to [3], wherein the granulated material has an average particle diameter of 150 to 3000 µm.

[5] The method for producing a purification material for water treatment according to any one of [1] to [4], wherein the granulated material is fired at a temperature equal to or higher than the softening point of the glass frit.

[6] A purification material for water treatment, comprising a mixture of a metal titanate or a metal manganate, a glass frit and a water-soluble polymer, and a calcined product of a granulated product.

[7] The purification material for water treatment according to [6], wherein the water-soluble polymer is carboxymethyl cellulose.

[8] The ratio of the glass frit to the metal titanate or the metal manganate is 5 to 40% by mass, and the ratio of the water-soluble polymer is 0.5 to 5% by mass [6] or The purification material for water treatment according to [7].

[9] The purification material for water treatment according to any one of [6] to [8], wherein the average particle diameter of the granulated product is 150 to 3000 µm.

[10] The purification material for water treatment according to any one of [6] to [9], wherein the softening point of the glass frit is 300 to 800 ° C.

According to the present invention, by using glass frit as a binder, firing at a lower temperature becomes possible as compared with the case of using a clay mineral, and thermal degradation of a purification component during firing can be suppressed. In addition, clay minerals conventionally used as binders have hygroscopicity, and therefore, a purifying material using clay minerals easily swells in water, but glass frit does not swell in water because it has no hygroscopicity. For this reason, the purification material for water treatment of the present invention using a glass frit is unlikely to swell with water, and can increase the bulk density at the time of filling.
From the above, according to the purification material for water treatment of the present invention, the purification performance per unit volume and per unit mass can be improved, and the amount of water that can be treated can be increased.

  Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments described below are intended to facilitate understanding of the present invention, and do not limit the present invention in any way. Can be implemented by variously changing each element disclosed in the following embodiments without departing from the scope of the invention.

<Purifying component>
The purifying component used in the present invention is a metal titanate or a metal manganate.

  The metal titanate has an ability to adsorb radioactive substances such as radioactive strontium, and is useful for purifying water containing radioactive substances.

The metal titanate is preferably an alkali metal titanate, particularly preferably an alkali metal titanate having a layered crystal structure. For example, potassium dititanate (K ₂ Ti ₂ O ₅ ), sodium trititanate (Na ₂ Ti ₃ O ₇ ) and potassium tetratitanate (K ₂ Ti ₄ O ₉ ).

The metal manganate preferably has a layered crystal structure or a tunnel-shaped crystal structure. Examples include sodium manganate (Na ₂ Mn ₃ O ₇ ).

  The metal titanate or the metal manganate is preferably in the form of powder having an average particle diameter in the range of 1 to 150 μm. Here, the average particle diameter can be measured by, for example, a laser diffraction type particle size distribution analyzer.

When the average particle diameter of the metal titanate is in the range of 1 to 150 μm, the adsorption capacity is high and the handling property in the granulation step is excellent. That is, if the average particle size is 1 μm or more, there is no production difficulty such as scattering or adhesion of a container due to static electricity, and if the average particle size is 150 μm or less, the adsorption capacity decreases due to a decrease in specific surface area. Nothing to do.
Therefore, in the present invention, it is preferable to use a metal titanate having such a particle size. The average particle size of the metal titanate is more preferably 4 to 50 μm.

  The metal titanate may be used alone or in combination of two or more.

  As for the metal manganate, as in the case of the metal titanate, if the average particle diameter is 1 to 150 μm, the handleability and the purification performance are excellent. The average particle size of the metal manganate is particularly preferably from 4 to 150 μm.

  The metal manganate may be used alone or in combination of two or more.

  Depending on the quality of the water to be treated, one or more of the metal titanates and one or more of the metal manganates may be used as a mixture. The metal salt and the metal manganate are used without being mixed.

