KR101835132B1 - Inorganic synthesis composite and method for separation and solidification of chlorinated impurities in waste electrolyte - Google Patents

Abstract

The present invention relates to an inorganic synthetic medium containing a composite oxide containing silicon (Si), aluminum (Al), lithium (Li) and boron (B), and a method of separating and solidifying chloride based impurities in the electrolytic process .

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method for separating and solidifying a chloride-based impurity in an electrolytic process using an inorganic synthetic medium and an electrolytic process using the inorganic synthetic medium,

The present invention relates to an inorganic synthetic medium and a method for separating and solidifying chloride-based impurities in the waste electrolytes generated in an electrolytic process using the inorganic synthetic medium.

In an electrolytic process in which a specific metal is refined and separated and recovered in a high-purity form in a high-temperature electrolyte (molten salt) using an electrochemical method, an impurity-containing waste electrolyte is generated. Particularly, in the pyro processing for spent nuclear fuel, a considerable amount of chloride-based impurities is generated as an impurity in the waste electrolyte, and at this time, the chloride-based impurity may include a radionuclide.

For the reduction of the waste electrolytes and the stable treatment of the impurities, it is most effective to selectively separate the chloride-based impurities in the waste electrolytes, solidify them into a stable form, and purify the waste electrolytes in a form reusable. To this end, it is converted to a thermally and chemically stable form through the selective reaction of chloride-based impurities and additive in the present electrolytic solution, and only the electrolyte is volatilized and condensed by distillation under reduced pressure to separate chloride-based impurities from the waste electrolytes. Are mixed with each other to prepare a stable solid form. However, in order to carry out such a process technology, it is difficult to handle a large amount of electrolyte because the electrolyte must be taken out from the electrolytic process reactor. In order to react with chlorine-based impurities in the waste electrolyte and to produce solid- Each additive must be injected. In particular, after the additive is added to the solidified material, the solidified material is produced through the heat treatment after the mixing process, which complicates the process.

Since the amount of electrolyte to be treated in this way is large, the number of times the additive is injected and the complexity of the process can greatly affect the economical efficiency of the process technology, and therefore, a method capable of improving the process technology and improving the economy is introduced It is necessary.

Korean Patent Laid-Open Publication No. 10-2015-0107188 (Feb.

The present invention relates to an inorganic synthetic medium containing silicon (Si), aluminum (Al), lithium (Li) and boron (B) containing complex oxides and separating and solidifying chloride- And to provide a method for separating and solidifying chloride-based impurities in the waste electrolytes generated in an electrolytic process using the same.

However, the technical problem to be solved by the present invention is not limited to the above-mentioned problems, and other matters not mentioned can be clearly understood by those skilled in the art from the following description.

The present invention relates to an inorganic synthetic medium containing a composite oxide containing silicon (Si), aluminum (Al), lithium (Li) and boron (B) and capable of separating and solidifying chloride- to provide.

(A) an inorganic synthetic medium containing silicon (Si), aluminum (Al), lithium (Li) and boron (B) -containing complex oxides is charged into the waste electrolytes generated in the electrolytic apparatus step; (b) separating the inorganic synthetic medium trapping the chloride-based impurities from the spent electrolyte after the inorganic synthetic medium is reacted with the chloride-based impurities contained in the waste electrolytic solution to purify the waste electrolytic solution; And (c) separating the residual salt contained in the inorganic synthetic medium trapped by the separated chloride-based impurities and then heat-treating the separated salt, thereby separating and solidifying the chloride-based impurities in the waste electrolytic solution. to provide.

According to the present invention, an inorganic synthetic medium containing a composite oxide containing silicon (Si), aluminum (Al), lithium (Li) and boron (B) The electrolyte can be immediately reused without taking out the electrolyte, and the amount of waste due to the electrolyte can be minimized.

In addition, the separated chloride-based impurities can be produced in a stable form (solid state form) by being heat-treated in a state of being trapped in an inorganic synthetic medium without additional pretreatment, that is, without addition of additives such as a solidification medium, And advantages in raw material aspect.

1 is a graph showing an XRD pattern analysis result of an inorganic synthetic medium prepared according to Example 1. Fig.
2 is a photograph showing the inorganic synthetic material in (a) an inorganic synthetic medium, (b) an inorganic synthetic medium in which NdCl ₃ is captured, and (c) a glass solidified form in Example 2.
3 is a graph showing an XRD pattern analysis result of a mixture of an inorganic synthetic medium in which NdCl ₃ is captured and a remaining inorganic synthetic medium in which NdCl ₃ is not captured in Example 2. FIG.
FIG. 4 is a graph showing the SEM analysis results of the inorganic synthetic medium separated in the form of a free solid in Example 2. FIG.

