WO2020045966A1 - Extraction method and extraction apparatus for cesium or strontium, using ternary phase separation - Google Patents

Abstract

The present invention relates to: a method for extracting cesium or strontium by using ternary phase separation; and an extraction apparatus to be used therefor. The present invention selectively separates cesium or strontium, extracts cesium or strontium as solid so as to minimize the volume of radioactive waste, uses an inexpensive organic solvent and recycles an organic solvent and an extractant, which remain after extraction, thereby exhibiting excellent economic efficiency, and can also carry out a continuous extraction process, thereby enabling effective extraction and removal of cesium or strontium up to a target level.

Description

Cesium or Strontium Extraction Method and Apparatus by Three-Component Phase Separation

The present invention relates to a method for extracting cesium or strontium using three-component phase separation and an extraction apparatus used therein.

Radioactive waste means the object of disposal contaminated with radioactive material. As the use of nuclear power increases in various fields such as nuclear power generation and isotope use, a large amount of radioactive waste is generated.

For example, when nuclear power plants generate power using heat generated after nuclear fission in a nuclear reactor, spent fuel remains. Used nuclear fuel is a representative high-level radioactive waste. In addition, when radioactive materials are accidentally released due to unexpected reasons, such as the Chernobyl nuclear power plant accident or the Fukushima Daiichi Nuclear Power Plant accident in Japan, radioactive waste is generated in large quantities due to the released radioactive materials.

In addition, the Republic of Korea is currently preparing for the dismantling of nuclear power plants. The dismantling of nuclear power plants is accompanied by a 'decontamination' process that removes or minimizes the radioactive substances present inside and outside the nuclear power plants. In this decontamination process, a large amount of radioactive waste is generated.

On the other hand, radioactive waste emits high-energy radiation, which can damage or alter human tissue, leading to brain tumors, ovarian cancer, testicular cancer, etc., and affecting human germ cells, causing genetic modifications. It is well known that increases the risk of birth defects.

Among these dangerous radioactive wastes, cesium (Cs) and strontium (Sr), the nuclear fission products that are most problematic in nuclear dismantling or nuclear accidents, are more dangerous due to their long half-life and high water-soluble properties. There is an urgent need to develop a technique for separating and strontium.

Selectivity is important in the development of techniques to separate cesium and strontium. Since cesium and strontium usually exist with metal salts with similar properties to them, a technique is needed to selectively separate cesium and strontium from them. For example, in the event of a nuclear accident, coolant waste contaminated with radionuclides, including cesium and strontium, may also enter the seawater. Similarly, salts of sodium (NaCl, NaNO _3, etc.), which are monovalent metals, are present at concentrations of thousands to tens of thousands times higher than those of cesium or strontium ions.

As a conventional method of selectively removing cesium and / or strontium, an adsorption method using an inorganic ion exchanger or a selective ion exchange resin is known.

However, these adsorption methods require extensive equipment such as circulation pumps, septic tanks, and filling tanks containing adsorbents, and require enormous energy to operate them. As in the case of an accident at Fukushima Daiichi Nuclear Power Plant in Japan, when the power is cut off, these facilities cannot be operated. Therefore, the risk of contamination by radioactive cesium and strontium is increased when the above treatment method is used.

In addition, adsorption methods generally have an exponentially lower amount of adsorption per unit mass of adsorbent when cesium or strontium is present at low concentrations due to chemical equilibrium limitations. However, cesium has a decay count value of 3600 Bq / g at a concentration of 1 ppb, which is very dangerous because it corresponds to low and medium radioactive waste. Since radioactive elements can be sufficiently dangerous even at low concentrations (1 ppb or less), a technique for effectively removing low concentrations of cesium or strontium is required.

In addition, when cesium or strontium is removed by the adsorption method, at low concentrations, the amount of adsorption per unit mass of the adsorbent is exponentially lowered, resulting in an excessive amount of waste adsorption radioactive waste. Since the disposal cost of radioactive waste is as high as 12190,000 won per 200 L drum (as of 2015), there is a problem that the adsorption method additionally incurs excessive disposal costs as well as removal costs.