<Glass frit>
The present invention is characterized in that a glass frit is used as a binder.
The raw material of the glass frit is not particularly limited. From the viewpoint of low-temperature sintering, it is desirable to use a glass frit having a softening point of 300 to 800 ° C, particularly 500 to 650 ° C.
Further, from the viewpoint of handling properties in the granulation step, it is preferable to use a glass frit having an average particle diameter of 0.1 μm or more, while, on the other hand, a viewpoint of efficiently contacting the water to be treated and the purification material for water treatment. More preferably, the average particle size of the glass frit is 50 μm or less. If the particle size of the glass frit is too large, the specific surface area occupied by the glass frit may be small, and the metal titanate or the metal manganate may not be sufficiently bound.
A more preferred average particle size of the glass frit is 0.5 to 20 μm.

  As the glass frit, only one kind may be used, or two or more kinds having different average particle diameters, glass compositions, softening points and the like may be mixed and used.

  The glass frit as the binder is preferably used at a ratio of 5 to 40% by mass, particularly 10 to 20% by mass based on the metal titanate or the metal manganate. If the added amount of the glass frit is small, the strength of the obtained purifying material tends to be insufficient, and if it is too large, the content of the metal titanate or the metal manganate relatively decreases, and the purifying performance tends to decrease. It is in.

<Water-soluble polymer>
The water-soluble polymer functions as a plasticizer. In the present invention, examples of the water-soluble polymer include carboxymethylcellulose (CMC), sodium polyacrylate, polyacrylic acid, polyethylene glycol, polyvinyl alcohol (PVA), and polyvinylpyrrolidone. One or two types such as (PVP) can be used. Of these, carboxymethylcellulose is preferably used from the viewpoint that a large amount of water can be contained.

  The water-soluble polymer is preferably used in an amount of 0.5 to 5% by mass, particularly 1 to 3% by mass, based on the metal titanate or the metal manganate. When the amount of the water-soluble polymer is within the above range, excellent granulation moldability can be obtained.

<Mixing / granulation process>
In the present invention, a predetermined amount of a glass frit and a water-soluble polymer are added to a metal titanate or a metal manganate, and water is further added and kneaded, and the obtained kneaded product is granulated.
Here, the addition amount of water is preferably 30 to 70% by mass, particularly 40 to 60% by mass based on the metal titanate or the metal manganate, in order to obtain excellent kneading properties and granulation moldability. preferable.

  In this kneading, additives other than the glass frit and the water-soluble polymer, for example, a plasticizer such as starch, lactose, and alginic acid may be added as long as the object of the present invention is not impaired.

  As a method of kneading a metal titanate or a metal manganate, a glass frit, a water-soluble polymer, water, and other additives used as necessary, a sufficient shear force is applied during kneading to sufficiently Any method can be used as long as it can be uniformly kneaded, and there is no particular limitation, but kneading is preferably performed using a high-speed mixing fine granulator such as a Spartan luzer. Also, kneading and granulation can be performed simultaneously using an extrusion granulator.

  The method of granulating the mixture obtained in the above kneading step is not particularly limited, and is performed by a rolling granulation method, or a columnar granulation using an extrusion granulator, and then a molding machine such as a marmerizer. Extrusion granulation method of forming into a sphere by using a method. In particular, the extrusion granulation method is preferable from the viewpoint of increasing the density of the granulated material.

The shape of the granulated product obtained by granulation is preferably spherical, but may be columnar, disk-shaped, or another shape.
The average particle size of the granulated product is preferably 150 to 3000 µm, more preferably 300 to 2000 µm. If the size of the granulated material is larger than the above range, the surface area is reduced, so that the purification performance is reduced.If the size is small, leakage from a strainer such as an adsorption tower or a differential pressure of the adsorption tower increases. There is a possibility that.
Here, the particle diameter of the granulated material corresponds to the diameter of the granulated material if the granulated material is spherical, and refers to the diameter of a sphere having the same volume as the granulated material when the granulated material has another shape.

  Further, it is preferable that the granulated material has a small particle diameter variation and a uniform particle diameter, and has a uniformity coefficient (in the particle size accumulation curve of the sample, the particle diameter of a sample through which 60% of all the samples pass). The ratio of the particle size of the sample through which 10% passes) is 2 or less, particularly preferably 1 to 1.5. In order to obtain a granulated product having a small uniformity coefficient as described above, the granulated product obtained by granulation may be subjected to a classification and sizing step of classifying and sizing according to a conventional method before or after drying. preferable.

