JP2017013034A - Adsorbent and production method thereof - Google Patents

Abstract

An adsorbent suitable for use in adsorbing and removing strontium contained in water is provided. The strontium adsorbent of the present invention has amorphous barium aluminosilicate. The strontium adsorbent of the present invention preferably has a BET specific surface area of 2 m 2 / g or more and 250 m 2 / g or less. The amorphous barium aluminosilicate has a molar ratio SiO2 / Al2O3 in the composition analysis of 1.5 or more and 3.5 or less, BaO / Al2O3 of 0.8 or more and 1.5 or less, and A2O / BaO of 0.8. It is also preferable that it is 01 or more and 0.3 or less. [Selection] Figure 1

Description

  The present invention relates to an adsorbent suitably used for adsorption removal of strontium contained in water and a method for producing the same.

As a method for treating a waste liquid containing a radioactive substance, a treatment method for adsorbing and removing a radionuclide with an inorganic adsorbent, an ion exchange resin, or the like is known. As an adsorption method using an inorganic adsorbent, for example, the following method is known.
(1) A method using a titanium silicate compound, titanic acid, titanate, and a zeolite compound (Patent Document 1 below).
(2) A method using manganese dioxide as an adsorbent (Patent Document 2 below).

Regarding the removal of strontium, the following methods are known.
(1) A method of removing an aqueous solution containing strontium by bringing it into contact with a perovskite type compound containing titanium or niobium (Patent Document 3 below).
(2) A method of removing radioactive strontium from a waste liquid using a solid material in which any one of calcium carbonate, strontium carbonate, and barium carbonate is occluded (Patent Document 4 below).
(3) A method of adsorbing strontium contained in seawater using A-type zeolite or X-type zeolite encapsulated with a calcium alginate membrane (Patent Document 5 below).

JP 2014-029269 A Japanese Patent Laid-Open No. 4-86599 JP 2005-230664 A Japanese Patent Laid-Open No. 2002-267996 JP 2013-174578 A

  However, the seawater contains much more cognate ions (calcium and magnesium) than strontium. Therefore, in the conventional technology, it is difficult to efficiently separate and adsorb strontium from seawater due to the influence of coexisting calcium and magnesium.

  An object of the present invention is to provide a strontium adsorbent and a method for producing the same, which can eliminate the various disadvantages of the above-described prior art.

  The present invention provides a strontium adsorbent containing amorphous barium aluminosilicate.

The present invention also provides a method for producing the adsorbent as described above.
A silicon source, an aluminum source, a barium source, and water are mixed so that a mixed solution having a composition represented by the molar ratio shown below is obtained, and the obtained mixed solution is heated to a temperature of 5 ° C. or higher and 50 ° C. or lower. The manufacturing method of a strontium adsorbent which has the process hold | maintained in this is provided. In the following formula, A is an alkali metal.
SiO ₂ / Al ₂ O ₃ is 1.0 or more and 3.0 or less BaO / Al ₂ O ₃ is 0.5 or more and 2.0 or less A ₂ O / BaO is 1.0 or more and 3.2 or less

  According to the present invention, an adsorbent capable of efficiently adsorbing and removing strontium contained in water, particularly seawater is provided. Further, according to the present invention, this adsorbent can be produced by an industrially advantageous method.

1 is an XRD diffractogram of barium aluminosilicate obtained in Example 1. FIG. FIG. 2 is an XRD diffractogram obtained by subjecting barium aluminosilicate obtained in Example 1 to an adsorption test using artificial seawater.

  The adsorbent of the present invention contains amorphous barium aluminosilicate. The adsorptive capacity of the adsorbent of the present invention is mainly derived from this amorphous barium aluminosilicate.

  In the present invention, barium aluminosilicate is amorphous when the barium aluminosilicate is measured by a powder X-ray diffraction method in the range of 2θ = 7 ° to 60 ° using Cu—Kα ray as a radiation source. This is confirmed by the fact that no diffraction peak derived from high quality barium aluminosilicate is observed. Amorphous barium aluminosilicate preferably exhibits a so-called halo peak in the measurement by the above powder X-ray diffraction method. The adsorbent containing amorphous barium aluminosilicate can be suitably obtained by the production method of the present invention described later.

  The present inventors presume the reason why the adsorbent of the present invention using amorphous barium aluminosilicate has high adsorption performance of strontium as follows. When amorphous barium aluminosilicate is in contact with seawater, barium ions in the amorphous structure react with sulfate ions in the seawater to produce solid barium sulfate. As a result, barium ions escape from the amorphous structure. In the amorphous structure, strontium ions are selectively adsorbed in seawater by selectively adsorbing barium ions and strontium ions close to the ion radius, which are the same divalent ions as barium ions, in the voids where barium ions have escaped. It is thought that it is removed by adsorption. The inventors found that the barium ions are more easily released from the barium aluminosilicate than the crystalline one because the barium aluminosilicate is amorphous, and this is the reason why the adsorption performance of the adsorbent of the present invention is high. I guess that is. According to the X-ray diffraction analysis as described later, according to the X-ray diffraction analysis, the adsorbent of the present invention expresses a barium sulfate crystal peak after strontium adsorption, which supports the aforementioned adsorption mechanism.

