KR102446745B1 - A synthesis method of pollucite and a pollucite thereby - Google Patents

Abstract

The present invention relates to a method for synthesizing folucite as a method for immobilizing radioactive cesium and to a method for synthesizing folucite according to the method, comprising the steps of: (a) mixing natural zeolite and the cesium to produce a first mixture; and (b) heating the first mixture at 100°C or less.
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Description

Pollusite synthesis method and pollucite synthesized accordingly as a method for immobilizing radioactive cesium {A synthesis method of pollucite and a pollucite thereby}

The present invention relates to a method for synthesizing folucite as a method for immobilizing radioactive cesium, and to folucite synthesized by such a method for synthesizing folucite, wherein cesium is immobilized by synthesizing folucite through a hydrothermal synthesis reaction at a temperature of 200° C. or higher, but with hydrothermal boiling. Unlike the prior art, which required an iron pressure vessel due to the problem of .

Radioactive cesium-137, which is generated in large quantities from wastes after dismantling nuclear power plants as well as nuclear accidents such as the Fukushima nuclear power plant, has chemical properties similar to potassium, so it is known that the risk is very high because it can easily enter the human body and accumulate in the muscles. have. Cs-137 has a half-life of about 30 years, is highly soluble in water, and thus easily enters the human body.

After the Fukushima nuclear accident, various types of adsorbents have been developed to remove Cs-137, the most important nuclide. Recently, research has been conducted to prevent cesium from leaking from the perspective of long-term disposal through mineralization of cesium to immobilize Cs-137, rather than simply adsorbing Cs-137.

Among these, the most representative immobilization method of cesium is synthesis into pollucite. Polusite (Cs _(1-x) Na _(x) AlSi ₂ O ₆ , where 0<x<0.5) is in the form of an aluminosilicate mineral, and the leaching rate of cesium is low, so it is suitable for fixing radioactive cesium. As it is known as the most suitable mineral form, it is evaluated as the most suitable in terms of long-term disposal.

Initially, research technology for synthesizing folucite using high-temperature sintering was developed. However, since this method is performed under ultra-high temperature conditions of about 1000° C., cesium may be volatilized, which is somewhat difficult to apply to radioactive cesium. Afterwards, to compensate for this problem, the synthesis temperature of folucite was lowered to 200 to 300 °C through hydrothermal synthesis. .

However, this also has a limitation, since the hot water exceeds 100 °C, pressure must be applied to prevent boiling of the hot water, and for this purpose, a steel pressure vessel must be used.

That is, when the hydrothermal synthesis temperature exceeds 100°C, it is necessary to use a teflon-lined autoclave that applies pressure to prevent boiling of the hydrothermal water during the synthesis process due to the boiling point of water. It is not suitable for synthesizing folucite by treating cesium.

Only when the hydrothermal temperature condition is lowered to 100° C. or less in the synthesis process can radioactive cesium be treated in large quantities without additional pressure in the polucite synthesis process, and research on this is urgently needed.

(Patent Document 1) US05875407 B

(Patent Document 2) JP31152467 A

(Patent Document 3) KR10-1579795 B

In order to solve the problems of the prior art, as a method for immobilizing radioactive cesium, in order to solve the problem of boiling of hot water, a method for synthesizing folucite under atmospheric pressure conditions of 100° C. or less, and folucite synthesized by the method are proposed.

In order to solve the problems of the prior art, the method for synthesizing folucite according to the present invention is a method for immobilizing radioactive cesium. becoming a step; and (b) heating the first mixture at 100° C. or less.

Preferably, in step (a), sodium hydroxide (NaOH) may be further mixed to produce the first mixture.

Preferably, the first mixture in step (b) may be heated at 90 to 100 ℃.

Preferably, in step (b), the first mixture may be heated at 95 to 97°C.

Preferably, in step (b), the first mixture may include a step of heating under atmospheric pressure conditions.

Preferably, the step (a) comprises: (a-1) adding natural zeolite to deionized water; and (a-2) after the step (a-1), the cesium and the sodium hydroxide are added to the deionized water to which the natural zeolite has been added to produce a first mixture.

Preferably, in step (b), the first mixture may be heated for 90 to 100 hours.

Preferably, in step (a-1), the ratio of the natural zeolite to the deionized water may be 20 to 30 mL of deionized water per 4 g of the natural zeolite.

Preferably, in step (a-2), the cesium is added in the form of a cesium compound, and in step (a-2), 3 to 7 g of the cesium compound is added per 4 g of the natural zeolite added to the deionized water. can be

Preferably, the cesium may be cesium contained in any one of cesium carbonate (Cs ₂ CO ₃ ), cesium nitrate (CsNO ₃ ), or cesium chloride (CsCl).

Preferably, in step (a-2), 0.5 to 6 g of the sodium hydroxide may be added per 4 g of the natural zeolite added to the deionized water.