Another method of selectively removing cesium and / or strontium is a liquid solvent extraction method using an ionic liquid (IL) as a solvent. However, the liquid liquid extraction method using the ionic liquid solvent has not yet been commercialized due to problems such as the cost of the ionic liquid.

As a solution to the problems of the prior art, the present inventors have developed a method of extracting cesium or strontium in a solid form using a small amount of ionic liquid (Korean Patent No. 10-1668956). The method using a small amount of ionic liquid has the advantage that cesium or strontium can be efficiently extracted even at low concentrations, and by extracting them in solid form, the volume of waste is reduced and no additional solidification operation is required.

However, in general, since the solvent extraction method requires a similar flow rate between the aqueous phase and the organic phase to effectively contact and continuously extract through liquid liquid separation, the method using only a small amount of ionic liquid is not suitable for the continuous extraction separation process. . For example, in the Fukushima accident, the amount of cesium or strontium waste required to be treated per day amounts to several hundred tons, whereas the amount of ionic liquid phase for solid-liquid extraction using this technique is only one thousandths of a ton, so it contains cesium or strontium. It is difficult to continuously treat large amounts of radioactive waste.

The inventors have separated the cesium or strontium selectively and studied to develop an economical method of continuous extraction of cesium or strontium while minimizing the amount of final radioactive waste.As a result, a large amount of cheap organic solvent was used to solidify cesium or strontium. The three-component phase separation treatment technology was developed by the common ion effect that can be continuously extracted in the form. By minimizing the generation of radioactive waste that is difficult to process, it is possible to continuously extract by using a large amount of cheap organic solvents instead of ionic liquids, and recycle the organic solvents and residual extractants used after extraction for economic efficiency. The present invention enables the efficient extraction of cesium or strontium.

One object of the present invention is to add a metal salt of a cesium or strontium cation with an ion exchangeable metal cation and an anion capable of combining with the cesium or strontium cation to form a hydrophobic complex to an aqueous solution containing cesium or strontium cation. A first step of preparing the receiving phase; A second step of preparing an organic phase including an extractant capable of forming a solid phase by combining with a hydrophobic complex containing cesium or strontium formed in the organic solvent from the first step; A third step of contacting the aqueous phase of the first step and the organic phase of the second step; And a fourth step of separating and recovering the reaction mixture of the third step into three phases of a solid phase, an aqueous phase, and an organic phase, respectively, to provide a method of extracting cesium or strontium.

Another object of the present invention is to provide a metal salt comprising an aqueous solution containing cesium or strontium cation, an ion exchangeable metal cation with cesium or strontium cation, and an anion capable of combining with the cesium or strontium cation to form a hydrophobic complex. An aqueous phase reservoir for storing an aqueous phase comprising; An organic phase storage tank storing an organic phase including an extractant capable of forming a solid phase by combining with a hydrophobic complex containing cesium or strontium formed in the aqueous phase in an organic solvent; A reaction tank in which the aqueous phase and the organic phase are in contact; A separation device associated with said reactor for separating an aqueous phase, an organic phase, and a solid phase; A treatment water reservoir connected to the separator for storing the receiving phase separated by the separator; And a first recovery tube connected to the organic phase storage tank from the reaction tank.

The present invention selectively separates cesium or strontium and extracts cesium or strontium as a solid to minimize the capacity of radioactive waste. In addition, the present invention requires a large amount of inexpensive organic solvent, requires only an amount of the extractant in an amount equivalent to cesium or strontium cation to minimize the amount of the extractant, and recycles the organic solvent and extractant remaining after extraction on a large scale. It enables the process and shows good economic efficiency. Moreover, the present invention has the effect of being able to efficiently extract and remove cesium or strontium to a desired level by a continuous extraction process.

1 is a diagram showing a result of cesium or strontium extracted in the solid phase by the cesium or strontium extraction method of the present invention.

2 is a diagram illustrating an exemplary cesium or strontium extraction process by the filtration separation method of the present invention.

3 is a diagram showing another exemplary cesium or strontium extraction process diagram of the present invention further comprising a second recovery tube.

4 is a diagram illustrating another exemplary cesium or strontium extraction process diagram of the present invention using a reactor as an organic phase reservoir.