  As described above, since the amorphous barium aluminosilicate has reactivity with sulfate ions, the adsorbent of the present invention also has reactivity with sulfate ions. That the adsorbent has reactivity with sulfate ions can be confirmed by producing barium sulfate when the adsorbent is brought into contact with sulfate ions. For example, when 2.0 g of an adsorbent is put into 2000 ml of an aqueous solution containing sulfate ions in an amount of about 500 to 5000 ppm and stirred for 1 hour, and then powder X-ray diffraction measurement is performed using Cu-Kα rays as a radiation source In addition, it is preferable that the main peak of barium sulfate is observed. The main peak of barium sulfate is usually observed at a position of 2θ = 26 °. In addition, strong peaks are observed at 2θ = 29 ° and 43 °.

In addition, the adsorbent of the present invention may contain crystalline barium aluminosilicate in addition to amorphous barium aluminosilicate, as long as the effects of the present invention are not impaired. However, it is preferable that the adsorbent of the present invention does not substantially contain crystalline barium aluminosilicate. For example, the amount of crystalline barium aluminosilicate contained in the adsorbent of the present invention is preferably 3 parts by mass or less with respect to 100 parts by mass of amorphous barium aluminosilicate, and 2 parts by mass or less. More preferably. The amount ratio between crystalline barium aluminosilicate and amorphous barium aluminosilicate is the maximum intensity (cps) of the halo peak of amorphous aluminosilicate barium observed at 2θ = 20 to 37 ° in XRD diffraction analysis, In some cases, it can be estimated by the ratio of the diffraction intensity to the quality barium aluminosilicate. For example, when the adsorbent has a G-type zeolite represented by the general formula “BaAl ₂ Si ₃ O ₁₀ .nH ₂ O”, the diffraction at 2θ = 22.5 ° which is the strongest peak of the G-type zeolite. It can be estimated using the ratio of the maximum intensity to the intensity.

From the above viewpoint, the adsorbent of the present invention is derived from crystalline barium aluminosilicate when powder X-ray diffraction measurement is performed in the range of 2θ = 7 ° to 60 ° using Cu—Kα ray as a radiation source. It is preferable not to show a specific diffraction peak, and it is more preferable not to show a diffraction peak derived from crystalline aluminosilicate. The specific diffraction peak derived from crystalline barium aluminosilicate is, for example, 11.7 °, 13.0 derived from G-type zeolite represented by the general formula “BaAl ₂ Si ₃ O ₁₀ .nH ₂ O”. The peaks at °, 22.5 °, 25.5 °, 26.8 °, 27.6 °, 29.0 °, 30.6 °, 33.3 ° and 40.5 ° can be mentioned. Specific diffraction peaks derived from crystalline aluminosilicates other than crystalline barium aluminosilicate include 7.0 °, 10.0 °, 12.3 ° derived from sodium aluminosilicate (A-type zeolite), Peaks of 16.0 °, 21.6 °, 23.8 °, 27.0 °, 29.8 ° and 34.1 ° can be mentioned.

  The measurement conditions of the above-mentioned powder X-ray diffraction method can be set as follows, for example. In other words, the device name: D8 AdvanceS and the manufacturer: Bruker are used as measuring instruments. The target Cu, the source Cu-Kα, the tube voltage 40 kV, the tube current 40 mA, the scanning speed 0.1 ° / sec, and the reading width 0.02 °.

Examples of the amorphous barium aluminosilicate used in the present invention include a barium salt represented by the general formula (1): xBaO.yAl ₂ O ₃ .zSiO ₂ .nH ₂ O. Here, x, y, and z represent numbers greater than 0, and n represents a number greater than or equal to 0.

The amorphous barium aluminosilicate used in the present invention has a molar ratio when the composition is analyzed from the viewpoint of enhancing the effect of the present invention and the ease of production of the amorphous barium aluminosilicate. it is preferable SiO ₂ / Al ₂ O ₃ is 1.5 to 3.5. From the above viewpoint, the molar ratio SiO ₂ / Al ₂ O ₃ is more preferably 1.7 or more and 2.8 or less, and particularly preferably 1.8 or more and 2.3 or less.

When the composition of the amorphous barium aluminosilicate used in the present invention is analyzed, the molar ratio BaO / Al ₂ O ₃ is 0.8 or more, and the amount of barium in the amorphous barium aluminosilicate is constant. It is preferable from the viewpoint that the effects of the present invention can be more easily obtained by setting the amount to be equal to or more than the above amount. Further, the molar ratio BaO / Al ₂ O ₃ of the amorphous barium aluminosilicate is preferably 1.5 or less from the viewpoint of easy production of the amorphous barium aluminosilicate. From these viewpoints, the molar ratio BaO / Al ₂ O ₃ is preferably 0.8 or more and 1.5 or less, more preferably 0.85 or more and 1.3 or less, and 0.9 or more and 1.2 or less. It is particularly preferred that

From the viewpoint of making each of the above molar ratios in the above range, and from the viewpoint of making it easier to produce the amorphous barium aluminosilicate used in the present invention, when analyzing the composition of the amorphous barium aluminosilicate used in the present invention The content of SiO ₂ is preferably 20% by mass or more and 40% by mass or less, more preferably 22% by mass or more and 38% by mass or less,
It is particularly preferably 23% by mass or more and 36% by mass or less.

From the viewpoint of making each of the above molar ratios in the above range, and from the viewpoint of making it easier to produce the amorphous barium aluminosilicate used in the present invention, when analyzing the composition of the amorphous barium aluminosilicate used in the present invention The content of Al ₂ O ₃ is preferably 14% by mass or more and 28% by mass or less, more preferably 16% by mass or more and 26% by mass or less, and 18% by mass or more and 24% by mass or less. Is particularly preferred.

