KR102577113B1 - Zirconium recovery process and method for treating waste zirconium - Google Patents

Abstract

The present invention relates to a zirconium recovery process and a method of treating waste zirconium using the same. One aspect of the present invention includes the steps of electrolytic refining a zirconium (Zr) alloy using molten chloride salt as an electrolyte; Recovering ZrCl electrodeposited on the electrode surface through the electrolytic refining; and pyrolyzing the recovered ZrCl to obtain zirconium.

Description

Zirconium recovery process and waste zirconium disposal method {ZIRCONIUM RECOVERY PROCESS AND METHOD FOR TREATING WASTE ZIRCONIUM}

The present invention relates to a zirconium recovery process and a method for processing waste zirconium using the same.

Zirconium and zirconium alloys are widely used in commercial nuclear reactors due to their low thermal neutron absorption cross-section and excellent mechanical properties.

During reactor operation, zirconium alloys can become intermediate or class C radioactive waste due to the infiltration of actinides and fission products and radioactivity of impurities, but these components account for very small amounts.

If high-purity zirconium could be recovered from irradiated zirconium alloys, the beta-ray emission of zirconium radioisotopes would be weakened, and the final disposal volume of intermediate-level radioactive waste could be greatly reduced by being treated as low-level radioactive waste in the nuclear industry or conditionally recycled. will be. Additionally, recovered zirconium can be recycled back into the nuclear industry.

Accordingly, various studies are being conducted to find methods for separating high-purity zirconium metal from radioactive zirconium alloy.

For example, a method of directly extracting zirconium from waste zirconium alloy through electrolytic refining based on LiCl-KCl molten salt has been studied.

However, this method has problems depending on the type of zirconium electrodeposited on the electrode. That is, as the zirconium metal electrodeposition is not dense and is formed in a dendritic form, the rate of separation from the electrode is large, ultimately reducing the recovery rate. Additionally, during electrodeposition of zirconium metal, ZrCl form is also co-electrodeposited, thereby reducing the purity of the recovered zirconium metal.

Therefore, there is a need to develop a zirconium recovery process that can increase the purity and recovery rate of zirconium recovered from zirconium alloy.

The above-mentioned background technology is possessed or acquired by the inventor in the process of deriving the disclosure of the present application, and cannot necessarily be said to be known technology disclosed to the general public before the present application.
[Prior art literature]
[Non-patent literature]
JYPark et al., J. of The Electrochemical Society, Vol.161, No.3, pp.H94-H104 (2013.12.27.)

The present invention is intended to solve the above-mentioned problems, and the purpose of the present invention is to provide a zirconium recovery process that can recover high purity zirconium at a high recovery rate from zirconium alloy.

However, the problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

One aspect of the present invention includes electrorefining a zirconium (Zr) alloy using molten chloride salt as an electrolyte; Recovering ZrCl electrodeposited on the electrode surface through the electrolytic refining; and pyrolyzing the recovered ZrCl to obtain zirconium.

According to one embodiment, the chloride molten salt is LiCl-KCl, NaCl-KCl, LiCl-NaCl-CaCl ₂ -BaCl ₂ , NaCl-KCl-BaCl ₂ , CdCl _2, CdF _2, NdCl ₃ CeCl ₃ and LaCl ₃ It may include one or more selected from the group consisting of.

According to one embodiment, the electrolyte may include ZrCl ₄ in an amount of 1% to 10% by weight.

According to one embodiment, the electrolytic refining step may be performed at a temperature of 600 K to 800 K.

According to one embodiment, the electrolytic refining step may be performed by applying a voltage of -1.0 V to -2.0 V to the electrode compared to the Ag/AgCl reference electrode.

According to one embodiment, the electrode may include one or more selected from the group consisting of tungsten (W), molybdenum (Mo), and stainless steel.

According to one embodiment, ZrCl electrodeposited on the electrode surface may include a layered structure.

According to one embodiment, the thermal decomposition may be performed at a pressure of 200 Pa to 250 Pa and a temperature of 800 K to 1500 K for 10 to 24 hours.

According to one embodiment, the reaction represented by the following reaction formula may be induced by the thermal decomposition.

[Reaction formula]

4ZrCl(s)→ZrCl ₄ (g)+3Zr(s)

According to one embodiment, the obtained zirconium may include an HCP structure or an FCC structure.