<Drying process>
In the present invention, prior to firing the granulated product obtained in the granulation step, it is preferable to perform drying to volatilize and remove water in the granulated product, and the drying is performed using a hot-air dryer or the like. It is preferable to carry out at 50 to 150 ° C. for about 1 to 24 hours.

<Baking process>
It is preferable that the dried granules are degreased by pre-firing prior to firing to remove a part of the water-soluble polymer in the granules by oxidative decomposition.
This degreasing step is preferably performed at 200 to 400 ° C. for about 1 to 5 hours.

The temperature of the firing step varies depending on the softening point of the glass frit to be used, but the softening point of the glass frit or a temperature higher than the softening point, preferably a temperature range from the softening point of the glass frit to the softening point of the glass frit + 100 ° C, for example, softening It is preferable that the temperature is from + 1 ° C to softening point + 80 ° C, particularly from + 1 ° C to + 50 ° C.
If the firing temperature is lower than the lower limit (less than the softening point of the glass frit), the glass frit may not be sufficiently sintered to obtain a high-strength purification material for water treatment. If the firing temperature is higher than the above upper limit, there is a possibility that the purification component may be thermally degraded.

  The firing time varies depending on the firing temperature, but is preferably about 0.5 to 24 hours in order to sufficiently sinter the glass frit and obtain a high-strength purifying material without impairing the production efficiency.

  The firing means is not particularly limited, and it is preferable to perform firing while supplying an oxygen-containing gas using an electric tunnel furnace, a gas-fired tunnel furnace, a batch kiln, or the like, and in particular, an electric tunnel furnace is preferable. It is.

<Purification materials for water treatment>
The purification material for water treatment of the present invention produced using a glass frit as a binder shows sufficient mechanical strength by sintering the glass frit without impairing the original purification performance of the metal titanate or the metal manganate. At the same time, the bulk density can be increased by its low swelling property, and the packing density in an adsorption tower or the like can be increased to exhibit high purification performance.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Raw materials used in the following Examples and Comparative Examples are as follows.
<Metal titanate>
Potassium dititanate having an average particle size of 20 μm

<Glass frit>
Glass frit A: average particle size 5 μm, softening point 555 ° C.
Glass frit B: average particle size 2.6 μm, softening point 565 ° C.
Glass frit C: average particle size 3.3 μm, softening point 649 ° C.
Glass frit D: average particle size 4.6 μm, softening point 375 ° C.

<Water-soluble polymer>
Carboxymethyl cellulose (CMC)
Polyvinyl alcohol (PVA)

<Clay mineral>
Attapulgite

  Further, the following (1) to (3) were evaluated for the purifying materials for water treatment obtained in the following Examples and Comparative Examples.

(1) Strength In the activated carbon test method described in JIS K1474, those with a hardness of 90% or more were judged to have a sufficient strength of “」 ”, and those with a hardness of less than 90% were judged to have an insufficient strength of“ X ”.

(2) Bulk Density 10 mL of a water treatment purification material swollen in water was sampled, dried at 110 ° C. for 2 hours to completely remove water, and its mass W (g) was measured. Was used to determine the bulk density (g-dry / mL).
The larger the bulk density, the harder it is to swell.
Further, the increase rate (%) with respect to the bulk density of the purification material for water treatment of Comparative Example 1 was calculated.

(3) Adsorption test Using test water to which NaOH was added at an Sr concentration of 100 mg / L and an NaCl concentration of 10 g / L to obtain an equilibrium pH 12, a purification material for water treatment was used so that the liquid-solid ratio became 100 mL / g-dry. A batch test was carried out by adding (purification material for water treatment 1 g-dry to 100 mg / L of test water) and shaking for 3 days. The water treatment purification material used was a material swelled in a sufficient amount of water.
The Sr concentration in the test water at the time of reaching the equilibrium is C _eq [μg-Sr / mL], and the Sr adsorption amount (saturated adsorption amount) per unit mass of the purification material for water treatment at this time is q _eq [μg-Sr / g]. The partition coefficient K _d [mL / g] was determined from the following equation.
K _d = q _eq / C _eq
The larger the partition coefficient, the better the adsorption performance.