  From the viewpoint of making each of the above molar ratios in the above range, and from the viewpoint of making it easier to produce the amorphous barium aluminosilicate used in the present invention, when analyzing the composition of the amorphous barium aluminosilicate used in the present invention The content of BaO is preferably 20% by mass or more and 40% by mass or less, more preferably 25% by mass or more and 40% by mass or less, and particularly preferably 27% by mass or more and 40% by mass or less. .

The amount of H ₂ O in the amorphous barium aluminosilicate composition used in the present invention may depend on the storage conditions of the amorphous barium aluminosilicate, and is, for example, 5% by mass or more and 20% by mass or less. It is preferably 8% by mass or more and 18% by mass or less, more preferably 10% by mass or more and 16% by mass or less.

In order to set the molar ratio of SiO ₂ / Al ₂ O ₃ and BaO / Al ₂ O ₃ within the above range, or to set the content of SiO ₂ , Al ₂ O ₃ , BaO and H ₂ O within the above range, What is necessary is just to manufacture the adsorbent of this invention by the method as described in the Example mentioned later. The content of SiO ₂ and Al ₂ O ₃ , BaO and H ₂ O in the aluminosilicate barium is measured by ICP emission spectroscopic analysis (ICP-AES), specifically by the method of the examples described later.

Examples of the molar ratio of SiO ₂ / Al ₂ O ₃ and BaO / Al ₂ O ₃ and the contents of SiO ₂ , Al ₂ O ₃ , BaO and H ₂ O in the adsorbent itself of the present invention are amorphous. Ranges similar to the ranges listed above as the molar ratio of SiO ₂ / Al ₂ O ₃ and BaO / Al ₂ O ₃ and the contents of SiO ₂ , Al ₂ O ₃ , BaO and H ₂ O in the aluminosilicate barium Is mentioned.

The amorphous barium aluminosilicate used in the present invention may contain a certain amount of alkali metal such as sodium and / or potassium. For example, when amorphous barium aluminosilicate contains a certain amount of alkali metal, this alkali metal may be present at the cation site instead of barium in the structure of amorphous barium aluminosilicate. Therefore, the amorphous barium aluminosilicate used in the present invention is partly or wholly represented by the general formula (1 ′): xBaO · wA ₂ O · yAl ₂ O ₃ · zSiO ₂ · nH ₂ O An alkali metal composite aluminosilicate may be used. A in the general formula (1 ′) is an alkali metal, and w is a number greater than 0 and less than x. The definitions of x, y, z and n in the general formula (1 ′) are the same as described above.

  In this specification, the amorphous barium aluminosilicate including the amorphous composite aluminosilicate represented by the general formula (1 ′) is referred to. Examples of the amorphous composite aluminosilicate include amorphous barium sodium aluminosilicate, amorphous potassium potassium aluminosilicate, amorphous potassium potassium aluminosilicate, and the like.

When the amorphous barium aluminosilicate used in the present invention contains an alkali metal as described above, the amount of alkali metal in the amorphous barium aluminosilicate is not more than a certain amount, so that the barium aluminosilicate is stable. From the viewpoint of easily maintaining an amorphous state. From this viewpoint, the molar ratio A ₂ O / BaO measured by composition analysis is preferably as low as about 0.3 or less, more preferably 0.1 or less, and even more preferably 0.08 or less. Is particularly preferably 0.06 or less.

Further, the amorphous barium aluminosilicate used in the present invention is better as the molar ratio A ₂ O / BaO measured by composition analysis is lower, but the lower limit is 0.01 or more. The amorphous barium aluminosilicate used in the present invention is preferable from the viewpoint of easy production. From these viewpoints, the molar ratio A ₂ O / BaO is preferably 0.01 or more, more preferably 0.015 or more, and particularly preferably 0.02 or more.

From the viewpoint of making each of the above molar ratios in the above range, and from the viewpoint of making it easier to produce the amorphous barium aluminosilicate used in the present invention, when analyzing the composition of the amorphous barium aluminosilicate used in the present invention The content of A ₂ O is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.05% by mass or more and 4.5% by mass or less, and more preferably 0.1% by mass or more. It is especially preferable that it is 4.0 mass% or less.

In order to make the contents of the molar ratios A ₂ O / BaO and A ₂ O within the above ranges, the adsorbent of the present invention may be produced by the production method described later. For example, when sodium is used as the alkali metal in the production method described later, A ₂ O is exclusively Na ₂ O. From this viewpoint, the preferable range of the Na ₂ O content of the amorphous barium aluminosilicate contained in the adsorbent of the present invention is the same range as the preferable range of the A ₂ O content. Similarly, the preferable range of the K ₂ O content of amorphous barium aluminosilicate is the same range as the preferable range of the A ₂ O content.

The contents of A ₂ O, Na ₂ O and K ₂ O are measured by ICP emission spectroscopic analysis (ICP-AES), specifically by the method of Examples described later.
Examples of the molar ratio A ₂ O / BaO and the contents of A ₂ O, Na ₂ O and K ₂ O in the adsorbent itself of the present invention include molar ratios A ₂ O / BaO in amorphous barium aluminosilicate. In addition, examples of the content of A ₂ O, Na ₂ O, and K ₂ O include the same ranges as the above-described ranges.