According to one embodiment, the obtained zirconium particles may have a diameter of 0.01 μm to 5 μm.

According to one embodiment, the zirconium alloy may include a waste zirconium alloy.

Another aspect of the present invention provides a method for processing waste zirconium, including the step of manufacturing the zirconium recovered through the recovery process into an ingot.

Another aspect of the present invention includes electrorefining a zirconium (Zr) alloy using molten chloride salt as an electrolyte; Recovering ZrCl electrodeposited on the electrode surface through the electrolytic refining; Obtaining zirconium by thermally decomposing the recovered ZrCl; Electrorefining the spent molten salt from which the ZrCl is recovered using a liquid cadmium electrode to form a cadmium alloy; and fractional distillation of the cadmium alloy to separate the alloy ions remaining in the waste molten salt into a solid phase.

According to one embodiment, the alloy ions remaining in the spent molten salt may include actinide-based ions.

According to one embodiment, the spent molten salt from which the cadmium alloy is recovered may be reused as the electrolyte.

The zirconium recovery process according to the present invention increases the recovery rate by recovering zirconium in the form of ZrCl with a dense structure during electrolytic refining, and obtains zirconium metal through a thermal decomposition reaction of the recovered ZrCl, thereby increasing the purity of the finally recovered zirconium. There is an effect.

In addition, the method for processing waste zirconium according to the present invention recovers high-purity zirconium at a high recovery rate, recovers and reuses the electrolyte distilled during the thermal decomposition process, and recovers zirconium and then disposes of it through a waste molten salt regeneration process. This has the effect of separating and disposing only the alloy elements in the molten salt and reusing the molten salt.

1 is a flow chart of a zirconium recovery process according to an embodiment of the present invention.
Figure 2 is a schematic diagram of a vacuum distillation furnace for performing a thermal decomposition reaction, according to an embodiment of the present invention.
Figure 3 is an XRD pattern of ZrCl electrodeposited on a tungsten electrode (cathode) before and after pyridine washing.
Figure 4 is an optical image of ZrCl electrodeposited on a tungsten electrode (cathode) and an SEM image before pyridine washing.
Figure 5 is an XRD pattern and SEM image of zirconium metal powder produced after thermal decomposition in Examples 1 to 3.
Figure 6 is an XRD pattern and SEM image of zirconium metal powder produced after thermal decomposition in Examples 4 to 6.
Figure 7 is an XRD pattern and SEM image of zirconium metal powder produced after thermal decomposition in Examples 7 to 9.
Figure 8 is a graph showing the concentration of potassium measured in zirconium produced after thermal decomposition reaction.
Figure 9 is a Raman spectrum of Example 4, Example 6, Example 7, Example 9, and Zr heat-treated at 227 Pa to 240 Pa.

Hereinafter, embodiments will be described in detail with reference to the attached drawings. However, various changes can be made to the embodiments, so the scope of the patent application is not limited or limited by these embodiments. It should be understood that all changes, equivalents, or substitutes for the embodiments are included in the scope of rights.

The terms used in the examples are for descriptive purposes only and should not be construed as limiting. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by a person of ordinary skill in the technical field to which the embodiments belong. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and unless explicitly defined in the present application, should not be interpreted in an ideal or excessively formal sense. No.

In addition, when describing with reference to the accompanying drawings, identical components will be assigned the same reference numerals regardless of the reference numerals, and overlapping descriptions thereof will be omitted. In describing the embodiments, if it is determined that detailed descriptions of related known technologies may unnecessarily obscure the gist of the embodiments, the detailed descriptions are omitted.

Additionally, in describing the components of the embodiment, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish the component from other components, and the nature, sequence, or order of the component is not limited by the term. When a component is described as being "connected," "coupled," or "connected" to another component, that component may be directly connected or connected to that other component, but there is no need for another component between each component. It should be understood that may be “connected,” “combined,” or “connected.”

Components included in one embodiment and components including common functions will be described using the same names in other embodiments. Unless stated to the contrary, the description given in one embodiment may be applied to other embodiments, and detailed description will be omitted to the extent of overlap.

The present invention is related to a research project sponsored by Korea Hydro & Nuclear Power (low-level metal waste technology development and commercialization feasibility study, 2020-06-01 ~ 2021-05-31).