Preferably, in the step (a-2), 1 to 5 g of the sodium hydroxide may be added per 4 g of the natural zeolite added to the deionized water.

Preferably, (c) after step (b), the first mixture is washed with deionized water; And (d) after the step (c), the step of drying the first mixture may be further included.

In order to solve the problems of the prior art, the folucite according to the present invention can be prepared by the above-described folucite synthesis method.

In order to solve the problems of the prior art, the cesium immobilization method according to the present invention may include the step of immobilizing cesium by the above-described polucite synthesis method.

In order to solve the problems of the prior art, the method for disposing of cesium according to the present invention may include the step of immobilizing cesium by the above-described method for synthesizing folucite.

In the prior art, the hydrothermal synthesis reaction of folucite, which was carried out at around 150 to 200 ° C using an iron vessel, was carried out in a general Teflon chemical resistant vessel at 90 to 100 ° C and atmospheric pressure to synthesize folucite in the same way. , the working efficiency is increased, and the amount of waste liquid that can be treated at one time can be greatly increased.

1 is a diagram schematically illustrating a method for synthesizing folucite according to the present invention.
2 is a view showing XRD patterns of folusite prepared according to the prior art and folusite according to the present invention.

Hereinafter, preferred embodiments of the method according to the present invention will be described with reference to the accompanying drawings. In this process, the thickness of the lines shown in the drawings, the size of components, etc. may be exaggerated for clarity and convenience of explanation. In addition, the terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to the intention or custom of a user or operator. Therefore, definitions of these terms should be made based on the content throughout this specification.

1. Polucite Synthesis Method

A method for synthesizing folucite as a method for immobilizing radioactive cesium according to the present invention will be described with reference to FIG. 1 .

The radioactive cesium according to the present invention can be immobilized as it is synthesized into pollucite represented by the following Chemical Formula 1;

[Formula 1]

Cs _(1-x) Na _(x) AlSi ₂ O ₆ , where 0<x<0.5.

Natural zeolite is introduced into a vessel containing deionized water.

Such a container may be an ordinary Teflon container. The ratio of natural zeolite to deionized water may be 20 to 30 mL per 4 g of natural zeolite.

Thereafter, cesium and sodium hydroxide (NaOH) are added to the deionized water to which the natural zeolite is added, and the cesium is added in the form of a cesium compound.

The ratio of the natural zeolite and the cesium compound added to the deionized water may be 3 to 7 g of a cesium compound per 4 g of the natural zeolite, wherein the cesium compound is cesium carbonate (Cs ₂ CO ₃ ), cesium nitrate (CsNO ₃ ), or cesium chloride. (CsCl) may be any one.

The ratio of natural zeolite to sodium hydroxide added to deionized water may be 0.5 to 6 g of sodium hydroxide per 4 g of natural zeolite. Preferably, it may be 1 to 5 g of sodium hydroxide per 4 g of natural zeolite.

Thereafter, natural zeolite, cesium, and sodium hydroxide are added to a container containing deionized water, and the resulting first mixture may be heated at 90 to 100° C. for 90 to 100 hours under atmospheric pressure conditions. Preferably, it may be heated at 95 to 97° C. for 95 to 97 hours under atmospheric pressure conditions.

At this time, since the synthetic hot water temperature may be 100° C. or less under atmospheric pressure conditions, so that boiling of hot water can be prevented, the folucite synthesis process can be carried out only with a container that covers the lid without the need to use a pressurized iron container.

Thereafter, the first mixture is washed with deionized water and then dried to complete folucite synthesis.

Looking at the process of synthesizing folucite, the main reaction for synthesizing folucite in the above-described synthesis process is a solid phase transition that occurs during the dissolution of silicon (Si).

The natural zeolite used as a precursor was mainly composed of clinoptilolite and mordenite, so the silicon (Si)/aluminum (Al) ratio was 4 to 4.5, whereas the final product, polucite, was The ratio of silicon (Si)/aluminum (Al) is about 2 to 2.5. This is because silicon (Si) is melted from the natural zeolite by the OH group in the added sodium hydroxide (NaOH), and at the same time, the natural zeolite showing high cesium (Cs) adsorption efficiency compared to sodium (Na) is combined with cesium in the process of forming a new mineral. It is confirmed that folucite, an aluminosilicate mineral containing cesium, is formed during the preferential reaction.

2. Folucite Synthesis Results

4 g of natural zeolite was added to 25 mL of deionized water contained in a Teflon container. Thereafter, 5 g of cesium carbonate (Cs ₂ CO ₃ ) was added to the container, and the amount of sodium hydroxide added to the container was varied (0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0). , 5.5, 6.0 g) synthesis experiments were performed.

Thereafter, the lid of the Teflon container was closed and heated in an oven at 96° C. under atmospheric pressure for 96 hours. Since the synthetic hot water temperature was 96° C., there was no problem of boiling of hot water even when the lid was simply covered.