The BET specific surface area of the amorphous barium aluminosilicate used in the present invention is preferably 2 m ² / g or more from the viewpoint of improving the strontium adsorption performance. As described above, when amorphous barium aluminosilicate is in contact with seawater, barium ions in the amorphous structure react with sulfate ions in seawater to produce solid barium sulfate. As a result, the inventors speculate that strontium ions, which are the same divalent ions as barium ions, are selectively adsorbed in the voids after the barium ions escape from the amorphous structure. Therefore, by using the adsorbent having a higher specific surface area as the adsorbent of the present invention, the reactivity with sulfate ions in water can be improved and the strontium adsorption performance can be improved. Specifically, from the viewpoint of improving the strontium adsorption performance, the BET specific surface area of the amorphous barium aluminosilicate in the present invention is preferably 80 m ² / g or more, more preferably 85 m ² / g or more, It is particularly preferably 90 m ² / g or more. The BET specific surface area of the amorphous barium aluminosilicate in the present invention is preferably as large as possible, but is preferably 250 m ² / g or less from the viewpoint of the production cost of the amorphous barium aluminosilicate. From this viewpoint, the BET specific surface area of the amorphous barium aluminosilicate is preferably 250 m ² / g or less, and more preferably 200 m ² / g or less. In addition, as a preferable range of the BET specific surface area of the adsorbent itself of the present invention, the same numerical range as the above-described numerical ranges can be given as a preferable range of the BET specific surface area of amorphous barium aluminosilicate.

  In order to produce amorphous barium aluminosilicate having a BET specific surface area in the above range, the adsorbent of the present invention may be produced by the production method described later, and the use ratio of each raw material may be adjusted at that time. . The BET specific surface area is measured by the BET single point method. Specifically, it measures by the method as described in the Example mentioned later.

The form of the adsorbent of the present invention is, for example, a powder. The term “powder” as used herein includes a powdery body and a granular body. The granular material includes, for example, a columnar shape and a spherical shape.
The adsorbent of the present invention is preferably a granule having a particle size of 2 μm or more and 2000 μm or less because it can be suitably used for strontium adsorption in water, particularly in seawater. In particular, it is preferable that the adsorbent of the present invention has a particle size of 200 μm or more and 2000 μm or less because it is suitable as an adsorbent for use in filling an adsorption tower. When the particle size is 200 μm or more, when the adsorbent of the present invention is packed in the adsorption tower and passed through, the particles are hardly clogged in the adsorption tower, and pressure loss can be prevented from increasing in the adsorption tower. Further, when the particle size is larger than 2000 μm, the adsorption rate of strontium is slowed and the adsorption efficiency is deteriorated. By making the particle size 2000 μm or less, the adsorption performance can be improved. From such a viewpoint, the particle size of the adsorbent of the present invention is more preferably 300 μm or more and 1000 μm or less. Specifically, it can be confirmed that the particle size of the adsorbent of the present invention is in a specific range by using a sieve having an opening corresponding to each particle size according to the JIS Z8801 standard, and 98% by mass or more of the adsorbent of the present invention. When the mesh size passes through a 2 mm sieve and 98% by mass or more does not pass through a sieve having an aperture of 212 μm, the particle size is 200 μm or more and 2000 μm or less. Further, when 98% by mass or more of the adsorbent of the present invention passes through a sieve having an aperture of 1000 mm and 98% by mass or more does not pass through a sieve having an aperture of 300 μm, the particle size is assumed to be 300 μm or more and 1000 μm or less.

  Moreover, it is also preferable to use the adsorbent of this invention with the form fixed to the nonwoven fabric as a form of a powdery body so that it may mention later. In this case, the particle size of the adsorbent is preferably an average particle size of 2 μm or more and 10 μm or less from the viewpoint that the pulverization step can be easily performed in the production process of the adsorbent, and the maximum particle size is 100 μm or less. It is preferable from the viewpoint that the adsorbent particles can be prevented from falling off from the nonwoven fabric when fixed to the nonwoven fabric. From these viewpoints, the particle size of the powdery adsorbent when used fixed to a non-woven fabric is more preferably an average particle size of 2.5 to 20 μm and a maximum particle size of 96 μm or less. The average particle diameter here is specifically the particle diameter (D50) at which the integrated volume from the small particle diameter side by the laser diffraction / scattering particle size distribution measurement method is 50%, and the maximum particle diameter is the same measurement. The particle size (D100) at which the cumulative volume from the small particle size side by the method becomes 100%. Specifically, the average particle size and the maximum particle size can be measured with a laser diffraction / scattering particle size distribution measuring apparatus (Nikkiso Microtrac).

  The adsorbent of the present invention may be composed only of amorphous barium aluminosilicate, and may contain other components in addition to amorphous barium aluminosilicate. The preferable content of amorphous barium aluminosilicate in the adsorbent of the present invention varies depending on its form. For example, when the adsorbent is used while being fixed to a nonwoven fabric, the amount of amorphous barium aluminosilicate in the adsorbent is preferably 90% by mass or more, and particularly preferably 95% by mass or more. When the adsorbent is granulated with a binder, the amount of amorphous barium aluminosilicate in the adsorbent is preferably 70% by mass or more, particularly preferably 80% by mass or more. When the adsorbent contains a binder, the amount of the binder is preferably about 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of amorphous barium aluminosilicate.