One aspect of the present invention includes electrorefining a zirconium (Zr) alloy using molten chloride salt as an electrolyte; Recovering ZrCl electrodeposited on the electrode surface through the electrolytic refining; and pyrolyzing the recovered ZrCl to obtain zirconium.

The zirconium recovery process according to the present invention has the effect of recovering high-purity zirconium metal at a high recovery rate through an electrolytic refining process and a thermal decomposition process.

Hereinafter, the zirconium recovery process according to the present invention will be described in detail step by step.

electrolytic refining step

The first step in the zirconium recovery process according to the present invention is the electrolytic refining step.

In general, electrolytic refining, also called electrolytic refining, is a method of increasing the purity of metal gold using electrolysis. When two electrodes are placed in an electrolyte solution using a piece of low-purity metal as the anode and a thin plate of an appropriate metal as the cathode and an electric current flows, the high-purity metal precipitates on the cathode plate, and impurities accumulate at the bottom of the electrolytic cell.

In the zirconium recovery process according to the present invention, zirconium alloy is electrolytically refined using molten chloride salt as an electrolyte.

According to one embodiment, the chloride molten salt is LiCl-KCl, NaCl-KCl, LiCl-NaCl-CaCl ₂ -BaCl ₂ , NaCl-KCl-BaCl ₂ , CdCl _2, CdF _2, NdCl ₃ CeCl ₃ and LaCl ₃ It may include one or more selected from the group consisting of.

Preferably, the chloride molten salt may include LiCl-KCl.

According to one embodiment, the electrolyte may include ZrCl ₄ in an amount of 1% to 10% by weight.

Preferably, the electrolyte may contain 1% to 5% by weight of ZrCl ₄ , and more preferably, 1% to 3% by weight.

If the content of ZrCl ₄ in the electrolyte is less than the above range, ZrCl may be formed in a dendritic form on the electrode surface or may be detached from the electrode, which may reduce the process speed of electrolytic refining.

On the other hand, if the content of ZrCl ₄ in the electrolyte exceeds the above range, ZrCl in a layered form may not be generated.

According to one embodiment, the electrolytic refining step may be performed at a temperature of 600 K to 800 K.

Preferably, the electrolytic refining step may be performed at a temperature of 650 K to 800 K, more preferably, it may be performed at a temperature of 700 K to 800 K, and even more preferably, It may be performed at a temperature of 730 K to 780 K.

The temperature range during electrolytic refining may be the optimal range for depositing high-purity ZrCl in a dense layered form on the electrode surface.

If the temperature during electrolytic refining is below the above range, ZrCl may not be formed and the process speed may be reduced, and if it exceeds the above range, Zr metal may be co-electrodeposited.

According to one embodiment, the electrolytic refining step may be performed by applying a voltage of -1.0 V to -2.0 V to the electrode compared to the Ag/AgCl reference electrode.

Preferably, it may be performed by applying a voltage of -1.0 V to -1.5 V compared to the Ag/AgCl reference electrode, and more preferably, it may be performed by applying a voltage of -1.0 V to -1.3 V. , and even more preferably, may be performed by applying a voltage of -1.0 V to -1.2 V.

If the voltage exceeds the above range, ZrCl and Zr are formed together on the electrode surface, resulting in a problem that only ZrCl cannot be recovered.

Additionally, the Zr metal formed on the electrode surface may reduce current efficiency due to a reaction with Zr ⁴⁺ (Zr + Zr ⁴⁺ ↔ Zr ²⁺ ), and the final recovery rate of Zr metal may decrease.

Specifically, when the applied voltage has a negative potential value smaller than the above range, Zr metal and ZrCl may co-electrodeposit, and when the applied voltage has a negative potential value exceeding the above range, the process speed is reduced or ZrCl electrodeposited. This may not happen.

In one embodiment of the present invention, the temperature and voltage conditions during electrolytic refining may serve as key factors for electrodepositing only ZrCl on the electrode surface.

Conventionally, when Zr metal is recovered directly from the electrode surface, the recovered Zr metal not only has a weak structure, but is also lost during the electrolytic refining process, resulting in a low recovery rate.

Therefore, the zirconium recovery process according to the present invention allows only ZrCl to be electrodeposited on the electrode surface through electrolytic refining and thermally decomposes the electrodeposited ZrCl, ultimately allowing high purity zirconium metal to be obtained with a high recovery rate.

According to one embodiment, the electrode may include one or more selected from the group consisting of tungsten (W), molybdenum (Mo), and stainless steel.