The product was then washed with deionized water and dried at 60°C.

Table 1 shows the synthesis results made by varying the input amount of sodium hydroxide.

[Table 1]

Looking at the results of the synthesis, it appears that a completely different material other than folucite was produced when sodium hydroxide was not added at all. When sodium hydroxide was added in 0.5 g, 5.5 g, and 6.0 g, folucite and other by-products were generated.

As described above, since folucite contains cesium in the aluminosilicate structure in a mineralized state, the amount of leaching is very low. known to be suitable.

However, when radioactive cesium is synthesized as other by-products, it is not suitable for immobilization of radioactive cesium, and even if it is eventually synthesized as other by-products, there is a high possibility that radioactive cesium is leached from other by-products. Therefore, as a result of the synthesis, a synthetic process in which only folucite is produced without generating other by-products will be considered as the most suitable for immobilizing radioactive cesium.

As a result, it can be seen that the most suitable immobilization of radioactive cesium can be achieved when sodium hydroxide is added within the range of 1.0 to 5.0 g during the synthesis process shown in Table 1 above.

Table 2 shows the chemical composition distribution of folucite according to the synthesis results.

[Table 2]

The chemical composition distribution of folucite shown in Table 2 is a chemical composition distribution corresponding to folucite synthesized according to the prior art as well as to folucite synthesized according to the method for synthesizing folucite according to the present invention.

That is, looking at the chemical composition distribution range of folucite synthesized by the method for synthesizing folucite according to the present invention, it is consistent with the chemical composition distribution range of folucite synthesized according to the prior art. Accordingly, it can be seen that folucite having the same chemical composition distribution range can be produced even when heated at 100° C. or less.

In FIG. 2, (b) is an XRD pattern of folucite produced according to the prior art, and (a) is an XRD pattern of folucite produced according to the present invention. As shown in the same pattern, it can be confirmed that folucite most suitable for immobilizing radioactive cesium is produced even when natural zeolite, cesium and sodium hydroxide are mixed with deionized water and then heated at 100° C. or less.

In the above, the present specification has been described with reference to the embodiments shown in the drawings so that those skilled in the art can easily understand and reproduce the present invention, but these are merely exemplary, and those skilled in the art may make various modifications and equivalent other modifications from the embodiments of the present invention. It will be appreciated that embodiments are possible. Therefore, the protection scope of the present invention should be defined by the claims.

Claims (16)

A method for synthesizing folucite as a method for immobilizing radioactive cesium,
(a-1) adding natural zeolite to deionized water;
(a-2) after step (a-1), the cesium and sodium hydroxide are added to the deionized water to which the natural zeolite has been added to produce a first mixture; and
(b) a method for synthesizing folucite comprising the step of heating the first mixture at 100° C. or less.
delete The method of claim 1,
A method for synthesizing folucite in which the first mixture is heated at 90 to 100° C. in step (b).
4. The method of claim 3,
In the step (b), the first mixture is heated at 95 to 97 ℃ folucite synthesis method.
4. The method of claim 3,
In the step (b), the method for synthesizing folucite comprising the step of heating the first mixture under atmospheric pressure conditions.
delete The method of claim 1,
A method for synthesizing folucite in which the first mixture is heated for 90 to 100 hours in step (b).
The method of claim 1,
In the step (a-1), the ratio of the natural zeolite to the deionized water is 20 to 30 mL of deionized water per 4 g of the natural zeolite.
The method of claim 1,
In step (a-2), the cesium is input in the form of a cesium compound,
In the step (a-2), 3 to 7 g of the cesium compound is added per 4 g of the natural zeolite added to the deionized water.
10. The method of claim 9,
The cesium is cesium carbonate (Cs ₂ CO ₃ ), cesium nitrate (CsNO ₃ ), or cesium chloride (CsCl) in any one of the cesium polucite synthesis method.
The method of claim 1,
In the step (a-2), 0.5 to 6 g of the sodium hydroxide per 4 g of the natural zeolite added to the deionized water is added to the folucite synthesis method.
12. The method of claim 11,
In the step (a-2), 1 to 5 g of the sodium hydroxide per 4 g of the natural zeolite added to the deionized water is added to the folucite synthesis method.
The method of claim 1,
(c) washing the first mixture with deionized water after step (b); and
(d) after step (c), further comprising the step of drying the first mixture.
[Claim 14] Folucite prepared by the method for synthesizing folucite according to any one of claims 1, 3 to 5, and 7 to 13.
A cesium immobilization method comprising the step of immobilizing cesium by the method for synthesizing folucite according to any one of claims 1, 3 to 5, and 7 to 13.
A method for disposing of cesium comprising the step of immobilizing cesium by the method for synthesizing folucite according to any one of claims 1, 3, 5, and 7 to 13.

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