The adsorbent of the present invention can be suitably produced by the following production method.
A silicon source, an aluminum source, a barium source, and water are mixed so that a mixed solution having a composition represented by the molar ratio shown below is obtained, and the obtained mixed solution is heated to a temperature of 5 ° C. or higher and 50 ° C. or lower. The manufacturing method which has the process hold | maintained. In the following formula, A is an alkali metal.
SiO ₂ / Al ₂ O ₃ is 1.0 or more and 3.0 or less BaO / Al ₂ O ₃ is 0.5 or more and 2.0 or less A ₂ O / BaO is 1.0 or more and 3.2 or less

The above molar ratio is preferable from the viewpoint of successfully producing the adsorbent of the present invention. In addition, the molar ratio SiO ₂ / Al ₂ O ₃ in the mixed solution is a certain value or more, the particle size of the obtained powder can be a certain value or more, and the powder can be handled in a subsequent process (for example, a filtration process). It is also preferable from the viewpoint of ease. In addition, it is preferable that the molar ratio SiO ₂ / Al ₂ O ₃ is not more than a certain value from the viewpoint of preventing mixing of aluminosilicate crystals other than amorphous barium aluminosilicate. The molar ratio BaO / Al ₂ O ₃ in the mixed solution is preferably a certain value or more from the viewpoint of easily obtaining a high-performance adsorbent, and the molar ratio BaO / Al ₂ O ₃ is a certain value or less. The amount of the soluble barium salt remaining in the mother liquor is preferably controlled from the viewpoint of reducing the burden on the wastewater treatment of the soluble barium salt by controlling it to a certain amount or less. In addition, it cannot be overemphasized that what was manufactured except the method is also contained in the adsorption agent of this invention, for example, each molar ratio may be outside the said range.

  The silicon source is preferably a water-soluble silicate in order to facilitate the reaction even at a low reaction temperature, and examples thereof include sodium silicate and potassium silicate. These silicon sources can be used alone or in combination of two or more. Of these silicon sources, use of sodium silicate is preferable from the viewpoint of industrial practicality because it is a solution and has good reactivity with the aluminum source and is inexpensive.

  As the aluminum source, for example, a water-soluble aluminum-containing compound can be used. Specific examples of the water-soluble aluminum-containing compound include sodium aluminate, aluminum nitrate, aluminum sulfate, and potassium aluminate. These aluminum sources can be used alone or in combination of two or more. Of these aluminum sources, it is preferable to use sodium aluminate from the viewpoint that it is a solution and therefore has good reactivity with the silicon source and facilitates production of the aluminosilicate.

  Examples of the barium source include water-soluble barium salts. Examples of such barium salts include barium chloride, barium nitrate, barium hydroxide, and barium acetate. These barium sources can be used alone or in combination of two or more. Among these barium sources, it is preferable to use barium hydroxide from the viewpoint of easy treatment of the waste liquid after ion exchange and from the viewpoint of increasing the specific surface area of the obtained amorphous aluminosilicate barium.

When, for example, sodium silicate is used as the silica source or when sodium aluminate is used as the aluminum source, sodium which is an alkali metal component contained therein is simultaneously regarded as NaOH and is also an alkali component. Thus, "A ₂ O" in the above molar ratio of the mixture "A ₂ O / BaO" unless otherwise indicated, are calculated as the sum of all the alkali component in the mixture, these silica source and aluminum source Of alkali components. In addition to or in place of the alkali component used as the silica source or the aluminum source, the present production method also includes a method using an alkali source such as caustic soda as necessary in order to adjust the molar ratio. However, in order to stably produce amorphous barium aluminosilicate, it is preferable not to use an alkali source other than the alkali source serving as the silica source and the aluminum source as much as possible.

  In the present production method, from the viewpoint of enhancing the performance of the adsorbent, the following ranges are preferable as the more preferable molar ratio in the mixed solution.

SiO ₂ / Al ₂ O ₃ is 1.3 or more and 2.7 or less BaO / Al ₂ O ₃ is 0.7 or more and 1.5 or less A ₂ O / BaO is 1.4 or more and 2.9 or less

In the present production method, from the viewpoint of enhancing the performance of the adsorbent, particularly preferable molar ratios in the mixed liquid include the following ranges.
SiO ₂ / Al ₂ O ₃ is 1.6 or more and 2.4 or less BaO / Al ₂ O ₃ is 0.8 or more and 1.2 or less A ₂ O / BaO is 1.8 or more and 2.6 or less

  The order of addition of each raw material to obtain a mixed liquid is as follows: a silicon-containing liquid obtained by mixing water and a silicon source, an aluminum-containing liquid obtained by mixing water and an aluminum source, and a water and barium source A method of preparing each of the barium-containing liquids obtained by mixing and mixing these three liquids is preferable from the viewpoint of easily obtaining the adsorbent of the present invention. When an alkali source such as caustic soda is further added, it may be added to any one of the above-mentioned three kinds of liquids, or two or more kinds of mixed liquids.