Detailed description for carrying out the present invention is as follows. Meanwhile, each of the descriptions and the embodiments disclosed herein may be applied to each of the other descriptions and the embodiments. That is, all combinations of the various elements disclosed herein are within the scope of the present invention. In addition, the scope of the present invention is not limited by the specific description described below.

In addition, one of ordinary skill in the art can recognize or identify many equivalents to certain aspects of the invention described in this application using conventional experiments only. In addition, such equivalents are intended to be included in the present invention.

As one embodiment for achieving the above object, the present invention, a metal cation ion-exchangeable with cesium or strontium cation and a metal salt of an anion capable of combining with the cesium or strontium cation to form a hydrophobic complex, cesium or strontium A first step of preparing an aqueous phase by adding to an aqueous solution containing a cation;

A second step of preparing an organic phase including an extractant capable of forming a solid phase by combining with a hydrophobic complex containing cesium or strontium formed in the organic solvent from the first step;

A third step of contacting the aqueous phase of the first step and the organic phase of the second step; And

It provides a method of extracting cesium or strontium, comprising; a fourth step of separating and recovering the reaction mixture of the third step in three phases, respectively, solid phase, aqueous phase, and organic phase.

In this case, in the fourth step, the reaction mixture is allowed to settle so that the three phases are separated, and each of them is recovered independently, or the reaction mixture is filtered to separate the solid phase first from the liquid phase. It may be carried out by recovering each by separating the phases with an organic phase, but is not limited thereto.

The present invention is to solve the problem that the continuous extraction process is difficult due to the use of a small amount of expensive ionic liquid solvent when the cesium and / or strontium is removed by the liquid liquid extraction method by the ionic liquid solvent based on the conventional liquid-liquid extraction method It is designed for. Specifically, the present invention uses a metal cation that is ion-exchangeable with cesium and / or strontium cations and a metal salt of an anion capable of forming a hydrophobic complex with cesium and / or strontium cations by the ion exchange. Hydrophobic complexes containing cesium and / or strontium are formed in an aqueous solution, and the aqueous solution is brought into contact with an organic phase in which a small amount of a metal salt and a large amount of an organic solvent are mixed. Cesium or strontium is extracted through three-component separation of solid-liquid (aqueous phase) -liquid (organic phase) by solidifying cesium or strontium contained in an aqueous solution, including an extractant capable of forming a solid phase in combination with The organic phase recovered afterwards no longer contains radioactive material, so It is based on the finding that it can be reused in the extraction process without processing.

As used herein, the term "metal salt" is a substance consisting of a metal cation and a counter anion. The metal cations of the metal salts of the present invention are selected to allow ion exchange reactions in which the positions of the cations and cesium or strontium cations are exchanged. In addition, the counter anion of the metal salt of the present invention has a hydrophobic complex composed of a cesium or strontium cation formed according to this ion exchange reaction and an anion of the metal salt, so that the complex is in an organic phase when the aqueous phase containing the complex is in contact with an organic phase. Is selected to move to. In the present invention, the hydrophobic complex shifted to the organic phase combines with the extractant present in the organic phase to form a solid phase (precipitate), which makes it possible to extract cesium or strontium into the solid phase.

The metal salt may be an alkali metal salt or an alkaline earth metal salt, but is not particularly limited as long as it is present in an aqueous phase and may form an hydrophobic complex by ion exchange with a cesium or strontium cation. The anion of the metal salt is ^{_{Tf 2 N - (trifluoromethanesulfonylamide, (}} CF 3 SO 2) 2 N)), PF 6 - (hexafluorophosphate), BETI - (bis (perfluoroethylsulfonyl) imide), BF 4 -, AlCl 4 -, Al 2 _{^{Cl 7 -, AcO -, TfO}} - (trifluoromethanesulfonate), or _{CH 3 CH (OH) CO 2} - may be an (L-lactate), but is not limited thereto. In one experimental example of the present invention, using LiTf ₂ N or LiBETl as the metal salt, all of them showed excellent cesium removal efficiency (Experimental Examples 1 and 3).

The metal salt may be present in a mole number of 0.1 to 10 times the cesium or strontium cation. The amount of the metal salt may be specifically 0.1 to 7 times, more specifically 0.1 to 5 times and most specifically 0.1 to 3 times the cesium or strontium cation, but is not limited thereto. For example, when the amount of the metal salt is less than 0.1 times the number of moles of cesium or strontium cations, the reaction rate is low, and the reaction takes a long time, and the amount extracted by a single run may be small, requiring several times of repeated performance.