The inventors of the present invention have studied silicon (Si), aluminum (Al), lithium (Li), and the like in the course of studying a method for separating and solidifying chloride-based impurities contained in the waste electrolytes in the electrolytic process of spent nuclear fuel, ) And boron (B) -containing composite oxide, it is possible to easily separate and stabilize the radionuclide-containing chloride without withdrawing the electrolyte, thereby completing the present invention.

Hereinafter, the present invention will be described in detail.

Inorganic synthetic medium

The present invention relates to an inorganic synthetic medium containing a composite oxide containing silicon (Si), aluminum (Al), lithium (Li) and boron (B) and capable of separating and solidifying chloride- to provide.

The inorganic synthetic medium according to the present invention is used for separating and solidifying chloride-based impurities in the waste electrolytes generated in an electrolytic process, particularly an electrolytic process of a spent nuclear fuel, and includes silicon (Si), aluminum (Al) And boron (B) -containing complex oxide.

Specifically, the composite oxide includes 15 to 25 parts by weight of silicon (Si), 5 to 15 parts by weight of aluminum (Al), 10 to 20 parts by weight of lithium (Li) based on 100 parts by weight of the composite oxide, And 1 part by weight to 10 parts by weight of boron (B).

More specifically, the composite oxide may include silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), lithium oxide (Li ₂ O) and boron oxide (B ₂ O ₃ ) ₂ ) 39.5 to 45.0 wt% aluminum oxide (Al ₂ O ₃ ) 26.4 to 30.0 wt% lithium oxide (Li ₂ O) 10.4 to 21.0 wt% boron oxide (B ₂ O ₃ ) 13.1 To 14.9% by weight, but is not limited thereto. At this time, silicon oxide (SiO ₂ ) plays a role of glass solidification as a main component of the inorganic synthetic medium and aluminum oxide (Al ₂ O ₃ ) plays a role for bonding between materials in the inorganic synthetic medium (Li ₂ O) plays a role in reducing the melting temperature for trapping chloride-based impurities and solidifying glass, and boron oxide (B ₂ O ₃ ) is a promoter of glass solidification (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), lithium oxide (Li ₂ O) and boron oxide (B ₂ O ₃ ), which is used for the purpose of reducing the melting temperature for glass solidification. May be varied according to the kind of the chloride-based impurities, the reaction conditions of the inorganic synthetic medium and the chloride-based impurities, or the heat treatment conditions of the separated inorganic synthesis medium.

SiO ₂ Al ₂ O ₃ Li ₂ O B ₂ O ₃ Composition ratio (% by weight) 39.5 to 45.0 26.4 to 30.0 10.4 to 21.0 13.1 to 14.9

In this case, the composite oxide can be prepared by the tetraethyl ortho silicate (TEOS), aluminum chloride (AlCl3 · 6H2O), lithium hydroxide (LiOH) and boric acid (H ₃ BO ₃₎ as a starting material. For example, the complex oxide is prepared by dissolving boric acid (H ₃ BO ₃ ), aluminum chloride (AlCl ₃ .6H ₂ O) and lithium hydroxide (LiOH) in distilled water (DI-Water) at room temperature and mixing them, then adding tetraethylorthosilicate (TEOS) may be dissolved in ethanol at room temperature, reacted with each other, and the precipitate may be separated by filtration under reduced pressure. Thereafter, it is dried at 100 to 200 ° C for 1 to 5 hours to remove moisture, and then heat-treated at 500 to 800 ° C for 5 to 20 hours to remove ethanol, nitric acid, chlorine, etc., .

The inorganic synthesis medium may include Li ₂ Al ₂ Si ₃ O ₁₀ , and B ₂ O ₃ may be included in an amorphous form.

The chloride-based impurities may be contained in the spent electrolyte in the electrolytic process of the spent nuclear fuel. That is, when the spent fuel is used as a negative electrode material in the electrolytic process for refining and separating and recovering the spent fuel with high purity, the negative electrode material reacts with the chloride ion in the molten salt, Lt; / RTI > In order to reuse the spent electrolyte, these impurities need to be separated and prepared in a stable form, that is, a solid form, preferably a glass solid form.