As a method of mixing the silicon-containing liquid, the aluminum-containing liquid, and the barium-containing liquid, for example, any of the following methods (1) to (3) can be adopted.
(1) Method of mixing silicon-containing liquid and barium-containing liquid, and mixing aluminum-containing liquid with the obtained mixed liquid (2) Mixing aluminum-containing liquid and barium-containing liquid, and silicon-containing liquid into the obtained mixed liquid (3) A method of mixing a silicon-containing liquid and an aluminum-containing liquid, and mixing a barium-containing liquid with the obtained mixed liquid

  When mixing two of the three liquids, it is preferable to add and mix one liquid over time with the other liquid. Similarly, when adding a mixed liquid obtained by mixing two liquids and the remaining one liquid, one liquid is added to the other liquid over time and mixed. Is preferred. The addition over time mentioned here includes, for example, dropwise addition at a rate of 15 minutes to 120 minutes. After mixing the two liquids, it is preferable to mix the third liquid after continuing stirring for 15 minutes to 120 minutes for the obtained liquid mixture.

  The liquid mixture obtained by mixing the silicon source, the aluminum source, the barium source, and water as described above is maintained at a constant temperature. From the viewpoint of preventing the appearance of the crystalline phase of alumino barium silicate and the viewpoint of stably obtaining amorphous barium aluminosilicate, this temperature (hereinafter also referred to as aging temperature) is preferably 50 ° C. or lower, and 45 ° C. More preferably, it is 40 ° C. or less. The lower limit of the aging temperature is not particularly limited, but for example, it is preferably room temperature (25) ° C. or higher.

On the assumption that the aging temperature is within the above range, it is preferably from 0.25 hours to 3 hours, more preferably from 0.5 hours to 1.0 hour.
The above temperature holding step (also referred to as aging step) can be performed under normal pressure. The aging step is preferably performed while stirring the mixed solution from the viewpoint of improving the quality of the adsorbent obtained.

  The barium source generally has low solubility in water. Therefore, when preparing the barium-containing aqueous solution, it is preferable to increase the solubility in water by heating the barium-containing aqueous solution to a certain temperature. As this heating temperature, about 30 degreeC or more and about 50 degrees C or less can be mentioned, for example. The aging temperature may be the same as or different from the heating temperature. In the case of being different, the aging temperature may be higher or lower than the heating temperature.

  The slurry after the ripening step is filtered by a conventional method, then washed with repulp, the obtained washed product is dried, and then the obtained dried product is pulverized to obtain an adsorbent in powder form. Drying is preferably performed at 100 ° C. to 120 ° C. for 1 hour to 24 hours.

When the adsorbent of the present invention obtained as described above is used for various adsorbing sheets and mats such as a nonwoven fabric, it is used by adding the material as it is as a powdery material. As a specific method for fixing the adsorbent to the nonwoven fabric, there is a method in which a powdered adsorbent is dispersed in water together with an emulsified resin binder, impregnated with the nonwoven fabric, and then dried. Examples of the resin binder include latex binder, polyacrylate, polymethacrylate, acrylate copolymer, methacrylate copolymer, styrene butadiene copolymer, styrene acrylic copolymer, ethylene vinyl acetate copolymer, and nitrile rubber. , Acrylonitrile butadiene copolymer, polyvinyl alcohol and the like. As the nonwoven fabric, for example, those composed of polyester and / or polyolefin fibers are used. Before fixing to the nonwoven fabric, it is preferable to adjust the particle size of the adsorbent to a range of the above average particle diameter of 2 μm to 10 μm as necessary.
Thus, the nonwoven fabric which apply | coated the adsorbent can be used suitably for water treatment, for example by setting it as the form wound by making the surface which apply | coated the adsorbent inside.

  When processing the adsorbent of this invention which is a powder form into a granular material, a binder is normally used. There is no restriction | limiting in particular as this binder. Either or both of an inorganic binder (hereinafter referred to as “inorganic binder”) and an organic binder (hereinafter referred to as “organic binder”) can be used.

  Examples of the inorganic binder include clay minerals such as sodium silicate, sodium aluminate, silica sol, alumina sol, titania sol, zirconia sol, bentonite and montmorillonite, and these can be used alone or in combination of two or more.

  Examples of the organic binder include cellulosic materials such as carboxymethyl cellulose and hydroxyethyl cellulose, and polymer materials such as polyethylene glycol and polyethylene oxide, which can be used alone or in combination of two or more.

  When these various binders are used to form the powdery adsorbent of the present invention into granules, the various binders are kneaded with a kneader or the like, then molded with an extrusion granulator or the like, dried, and necessary After firing according to the above, the particles may be sized to a predetermined particle size by a method such as grinding or crushing.

  The granular adsorbent obtained by granulating the powdery adsorbent obtained by the production methods (A) and (B) above is packed in an adsorption vessel or adsorption tower and contains a radioactive strontium water treatment system. It can be suitably used as an adsorbent. However, the present invention is not limited to this form, and the adsorbent of the present invention can be suitably used as an adsorbent for a water treatment system containing radioactive strontium as various forms such as fixing to a nonwoven fabric.

  Examples of the adsorption method using the adsorbent of the present invention include a method in which the adsorbent and strontium are contacted in the presence of sulfate ions. The liquid to be subjected to the adsorption treatment in this method preferably contains 50 ppm or more of sulfate ions.

  Hereinafter, the present invention will be described with reference to examples. Unless otherwise specified, “%” represents “mass%”. The evaluation apparatus and measurement conditions used in the examples are as follows.