As used herein, the term "extracting agent" is a substance which is dissolved in an organic solvent and is present in an organic phase, and may be combined with the hydrophobic complex to form a solid phase (precipitate). As the extractant, but not limited thereto, a crown ether-based extractant may be used. Specifically, DCH18C6 (Dicyclohexano-18-crown-6), DB21C7 (Dibenzo-21-crown-7), DB24C8 (Dibenzo-24 -crown-8), or a combination thereof can be used.

The extractant may be present at 0.1 to 10 times the number of moles of cesium or strontium cation. The amount of extractant may specifically be 1 to 9 times, more specifically 1 to 7 times and most specifically 1 to 5 times the number of moles of cesium or strontium cation, but is not limited thereto. When the amount of the extractant is less than 0.1 times the number of moles of cesium or strontium cation, the extraction efficiency of cesium and strontium may be lowered.

In the present invention, the organic solvent is not particularly limited as long as it can be separated from the aqueous phase and can dissolve the extractant. Non-limiting examples of organic solvents include saturated hydrocarbons such as octane, nonane, tecan, undecane, dodecane, tridecane and kerosene. Here, kerosene means a C _6-16 hydrocarbon mixture. In one experimental example of the present invention, when dodecane or kerosene were used, all three-phase separation of solid-liquid-liquid phase appeared, and it was confirmed that the cesium removal efficiency was excellent (Experimental Examples 1 and 2).

The amount of the organic solvent is not particularly limited as long as the three-phase separation of the organic phase, the aqueous phase, and the solid phase occurs, but 3 vol% to 150 vol%, specifically 5 vol% to 100 vol, based on the volume of the cesium or strontium aqueous solution. May be%. When the amount of the organic solvent is used in less than 3% by volume based on the volume of the cesium or strontium aqueous solution, it may be difficult to perform a continuous separation process due to the difference in the flow rate of the organic phase and the aqueous phase. In the experimental example of the present invention it was confirmed that the three-phase separation phenomenon when the organic solvent is used in the volume ratio (Experimental Examples 1 to 3).

Alternatively, the organic solvent may be used in an amount of 0.1 to 100 times the number of moles based on the number of moles of the extractant included therein, but is not limited thereto. In a specific embodiment of the present invention, it was confirmed that the cesium removal efficiency of more than 90% in a wide volume range of 1 to 20 mL containing the same amount of extractant regardless of the type of organic solvent.

When the aqueous phase containing cesium or strontium cation together with the metal salt is brought into contact with the organic phase containing the extractant in the organic solvent, the hydrophobic complex formed in the aqueous phase moves to the organic phase, and the hydrophobic complex transferred to the organic phase is in the organic phase. Combine with extractant to form a precipitate (solid phase).

In the present invention, the contacting of the aqueous phase and the organic phase is not particularly limited, but may be performed by a counter current solvent extraction method, a parallel current solvent extraction method, or a mixed contact method. For example, the aqueous phase and the organic phase may be simply mixed to allow the aqueous phase and the organic phase to contact and react at the interface thereof, or the aqueous phase and the organic phase may be agitated in the reactor to improve the contact. When the aqueous phase and the organic phase are brought into contact with each other by stirring, a mixture of the aqueous phase and the organic phase may be left after the reaction to perform phase separation.

The method of extracting cesium or strontium of the present invention measures the concentration of cesium or strontium in the aqueous phase recovered from the fourth step, and when the measured concentration is above a predetermined level, the aqueous phase is returned to the first step, and the predetermined level is determined. If less than that may further comprise the step of moving the receiving phase to the treated water reservoir. The returned aqueous phase may be replenished with the metal salt if necessary.

In addition, the method of extracting cesium or strontium of the present invention further includes the step of returning the organic phase recovered from the fourth step to the second step to reuse the recovered organic phase as an organic solvent to perform the third to fifth steps. Can be done repeatedly. At this time, the extracted organic phase may be supplemented with the extractant if necessary. In one experimental example of the present invention, it was confirmed that the cesium or strontium was continuously extracted as well as maintaining excellent cesium removal efficiency even when the organic phase was reused and extracted twice (Experimental Example 4). Through the reuse of the remaining extractant and organic solvent and the sequencing of the extraction process, the extraction method of the present invention is expected to achieve excellent economic efficiency.