The chloride-based impurities include, but are not limited to, one or more nuclide elements selected from the group consisting of alkaline earth metals, rare earth metals and transuranic elements (TRU). Specifically, the nuclide element includes an alkaline earth metal including strontium (Sr); At least one rare earth metal selected from the group consisting of yttria (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm) and europium (Eu); Or one or more ultra-uranium elements (TRU) selected from the group consisting of neptunium (Np), plutonium (Pu), americium (Am) and curium (Cm).

The inorganic synthetic medium may have a porous structure having a wide surface area so as to easily capture the chloride-based impurities, and is preferably 100 탆 or less, but is not limited thereto.

after use  Nuclear fuel In the electrolytic process  Occurring Waste electrolyte  of mine Chloride system  How to separate and solidify impurities

(A) charging an inorganic synthetic medium containing silicon (Si), aluminum (Al), lithium (Li) and boron (B) -containing complex oxides into a waste electrolyte generated in an electrolytic apparatus; (b) separating the inorganic synthetic medium trapping the chloride-based impurities from the spent electrolyte after the inorganic synthetic medium is reacted with the chloride-based impurities contained in the waste electrolytic solution to purify the waste electrolytic solution; And (c) separating the residual salt contained in the inorganic synthetic medium trapped by the separated chloride-based impurities and then heat-treating the separated salt, thereby separating and solidifying the chloride-based impurities in the waste electrolytic solution. to provide.

First, a method of separating and solidifying chloride-based impurities in the waste electrolytes generated in an electrolytic process according to the present invention is a method of separating and solidifying chloride-based impurities in a waste electrolytic solution according to the present invention by introducing silicon, aluminum (Al), lithium (Li) And boron (B) -containing composite oxide (step (a)).

The loading of the inorganic synthetic medium can be performed in a state that the inorganic synthetic medium is supported on a crucible, that is, a porous crucible having a porous crucible, in particular, a stirrer. More specifically, the inorganic synthetic medium is loaded on the porous crucible Into the interior of the waste electrolyte. At this time, the porous crucible may be mounted on a flange formed on the upper part of the reactor.

The specific contents of the inorganic synthetic medium are as described above.

The waste electrolyte is preferably heated to 450 ° C to 500 ° C, but it is not limited thereto and can be controlled depending on the type of the eutectic salt constituting the waste electrolyte. For example, when the waste electrolyte is less than 450 ° C., there is a problem in that the trapping reaction using the inorganic synthetic medium is not actively conducted, and when the waste electrolyte exceeds 500 ° C., the volatilization of the eutectic salt may be increased during the operation .

Specifically, the waste electrolyte preferably includes a eutectic salt selected from the group consisting of LiCl-KCl, LiF-KF and Li ₂ CO ₃ -K ₂ CO ₃ , but is not limited thereto. Since the eutectic salt contains chlorine ions as described above, when the spent fuel is used as a cathode material, the cathode material may react with chlorine ions in the eutectic salt to generate chloride-based impurities.

A method for separating and solidifying a chloride-based impurity in a pulsed electrolyte generated in an electrolytic process according to the present invention comprises reacting the inorganic synthesis medium with a chloride-based impurity contained in the pulsed electrolyte, And separating the inorganic synthetic medium to purify the spent electrolyte (step (b)).

First, the inorganic synthetic medium and the chloride-based impurities contained in the waste electrolyte may be reacted.

The reaction may be carried out by stirring at a speed of 100 rpm to 200 rpm.

After the reaction, the inorganic synthetic medium in which the chloride-based impurities are trapped is selected from the group consisting of a lithium-silicon (Si) oxide containing a nuclide element, an aluminum-silicon (Si) oxide containing a nuclide element, Silicon (Si) oxide or silicon (Si) oxide containing a nuclide element, wherein the nuclide element is an alkaline earth metal comprising strontium (Sr); At least one rare earth metal selected from the group consisting of yttria (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm) and europium (Eu); Or one or more ultra-uranium elements (TRU) selected from the group consisting of neptunium (Np), plutonium (Pu), americium (Am) and curium (Cm). In addition, it may contain B ₂ O ₃ in amorphous form.

For example, when the nuclide element contained in the chloride-based impurity is neodymium (Nd), the inorganic synthetic medium in which the chloride-based impurity is captured may include LiNdSiO ₄ or the like.

Next, the inorganic synthetic medium in which the chloride-based impurities are trapped can be separated from the waste electrolytes to purify the waste electrolytes. At this time, the separation can be performed by taking out the porous crucible. Thereby, the waste electrolytes can be purified and immediately reused without taking out the electrolyte, which has an advantage that the amount of waste due to the electrolyte can be minimized.