<Evaluation equipment and measurement conditions>
X-ray diffraction: Device name: D8 AdvanceS, manufacturer: Bruker was used as a measuring instrument. Scanning range: 5 ° to 85 ° target Cu-Kα, tube voltage 40 kV, tube current 40 mA, scanning speed 0.1 ° / sec, reading width 0.02 °.
-BET specific surface area: Using Flowsorb II2300 manufactured by Shimadzu Corporation as a measuring device,
The BET one-point method was used.
ICP-AES: Varian 720-ES was used. In the compositional analysis, the measurement wavelength of Na was 589.592 nm, the measurement wavelength of Al was 396.153 nm, the measurement wavelength of Si was 251.612 nm, and the measurement wavelength of Ba was 455.404 nm. The standard samples used were aqueous solutions of Na, Al, Si, and Ba at concentrations of 10, 20, and 100 ppm, respectively.
In the adsorption test, the Sr concentration was measured by setting the Sr measurement wavelength to 216.596 nm. The standard sample used was an aqueous solution of artificial seawater with Ca 408.9 ppm and Sr 7.19 ppm.

Hereinafter, the following were used as a raw material for producing the aluminosilicate in Examples 1 to 7 and Comparative Example 1.
<Raw material>
No. 3 sodium silicate (Na ₂ O 9.2%, SiO ₂ 28.5%)
Sodium aluminate (Na ₂ O 19.0%, Al ₂ O ₃ 20.0%)
Barium hydroxide octahydrate (purity 99%)
25% aqueous sodium hydroxide solution

<Example 1>
Preparation of solution A: 51.0 g of sodium aluminate (Al ₂ O ₃ min: 0.1 mol) was mixed with 149 g of ion-exchanged water to make a total amount of 200 g.
Preparation of solution S: No. 3 sodium silicate 42.1 g (SiO ₂ min: 0.2 mol) was mixed with ion-exchanged water 157.9 g to make the total amount 200 g.
Preparation of liquid B: 31.5 g of barium hydroxide octahydrate (BaO content: 0.1 mol) was mixed with 468.5 g of ion-exchanged water to make a total amount of 500 g and dissolved by heating to 40 ° C.
A liquid containing a gel-like material was prepared by dripping and mixing the liquid S with liquid A over 30 minutes at room temperature. After completion of dropping, stirring was continued at 40 ° C. for 30 minutes. Next, B liquid was dripped over 30 minutes, and the mixed slurry was obtained. After completion of the dropwise addition, the mixed slurry was heated to 40 ° C. and stirring was continued for 30 minutes. The obtained slurry was filtered and repulp washed by a conventional method to obtain a solid, the obtained solid was dried at 115 ° C. for 4 hours, and the obtained dried was pulverized to prepare barium aluminosilicate.

<Example 2>
In Example 1, barium aluminosilicate was prepared in the same manner as in Example 1 except that the time during which stirring was continued at 40 ° C. was changed from 30 minutes to 80 minutes.

<Example 3>
In Example 1, barium aluminosilicate was prepared in the same manner as in Example 1 except that the time during which stirring was continued at 40 ° C. was changed from 30 minutes to 150 minutes.

<Examples 4 to 7>
In Example 1, barium aluminosilicate was used in the same manner as in Example 1 except that the amount of No. 3 sodium silicate in the S liquid was changed to the molar amount shown in Table 1 below as the SiO ₂ molar amount. Was prepared. However, the total amount of S liquid was kept at 200 g. This is because the amount of ion-exchanged water is increased or decreased to complement the amount of increase or decrease in the amount of sodium silicate.

<Comparative Example 1>
Preparation of solution S: 42.1 g of No. 3 sodium silicate (SiO ₂ min: 0.2 mol) was mixed with 32 g of 25% sodium hydroxide aqueous solution (Na ₂ O content: 0.1 mol) to further add 125.9 g of ion-exchanged water. To make the total amount 200 g.
Preparation of solution A: 51.0 g of sodium aluminate ((Al ₂ O ₃ min: 0.1 mol)) was mixed with 149 g of ion-exchanged water to make a total amount of 200 g.
A liquid containing a gel-like material was prepared by dripping and mixing the liquid S with liquid A over 30 minutes at room temperature. After completion of dropping, the mixture was heated to 40 ° C. and stirring was continued for 30 minutes. The obtained mixed slurry was filtered and repulp washed by a conventional method to obtain a solid, the obtained solid was dried, and the obtained dried was pulverized to prepare sodium aluminosilicate.

In Examples 1 to 7, each amount of SiO ₂ , Al ₂ O ₃ , BaO and Na ₂ O in the mixed slurry obtained by mixing the liquid A, liquid B and liquid S, and the molar ratio thereof “ Table 1 shows “SiO ₂ / Al ₂ O ₃ ”, “BaO / Al ₂ O ₃ ”, and “Na ₂ O / BaO”. The amounts of SiO ₂ , Al ₂ O ₃ and Na ₂ O in the mixed slurry of Comparative Example 1 and the molar ratio “SiO ₂ / Al ₂ O ₃ ” are shown in Table 1 below.

[Measurement and evaluation]
The following measurements and evaluations were performed for each sample of each example and comparative example.