In addition, the aqueous solution containing the cesium or strontium cation of the present invention may be derived from radioactive waste, the cesium or strontium cation of the present invention is non-radioactive cesium or strontium cation; Radioactive cesium or strontium cations; Or combinations thereof.

The method of extracting cesium or strontium of the present invention may increase the extraction efficiency of cesium or strontium by adjusting the concentration of total cesium or strontium cations including radioactive cesium or strontium cations and non-radioactive cesium or strontium cations. For example, the extraction method may include adjusting the concentration of cesium or strontium cations by additionally adding cesium or strontium when the total concentration of cesium or strontium cations is low. In this case, since the concentration of cesium or strontium cations is high, the extraction efficiency of cesium or strontium may be increased depending on chemical equilibrium. At this time, the concentration of the total cesium or strontium cation may be adjusted to 0.1 to 100 ppm, but is not limited thereto.

The extraction method of the present invention selectively separates cesium or strontium, and extracts cesium or strontium as a solid to minimize the capacity of radioactive waste, as well as using a cheap organic solvent, by recycling the organic solvent and extractant It shows good economic efficiency and can efficiently extract cesium or strontium to the desired level.

In another embodiment, the present invention provides a metal salt comprising an aqueous solution containing cesium or strontium cations, an ion exchangeable metal cation with cesium or strontium cations, and an anion capable of combining with the cesium or strontium cations to form a hydrophobic complex. An aqueous phase storage tank for storing the aqueous phase comprising a;

An organic phase storage tank storing an organic phase including an extractant capable of forming a solid phase by combining with a hydrophobic complex containing cesium or strontium formed in the aqueous phase in an organic solvent;

A reaction tank in which the aqueous phase and the organic phase are in contact;

A separation device associated with said reactor for separating an aqueous phase, an organic phase, and a solid phase;

A treatment water reservoir connected to the separator for storing the receiving phase separated by the separator; And

It provides a cesium or strontium extraction apparatus comprising a; a first recovery pipe connected to the organic phase storage tank from the reaction tank. An example of such an extraction apparatus is shown in FIG.

For example, in the extracting apparatus of the present invention, the apparatus for separating the solid phase and the liquid phase, such as filtration, can be reused, and the apparatus for discharging the separated solid phase, i.e., the precipitate, immediately or in a separate reservoir to be discharged when a predetermined amount or more is added. It may be provided as, but is not limited thereto.

The cesium or strontium extraction device, measuring device provided in the separation device or the treated water storage tank to determine the concentration of cesium or strontium in the aqueous phase separated by the separation device; And a second recovery pipe connected to the receiving bed reservoir from the separator or the treated water reservoir connected to the measuring device. An example of the extraction apparatus further including a second recovery tube is shown in FIG. 3. The second recovery pipe may be connected to the separation device.

The cesium or strontium extraction device of the present invention, when the concentration of cesium or strontium in the separated aqueous phase calculated by the measuring device is less than a predetermined level, the separated aqueous phase is accommodated in the treated water reservoir, the concentration of cesium or strontium If more than a predetermined level may be to return the separated receiving bed to the receiving bed storage tank through the second collection pipe.

The aqueous phase reservoir of the present invention stores an aqueous phase comprising cesium or strontium cations and the metal salt of the present invention, and the organic phase reservoir of the present invention stores an organic phase comprising the organic solvent and extractant of the present invention.

The reaction tank of the present invention receives an aqueous phase and an organic phase from the aqueous phase storage tank and the organic phase storage tank to contact the aqueous phase and the organic phase. In the reaction tank, a reaction occurs in which the hydrophobic complex of the present invention formed in the aqueous phase moves to the organic phase and forms a solid phase by combining with an extractant in the organic phase. In the reactor, the aqueous phase and the organic phase may exist in a separated state by the difference in density, and may be present in a mixed state by a stirring device which may be further provided.