<Example 1>
To 200 g of potassium dititanate, 40 g of glass frit A and 10 g of CMC were added and mixed, and about 100 g of water was added and kneaded.
This kneaded product was extruded and granulated using a die having a die diameter of 0.7 mmφ, and subjected to sizing and classification to obtain a spherical or columnar granulated product having an average particle size of about 700 μm.
The obtained granules were dried at 140 ° C. for 3 hours to remove water, subjected to a degreasing step at 300 ° C. for 2 hours, and then calcined at 600 ° C. for 12 hours to obtain a purification material for water treatment.

  The obtained purification materials for water treatment were evaluated in the above (1) to (3), and the results are shown in Table 1.

<Example 2>
Production and evaluation of a water treatment purifying material were carried out and evaluated in the same manner as in Example 1 except that the glass frit B was used in place of the glass frit A and the firing conditions were set at 600 ° C. for 8 hours. The results are shown in Table 1. Was.

<Example 3>
Except that glass frit C was used instead of glass frit A, and that the firing conditions were 650 ° C. for 2 hours, a purification material for water treatment was produced and evaluated in the same manner as in Example 1, and the results are shown in Table 1. Was.

<Example 4>
Production and evaluation of a water treatment purifying material were performed in the same manner as in Example 1 except that the glass frit D was used instead of the glass frit A and the firing conditions were set at 400 ° C. for 2 hours. The results are shown in Table 1. Was.

<Comparative Example 1>
Attapulgite was used in place of glass frit A, and about 120 g of a 7% by mass aqueous solution of PVA was added and kneaded instead of CMC and water. The water treatment was performed in the same manner as in Example 1 except that the firing conditions were set at 800 ° C. for 2 hours. The production and evaluation of the cleaning material were performed, and the results are shown in Table 1.

  From Table 1, according to the present invention, the bulk density can be increased as compared with a conventional water treatment purifying material using a clay mineral as a binder, and the purifying performance per unit volume can be improved. Since low-temperature sintering is possible, it can be seen that thermal degradation of the purification component can be prevented and the purification performance per unit mass can be improved.

Claims (10)

  A method for producing a purification material for water treatment, comprising mixing and granulating a metal titanate or a metal manganate, a glass frit and a water-soluble polymer, and firing the granulated material.   The method for producing a purification material for water treatment according to claim 1, wherein the water-soluble polymer is carboxymethyl cellulose.   The mixing amount of the glass frit with respect to the metal titanate or the metal manganate is 5 to 40% by mass, and the mixing amount of the water-soluble polymer is 0.5 to 5% by mass. 3. The method for producing a purification material for water treatment according to claim 1.   The method for producing a purification material for water treatment according to any one of claims 1 to 3, wherein an average particle diameter of the granulated material is 150 to 3000 µm.   The method for producing a purification material for water treatment according to any one of claims 1 to 4, wherein the granulated material is fired at a temperature equal to or higher than the softening point of the glass frit.   A purification material for water treatment, comprising a mixture of a metal titanate or a metal manganate, a glass frit and a water-soluble polymer, and a calcined product of a granulated product.   The purification material for water treatment according to claim 6, wherein the water-soluble polymer is carboxymethyl cellulose.   The ratio of the glass frit to the metal titanate or the metal manganate is 5 to 40% by mass, and the ratio of the water-soluble polymer is 0.5 to 5% by mass. Purification material for water treatment.   The purification material for water treatment according to any one of claims 6 to 8, wherein the average particle diameter of the granulated product is 150 to 3000 µm.   The purification material for water treatment according to any one of claims 6 to 9, wherein the softening point of the glass frit is 300 to 800 ° C.