The method for separating and solidifying the chloride-based impurities in the waste electrolytes generated in the electrolytic process according to the present invention comprises separating the residual salts contained in the inorganic synthetic medium in which the separated chloride-based impurities are trapped, ) Step].

First, the residual salt contained in the inorganic synthetic medium in which the separated chloride-based impurities are trapped can be separated. Specifically, after the porous crucible is taken out, a part of the residual salt remains in the porous crucible bearing the chloride-based impurity, and a part of the remaining salt remains at 50 to 900 ° C, preferably 700 to 900 ° C Volatilization and condensation.

Next, it can be heat treated without pretreatment. The inorganic synthetic medium in which the chloride-based impurities are trapped is intended to be produced in a stable form, that is, in a solid form, preferably in the form of a solid glass. The inorganic synthetic medium in which the chloride- But it is not limited thereto. At this time, since the chloride-based impurity-containing inorganic synthetic medium additionally contains a glass solidification medium, it has an advantage that there is no separate pretreatment for production in solid form, that is, no separate solidification medium injection.

That is, after the heat treatment, the inorganic synthetic medium in which the chloride-based impurities are trapped may exist in a solid form.

According to the present invention, an inorganic synthetic medium containing a composite oxide containing silicon (Si), aluminum (Al), lithium (Li) and boron (B) The electrolyte can be immediately reused without taking out the electrolyte, and the amount of waste due to the electrolyte can be minimized.

In addition, the separated chloride-based impurities can be produced in a stable form (solid state form) by being heat-treated in a state of being trapped in an inorganic synthetic medium without additional pretreatment, that is, without addition of additives such as a solidification medium, And advantages in raw material aspect.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are provided only for the purpose of easier understanding of the present invention, and the present invention is not limited by the following examples.

[ Example ]

Example  One

After dissolving boric acid (H ₃ BO ₃ ), aluminum chloride (AlCl ₃ .6H ₂ O) and lithium hydroxide (LiOH) in distilled water (DI-Water) at room temperature and mixing them, tetraethylorthosilicate (TEOS) Dissolved in ethanol, reacted with each other, and the precipitate was separated by filtration under reduced pressure. Thereafter, it was dried at 150 ° C. for 2 hours, heat-treated at 650 ° C. for 10 hours, and pulverized to a size of 100 μm or less to prepare an inorganic synthetic medium. At this time, the composition of the inorganic synthetic medium was 39.5 wt% of SiO ₂ , 26.4 wt% of Al ₂ O ₃ , 21.0 wt% of Li ₂ O, and 13.1 wt% of B ₂ O ₃ .

1 is a graph showing an XRD pattern analysis result of an inorganic synthetic medium prepared according to Example 1. Fig.

As shown in FIG. 1, it was confirmed that the inorganic synthetic medium prepared according to Example 1 contains Li ₂ Al ₂ Si ₃ O ₁₀ . Meanwhile, in the inorganic synthetic medium prepared in Example 1, B ₂ O ₃ is a bar, XRD pattern analysis XRD peak to only a small amount is expected to be in the amorphous form did not confirm the presence of B ₂ O ₃ is a bond The presence of B-O bond was confirmed by FT-IR analysis of morphology.

Example  2

A simulated waste electrolyte was prepared considering the waste electrolytes generated in the electrolytic recovery process of spent fuel pyro processing. At this time, 2 kg of LiCl-KCl eutectic salt containing 5 wt% of simulated radionuclide chloride (NdCl ₃ ) was used as a simulated waste electrolyte. First, the simulated waste electrolytes were melted at 450 DEG C, a flange equipped with a porous crucible equipped with a stirrer and equipped with an inorganic synthetic medium was mounted on the reactor, and then a porous crucible was charged into the eutectic salt. At this time, 175.0 g of the inorganic synthesis medium prepared in Example 1 was supported on the crucible, and the stirrer was operated at a speed of 150 rpm for about 2 hours to allow the inorganic synthetic medium and NdCl ₃ to react with each other. The crucible was then removed from the eutectic salt and the eutectic salt in the reactor was cooled to room temperature. The extracted crucible was subjected to volatilization and condensation of the eutectic salt in the crucible in a reduced pressure volatilization / condensation recovery apparatus having a temperature gradient of 50 to 900 ° C, thereby separating the inorganic synthetic medium and the eutectic salt in which the NdCl ₃ was trapped in the crucible. The separated inorganic synthetic media were then heat treated at about 1450 ° C for about 2 hours to produce a glassy solid form. At this time, the removal rate of NdCl ₃ was calculated by the following formula 1, and it was confirmed that the removal rate of NdCl ₃ was about 99%:

[Equation 1]

Removal of NdCl ₃ = [(crucible charged before eutectic salt content within NdCl ₃ - after the crucible out eutectic salt within NdCl ₃ content) / (the crucible before charging molten salt in NdCl ₃ content)] × 100.