In the cesium or strontium extraction device of the present invention, the reaction tank itself may be used as the reaction tank and the organic phase storage tank of the separated organic phase, and thus the organic phase storage tank and the first recovery pipe may be omitted. Specifically, in the cesium or strontium extraction device, the organic phase is maintained in the reaction tank, the organic solvent and the extractant added to the organic phase are added directly to the reaction tank, and only the aqueous phase is the aqueous phase reservoir-reactor-separator-aqueous phase reservoir or aqueous phase. The tank may be refluxed through a reservoir, a reactor, a separator, a treatment water reservoir, a second recovery pipe, and a water phase reservoir. Thus, the example of the extraction apparatus using the reaction tank itself as an organic phase storage tank is shown in FIG.

The separator of the present invention is connected to the lower end of the reactor, and serves to separate the organic phase, the aqueous phase, and the solid phase, respectively. The separation device may be a filtration device, an extraction device, a centrifugal device, or a combination thereof, but is not particularly limited as long as it can separate the organic phase, the aqueous phase, and the solid phase, respectively. When the measuring device is provided in the separator, the separator moves the separated aqueous phase to the treated water reservoir when the concentration of cesium or strontium is reduced below a predetermined level, and separates when the concentration of cesium or strontium is above a predetermined level. The received receiving phase may be to repatriate the receiving vessel through the second collection pipe.

The treated water storage tank of the present invention stores an aqueous phase (also called treated water) separated by a separating device. When the measuring device is provided in the treated water reservoir, the treated water reservoir receives a separate aqueous phase when the concentration of cesium or strontium is reduced below a predetermined level, and separate receiving when the concentration of cesium or strontium is higher than a predetermined level. The phase may be to be returned to the receiving reservoir through the second collection pipe.

In addition, the organic phase separated by the separator may be returned to the reactor through the first recovery pipe, when the extractant may be supplemented with the organic phase if necessary.

Extraction apparatus of the present invention may be a batch, continuous, or a combination thereof.

Such an extraction apparatus of the present invention not only can efficiently extract cesium or strontium to a desired level, but also has an advantageous effect of recycling organic solvents and extractants to achieve excellent economic efficiency.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, these examples are intended to illustrate the present invention in more detail, and the scope of the present invention is not limited by these examples.

Example 1 Extraction Method of Cesium or Strontium

An organic solvent was prepared by adding 2 mmol of DCH18C8 as an extractant to dodecane, an organic solvent. An aqueous phase was prepared by adding 2 mmol of CsNO ₃ or Sr (NO ₃ ) ₂ and 5 mmol of LiTf ₂ N as a metal salt to 20 mL of water. The organic and aqueous phases were contacted to react. As shown in FIG. 1, a white solid phase was formed by the reaction, and a three-phase separation phenomenon of an organic phase, a water-soluble phase, and a solid phase appeared over time.

Experimental Example 1: Extraction efficiency and phase separation of cesium according to the volume of the organic solvent

The present inventors attempted to confirm the results of phase separation and the extraction efficiency of cesium according to the volume of the organic solvent used.

To this end, cesium extraction was performed in the same manner as in Example 1, but the organic phase was prepared by adjusting the volume of dodecane, an organic solvent, to 1 mL, 5 mL, 10 mL, or 20 mL, respectively. For each, the removal efficiency and phase separation form of cesium were confirmed, and the results are shown in Table 1 below. Phase separation was represented by solid phase (S)-liquid phase (L), solid phase (S)-liquid phase (L)-liquid phase (L), or liquid phase (L)-liquid phase (L).

Dodecane Volume (mL)	Cs removal efficiency (%)	Phase Separation (S-L / S-L-L / L-L)
One	97.82	S-L-L
5	97.68	S-L-L
10	97.60	S-L-L
20	97.31	S-L-L

As shown in Table 1, when the volume of the organic solvent to the volume of the cesium aqueous solution (20 mL) is a ratio of 1: 1 to 1:20, all samples are solid (S)-regardless of the ratio of the organic phase and the aqueous phase. Phase separation of the liquid phase (L) -liquid phase (L) was shown, and the cesium removal efficiency was found to be excellent cesium removal efficiency of 90% or more.

Experimental Example 2: Extraction Efficiency and Phase Separation of Cesium According to Organic Solvents

The present inventors intended to confirm the extraction efficiency of cesium and the result of phase separation according to the type of organic phase.