According to one embodiment, the electrode is a cathode and may include tungsten.

The electrode containing tungsten not only clearly separates the ZrCl formed on the surface through electrolytic refining, but also does not generate intermetallic formations because a chemical reaction with ZrCl does not occur, and has the advantage of excellent scraping characteristics.

Excellent scraping properties may be required to ensure high purity electrodeposits.

The stainless steel has the advantage of excellent mechanical properties, but its scraping properties may be relatively poor compared to tungsten and molybdenum.

The surface area of the electrode and the amount of zirconium alloy that can be processed through electrorefining may be proportional.

ZrCl recovery step

ZrCl electrodeposited on the electrode surface through electrolytic refining is recovered for thermal decomposition.

According to one embodiment, recovering ZrCl electrodeposited on the electrode surface through electrolytic refining; Afterwards, a step of washing the recovered ZrCl may be further included.

According to one embodiment, the washing may be performed using anhydrous pyridine.

Through the washing, the electrolyte remaining in the electrodeposited ZrCl can be removed.

The electrolyte remaining after the washing may be distilled and removed during a later thermal decomposition process.

According to one embodiment, ZrCl electrodeposited on the electrode surface may include a layered structure.

ZrCl electrodeposited on the electrode surface is formed in a dense layered structure and may not contain dendrites.

ZrCl electrodeposited in the dense layered structure does not escape from the electrode during electrolytic refining, thereby increasing the recovery rate of zirconium.

According to one embodiment, ZrCl electrodeposited on the electrode surface may include an octahedral crystal structure.

pyrolysis step

The thermal decomposition step is a step of thermally decomposing the recovered ZrCl electrodeposit to obtain zirconium.

The pyrolysis step may be performed in a high temperature vacuum process and, according to one embodiment, in a vacuum distillation furnace.

According to one embodiment, the thermal decomposition may be performed at a pressure of 200 Pa to 250 Pa and a temperature of 800 K to 1500 K for 10 to 24 hours.

If, in the thermal decomposition step, the pressure is outside the above range, the process time may increase, the process temperature may increase, or zirconium crystallization may be insufficient.

Additionally, if the temperature is outside the above range, the process time may increase, zirconium crystallization may be insufficient, or residual electrolyte removal may be insufficient.

Furthermore, if the reaction time is outside the above range, residual electrolyte removal may be insufficient or crystallization of zirconium may occur insufficiently.

According to one embodiment, the thermal decomposition may be performed at a pressure of 200 Pa to 250 Pa and a temperature of 1300 K to 1500 K for 10 to 24 hours.

The pressure, temperature, and time conditions during thermal decomposition may be optimal conditions for increasing the purity of zirconium metal.

If, in the thermal decomposition step, the reaction is performed beyond the pressure range or below the time range, crystallization of zirconium may be insufficient.

Additionally, in the thermal decomposition step, if the reaction proceeds below the temperature range, residual electrolyte may not be removed and zirconium may be insufficiently crystallized. On the other hand, if the reaction proceeds beyond the above temperature range, process costs may increase.

In the thermal decomposition step, the higher the temperature and the lower the pressure, the faster the thermal decomposition reaction rate may be.

According to one embodiment, the reaction represented by the following reaction formula may be induced by the thermal decomposition.

[Reaction formula]

4ZrCl(s)→ZrCl ₄ (g)+3Zr(s)

According to one embodiment, during the thermal decomposition, the remaining electrolyte may be removed by distillation.

According to one embodiment, the obtained zirconium may include an HCP structure or an FCC structure.

According to one embodiment, as the temperature increases and the reaction time increases during thermal decomposition, the proportion of the FCC structure may increase.

This may be because when ZrCl is thermally decomposed above the activation temperature, zirconium in the HCP structure begins to form, and a phase transition from HCP to FCC is induced by thermal residual stress between particles.

According to one embodiment, the obtained zirconium may include only an FCC structure.

According to one embodiment, the obtained zirconium metal may be in the form of rectangular or circular particles.

According to one embodiment, the obtained zirconium particles may have a diameter of 0.01 μm to 5 μm.

According to one embodiment, the obtained zirconium particles may have a diameter of 0.1 μm to 2 μm.

Zirconium obtained through thermal decomposition can be formed more finely at low pressure.

According to one embodiment, the zirconium alloy may include a waste zirconium alloy.