<Aluminosilicate composition analysis>
Each 0.5 g of the aluminosilicate sample obtained in Examples 1 to 7 and Comparative Example 1 was dissolved in 100 ml of dilute nitric acid (5% strength aqueous solution). The obtained solution was subjected to ICP-AES analysis using the above measuring apparatus and conditions, and the amounts of Na, Si, Al, and Ba in each sample were measured, and Na ₂ O, SiO ₂ , Al ₂ O ₃ , and BaO, respectively. The content of Na ₂ O, SiO ₂ , Al ₂ O ₃ , and BaO was measured by converting to. Further, the content of H ₂ O was determined as “100% − (total amount of contents of Na ₂ O, SiO ₂ , Al ₂ O ₃ , BaO)”. The molar ratios “SiO ₂ / Al ₂ O ₃ ”, “BaO / Al ₂ O ₃ ”, and “Na ₂ O / BaO” in the aluminosilicate sample were determined from the obtained content results. The results are shown in Table 2 below. Moreover, the powder X-ray-diffraction measurement was performed about the aluminosilicate sample obtained in Examples 1-7 and the comparative example 1 with said measuring apparatus and conditions, and it was confirmed whether it was amorphous or crystalline. In the X-ray charts of barium aluminosilicate obtained in Examples 1 to 7 and Comparative Example 1, a halo peak was observed, a peak derived from aluminosilicate was not observed, and it was confirmed to be amorphous. An X-ray chart of the barium aluminosilicate sample obtained in Example 1 is shown in FIG. As shown in FIG. 1, in the chart of the barium aluminosilicate sample obtained in Example 1, the peak of barium carbonate, which is a byproduct, is observed, and the diffraction peak of barium aluminosilicate is not observed.
Moreover, the BET specific surface area was measured about the aluminosilicate sample obtained in Examples 1-7 and Comparative Example 1 with said measuring apparatus and conditions.
The results are shown in Table 2 below.

<Adsorption test>
After putting 0.1 g of the aluminosilicate sample obtained in each Example and each Comparative Example into 100 ml of artificial seawater (artificial seawater marine art SF-1 for test research, manufactured by Tomita Pharmaceutical Co., Ltd.) and stirring for 1 hour with a stirrer, ICP-AES analysis was performed on the Sr of the liquid using the measurement apparatus and conditions described above, and the Sr concentrations of the examples and the comparative examples were obtained. The Sr removal rate was calculated | required by obtaining ratio (%) with respect to Sr density | concentration in artificial seawater of the value which subtracted Sr density | concentration of each Example and the comparative example from Sr density | concentration in artificial seawater.
The content of the main components in an artificial sea water, NaCl; 22.1g / L, MgCl 2 · 6H 2 O; 9.9g / L (Mg: 1184ppm), CaCl 2 · 2H 2 O; 1.5g / L (Ca: 409 ppm), Na ₂ SO ₄ ; 3.9 g / L (SO ₄ : 2637 ppm), KCl; 0.61 g / L, SrCl ₂ ; 13 mg / L (Sr: 7.2 ppm).

The results of the above <Adsorption Test> are shown in Table 3 below.
Moreover, about the barium aluminosilicate obtained in Example 1, after using for an adsorption test, the powder X-ray-diffraction measurement was carried out on said conditions. The X-ray chart obtained by this is shown in FIG. As shown in Fig. 2, in the barium aluminosilicate chart after the adsorption test, a new diffraction peak of barium sulfate has appeared, and the sulfate ions in artificial seawater react with the barium ions of barium aluminosilicate to produce barium sulfate. It shows that.
Moreover, about the barium aluminosilicate obtained in Examples 2-7, when it used for the adsorption test, when the powder X-ray diffraction measurement was carried out, the diffraction peak of barium sulfate was confirmed.

  From the results of Table 3 above, it can be seen that the adsorbents of each example using amorphous barium aluminosilicate have a high strontium removal rate and excellent performance for adsorbing strontium. Compared with these, it turns out that the strontium adsorption | suction performance is significantly inferior in the comparative example 1 using amorphous sodium aluminosilicate. Thus, it is clear that amorphous barium aluminosilicate is suitable as a strontium adsorbent.

Claims (8)

  A strontium adsorbent containing amorphous barium aluminosilicate.   The strontium adsorbent according to claim 1, which has reactivity with sulfate ions. The strontium adsorbent according to claim 1 or 2, wherein the BET specific surface area is 2 m ² / g or more and 250 m ² / g or less. The strontium adsorbent according to claim 3, wherein the BET specific surface area is 80 m ² / g or more and 250 m ² / g or less. Amorphous barium aluminosilicate has a molar ratio SiO ₂ / Al ₂ O _{3 in} the composition analysis of 1.5 to 3.5 and a molar ratio BaO / Al ₂ O ₃ in the composition analysis of 0.8 to 1. The strontium adsorbent according to any one of claims 1 to 4, which is 5 or less. The amorphous barium aluminosilicate contains an alkali metal A, and the molar ratio A ₂ O / BaO in the composition analysis is 0.01 or more and 0.3 or less, according to any one of claims 1 to 5. Strontium adsorbent. A method for producing a strontium adsorbent according to claim 1,
A silicon source, an aluminum source, a barium source, and water are mixed so that a mixed solution having a composition represented by the molar ratio shown below is obtained, and the obtained mixed solution is heated to a temperature of 5 ° C. or higher and 50 ° C. or lower. The manufacturing method of a strontium adsorbent which has the process hold | maintained. In the following formula, A is an alkali metal.
SiO ₂ / Al ₂ O ₃ is 1.0 or more and 3.0 or less BaO / Al ₂ O ₃ is 0.5 or more and 2.0 or less A ₂ O / BaO is 1.0 or more and 3.2 or less   A method for adsorbing strontium, comprising contacting the strontium adsorbent according to any one of claims 1 to 6 with strontium in the presence of sulfate ions.