To this end, cesium extraction was performed in the same manner as in Experimental Example 1, except that kerosene was used instead of dodecane as an organic solvent, and the results are shown in Table 2 below.

Kerosene Volume (mL)	Cs removal efficiency (%)	Phase Separation (S-L / S-L-L / L-L)
One	98.23	S-L-L
5	97.66	S-L-L
10	97.27	S-L-L
20	96.58	S-L-L

As shown in Table 2, when the volume of the organic solvent to the volume of the cesium aqueous solution (20 mL) is a ratio of 1: 1 to 1:20, all the samples using kerosene as the organic solvent were dodecane as the organic solvent. Similar to the case of use, the solid phase (S) -liquid phase (L) -liquid phase (L) showed a phase separation phenomenon, cesium removal efficiency was found to be excellent cesium removal efficiency of 90% or more. In addition, it was confirmed that all samples using kerosene showed similar cesium removal efficiency as the samples using the same volume of dodecane.

Experimental Example 3: Extraction efficiency and phase separation of cesium according to the anion type of the metal salt

The present inventors attempted to confirm the extraction efficiency and phase separation of cesium according to the anion type of the metal salt.

To this end, cesium extraction was performed in the same manner as in Experimental Example 1, except that LiBETl was used instead of LiTf ₂ N as the metal salt, and the results are shown in Table 3 below.

Dodecane Volume (mL)	Cs removal efficiency (%)	Phase Separation (S-L / S-L-L / L-L)
One	93.97	S-L-L
5	93.96	S-L-L
10	94.34	S-L-L
20	94.56	S-L-L

As shown in Table 3, when the volume of the organic solvent to the volume of the cesium aqueous solution (20 mL) is a ratio of 1: 1 to 1:20, all samples using LiBETl as the metal salt used LiTf ₂ N as the metal salt. Similar to the case, the solid phase (S) -liquid phase (L) -liquid phase (L) showed a phase separation phenomenon, cesium removal efficiency was found to be excellent cesium removal efficiency of 90% or more.

Experimental Example 4: Extraction Efficiency of Cesium in Reuse of Organic Phase

The present inventors tried to confirm the extraction efficiency of cesium when reusing the organic phase.

To this end, it was carried out in the same manner as in Example 1, but the cesium was first extracted by adding 6 mmol of the extractant so that the concentration of the extractant is three times the concentration of cesium in the aqueous phase, the new cesium simulated waste solution was first The organic phase used in the extraction was reused for secondary extraction. The results are shown in Table 4 below.

Extraction count	Cs removal efficiency (%)
1 time	97.49
Episode 2	93.28

As shown in Table 4, it was confirmed that the cesium removal efficiency of more than 90% is maintained even when the organic phase is reused twice. Through this, it was confirmed that cesium or strontium cations can be economically extracted by recycling the organic solvent and the extractant remaining after extraction, and it is also possible to continuously extract and remove cesium or strontium cations to a target concentration. I could confirm it.

Overall, it was confirmed that cesium and / or strontium can be removed with a high efficiency of 90% or more regardless of the type and / or the amount of the organic solvent, the type of the metal salt, and the reuse of the organic solvent.

From the above description, those skilled in the art will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. In this regard, the embodiments described above are to be understood in all respects as illustrative and not restrictive. The scope of the present invention should be construed that all changes or modifications derived from the meaning and scope of the following claims and equivalent concepts rather than the detailed description are included in the scope of the present invention.

Claims (18)

1. A first method of preparing a water-soluble phase by adding a metal salt of a cesium or strontium cation and an ion exchangeable metal cation and an anion capable of combining with the cesium or strontium cation to form a hydrophobic complex to an aqueous solution containing cesium or strontium cation. step;

   A second step of preparing an organic phase including an extractant capable of forming a solid phase by combining with a hydrophobic complex containing cesium or strontium formed in the organic solvent from the first step;

   A third step of contacting the aqueous phase of the first step and the organic phase of the second step; And