2 is a photograph showing the inorganic synthetic material in (a) an inorganic synthetic medium, (b) an inorganic synthetic medium in which NdCl ₃ is captured, and (c) a glass solidified form in Example 2.

As shown in Fig. 2 (c), it was confirmed that the separated inorganic synthetic medium in the form of glass solidified body was uniformly produced in the outer shape.

3 is a graph showing an XRD pattern analysis result of a mixture of an inorganic synthetic medium in which NdCl ₃ is captured and a remaining inorganic synthetic medium in which NdCl ₃ is not captured in Example 2. FIG.

As shown in FIG. 3, it can be confirmed that the inorganic synthetic medium containing NdCl ₃ in Example 2 contains a compound of LiNdSiO ₄ , and the remaining inorganic synthetic medium (without NdCl ₃ trapped) And a compound of Li ₂ Al ₂ Si ₃ O ₁₀ to be carried out. Meanwhile, in the inorganic synthetic medium prepared in Example 1, B ₂ O ₃ is a bar, XRD pattern analysis XRD peak to only a small amount is expected to be in the amorphous form did not confirm the presence of B ₂ O ₃ is a bond The presence of B-O bond was confirmed by FT-IR analysis of morphology.

4 is a graph showing the SEM analysis results of the inorganic synthetic medium separated in the form of a free solid in Example 2. FIG.

As shown in FIG. 4, it was confirmed that the inorganic synthetic media isolated in the form of free solid form in Example 2 were homogeneously distributed without phase separation, and due to the trapping of NdCl ₃ , Al, Si, Nd and O as elements , While element B was excluded from the analysis of the distribution within the glassy solid because it is an element that can not be analyzed by SEM-EDS.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (10)

(Si), aluminum (Al), lithium (Li) and boron (B)
15 to 25 parts by weight of silicon (Si), 5 to 15 parts by weight of aluminum (Al), 10 to 20 parts by weight of lithium (Li), and boron (B), based on 100 parts by weight of the total composite oxide, 1 part by weight to 10 parts by weight,
An inorganic synthetic medium for separating chlorine-based impurities in the waste electrolytes generated in an electrolytic process and then solidifying the glass without injecting a separate solidification medium.
delete The method according to claim 1,
Wherein the chloride-based impurity comprises at least one nuclide element selected from the group consisting of alkaline earth metals, rare earth metals and transuranic elements (TRU).
(a) charging an inorganic synthetic medium containing silicon (Si), aluminum (Al), lithium (Li) and boron (B) -containing complex oxides into the waste electrolytes generated in the electrolytic apparatus;
(b) separating the inorganic synthetic medium trapping the chloride-based impurities from the spent electrolyte after the inorganic synthetic medium is reacted with the chloride-based impurities contained in the waste electrolytic solution to purify the waste electrolytic solution; And
(c) separating the residual salt contained in the inorganic synthetic medium in which the separated chloride-based impurities are trapped, and then heat-treating the residue by heat treatment at a temperature of 1400 to 1500 ° C without injecting a separate solidification medium, ,
15 to 25 parts by weight of silicon (Si), 5 to 15 parts by weight of aluminum (Al), and 10 to 20 parts by weight of lithium (Li) based on 100 parts by weight of the composite oxide in the step (a) And 1 part by weight to 10 parts by weight of boron (B).
Separation and solidification of chloride - based impurities in waste electrolytes generated in electrolytic process.
5. The method of claim 4,
In step (a) the waste electrolytes method, separation and solidification, including molten salt selected from the group consisting of LiCl-KCl, LiF-KF and _{Li 2 CO 3 -K 2 CO 3} .
5. The method of claim 4,
Wherein the charging in the step (a) is carried out while the inorganic synthetic medium is supported on the porous crucible, and the porous crucible is mounted on the flange formed in the upper part of the reactor in the electrolytic apparatus.
5. The method of claim 4,
Wherein the reaction in step (b) is performed by stirring at a speed of 100 rpm to 200 rpm.
5. The method of claim 4,
The inorganic synthetic medium in which the chloride-based impurities are trapped in the step (c) is selected from the group consisting of a lithium-silicon (Si) oxide containing a nuclide element, an aluminum-silicon (Si) oxide containing a nuclide element, ) -Silicon (Si) oxide or silicon-containing silicon (Si) oxide.



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