   And a fourth step of separating and recovering the reaction mixture of the third step into three phases of a solid phase, an aqueous phase, and an organic phase, respectively.
2. The method of claim 1, wherein the concentration of cesium or strontium in the aqueous phase recovered from the fourth step is measured, and if the measured concentration is greater than or equal to a predetermined level, the aqueous phase is returned to the first phase, and if less than the predetermined level, The method of extracting cesium or strontium further comprising moving the phase to a treated water reservoir.
3. The method of claim 1, further comprising the step of returning the organic phase recovered from the fourth step to the second step by repeating steps 3 to 5 by reusing the recovered organic phase as an organic solvent. That is, cesium or strontium extraction method.
4. The method of extracting cesium or strontium according to claim 1, wherein the metal salt is an alkali metal salt or an alkaline earth metal salt.
5. The method of claim 1, wherein the anion of said metal salt is ^{_{Tf 2 N - (trifluoromethanesulfonylamide, (}} CF 3 SO 2) 2 N)), PF 6 - (hexafluorophosphate), BETI - (bis (perfluoroethylsulfonyl) imide), BF 4 -, _{^{AlCl 4 -, Al 2 Cl 7}} -, AcO -, TfO - (trifluoromethanesulfonate), or _{CH 3 CH (OH) CO 2} - (L-lactate) would of, extraction of cesium or strontium.
6. The method of claim 1, wherein the extracting agent is at least one selected from the group consisting of DCH18C6 (Dicyclohexano-18-crown-6), DB21C7 (Dibenzo-21-crown-7), and DB24C8 (Dibenzo-24-crown-8) Will, cesium or strontium extraction method.
7. The method of extracting cesium or strontium according to claim 1, wherein the organic solvent is saturated hydrocarbon.
8. The method of claim 1, wherein the third step is performed by a counter current solvent extraction method, a parallel current solvent extraction method, or a mixed contact method.
9. The method of extracting cesium or strontium according to claim 1, wherein the metal salt is 0.1 to 10 times the number of moles of cesium or strontium cation.
10. The method of extracting cesium or strontium according to claim 1, wherein the extractant is 0.1 to 10 times the number of moles of cesium or strontium cation.
11. The method of extracting cesium or strontium according to claim 1, wherein the aqueous solution containing cesium or strontium cations is derived from radioactive waste.
12. An aqueous phase storing an aqueous phase containing a cesium or strontium cation and a metal salt of a metal salt of an anion that is ion-exchangeable with the cesium or strontium cation and an anion capable of combining with the cesium or strontium cation to form a hydrophobic complex Reservoir;

    An organic phase storage tank storing an organic phase including an extractant capable of forming a solid phase by combining with a hydrophobic complex containing cesium or strontium formed in the aqueous phase in an organic solvent;

    A reaction tank in which the aqueous phase and the organic phase are in contact;

    A separation device associated with said reactor for separating an aqueous phase, an organic phase, and a solid phase;

    A treatment water reservoir connected to the separator for storing the receiving phase separated by the separator; And

    Cesium or strontium extraction apparatus comprising a; a first recovery pipe connected to the organic phase storage tank from the reaction tank.
13. 13. The apparatus according to claim 12, further comprising: a measuring device provided in the separating device or the treated water reservoir to check the cesium or strontium concentration in the aqueous phase separated by the separating device; And

    And a second recovery pipe connected to the receiving bed reservoir from the separator or the treated water reservoir connected to the measuring device.
14. The apparatus for extracting cesium or strontium according to claim 12, wherein the reaction tank itself is used as a separate organic phase reaction tank and an organic phase storage tank, and thus the organic phase storage tank and the first recovery tube are omitted.
15. The method according to claim 13, wherein when the concentration of cesium or strontium in the separated aqueous phase calculated by the measuring device is less than the predetermined level, the separated aqueous phase is accommodated in the treated water reservoir, and the concentration of cesium or strontium is greater than or equal to the predetermined level. If the separated aqueous phase is to be returned to the aqueous phase reservoir via a second recovery tube, cesium or strontium extraction device.
16. The cesium or strontium extraction device of claim 12, wherein the separation device is a filtration device, an extraction device, a centrifuge device, or a combination thereof.
17. The cesium or strontium extraction device of claim 12, wherein the reactor further comprises a stirring device.
18. 13. The cesium or strontium extraction device of claim 12, wherein the batch is continuous, continuous, or a combination thereof.

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