The waste zirconium may include irradiated zirconium and may include radioactive waste.

Another aspect of the present invention provides a method for processing waste zirconium, including the step of manufacturing the zirconium recovered through the recovery process into an ingot.

The recovery process according to the present invention has the feature of being able to recover high purity zirconium at a high recovery rate from zirconium alloy or waste zirconium.

High purity zirconium recovered with high recovery rate can be manufactured into ingots through arc melting.

The zirconium ingots can be recycled in the nuclear industry and disposed of as low-level radioactive waste.

Another aspect of the present invention includes electrorefining a zirconium (Zr) alloy using molten chloride salt as an electrolyte; Recovering ZrCl electrodeposited on the electrode surface through the electrolytic refining; Obtaining zirconium by thermally decomposing the recovered ZrCl; Electrorefining the spent molten salt from which the ZrCl is recovered using a liquid cadmium electrode to form a cadmium alloy; and fractional distillation of the cadmium alloy to separate the alloy ions remaining in the waste molten salt into a solid phase.

According to one embodiment, the alloy ions remaining in the spent molten salt may include actinide-based ions.

According to one embodiment, the cadmium alloy may be an actinide-cadmium alloy.

The actinide-cadmium alloy can be separated into actinide and cadmium through vacuum distillation.

The separated actinide can be discarded, and the recovered cadmium can be reused as an electrode for purifying spent molten salt.

According to one embodiment, the alloy elements remaining in the spent molten salt may include one or more selected from the group consisting of Sn, Cr, Fe, and Co.

According to one embodiment, the spent molten salt from which the cadmium alloy is recovered may be reused as the electrolyte.

1 is a flow chart of a zirconium recovery process according to an embodiment of the present invention.

Referring to Figure 1, waste zirconium alloy is recovered in the form of ZrCl through electrolytic refining, and the recovered ZrCl electrodeposit is converted into Zr metal through thermal decomposition. At this time, the residual electrolyte deposited with ZrCl is removed through a distillation process.

Recovered Zr metal ingots can be recycled or disposed of as low-level or extremely low-level waste.

During electrolytic refining, there are alloy elements that are not dissolved in the electrolyte, which can be recovered from the spent molten salt and disposed of as intermediate level waste.

The waste molten salt remaining after electrolytic refining is electrodeposited using a liquid cadmium electrode (Cd) by applying electric current to dissolved ions (actinide, etc.) in the waste molten salt. When the electrodeposited metals exceed their solubility in the liquid cadmium electrode, they form a cadmium alloy. After separating the cadmium alloy, the cadmium component can be removed from the cadmium alloy through a distillation process to separate and recover alloy elements (metals such as actanide) in a solid phase.

Distilled cadmium can be recycled as a liquid metal electrode in the waste molten salt regeneration process, and molten salt from which ions have been removed through the waste molten salt regeneration process can be recycled as an electrolyte for electrolytic refining.

Hereinafter, the present invention will be described in more detail through examples and comparative examples.

However, the following examples are only for illustrating the present invention, and the content of the present invention is not limited to the following examples.

<Example> Zirconium recovery process

1) Electrolytic refining

LiCl-KCl-10% by weight ZrCl ₄ molten salt was prepared as salt mixture pellets.

Anhydrous ZrCl ₄ and LiCl-KCl eutectic salt (Sigma-Aldrich, 99.99%) were sequentially placed in a quartz tube cell with an inner diameter of 36 mm and a length of 340 mm. After rapidly dissolving the reagent at 873K, the concentration of Zr was analyzed by ICP-OES. Based on the results, more LiCl-KCl eutectic salt was added to dilute the salt mixture to the desired salt composition (LiCl-KCl-2% by weight ZrCl ₄ ).

A tungsten working electrode with a diameter of 3.175 mm (Alpha Aesar, 99.99%) and two tungsten counter electrodes with a diameter of 4 mm (Alpha Aesar, 99.99%) were used to ensure that the surface area of the counter electrode was larger than that of the working electrode; The molten diluted salt was obtained and then inserted into the same quartz tube cell.

The reference electrode consisted of Ag wire (Alfa Aesar, 99.99%) and LiCl-KCl-1 wt% AgCl (Alpha Aesar, 99.99%) in a Pyrex tube. The temperature of the electrochemical cell was maintained at 723 ± 1 K and controlled by the furnace's proportional-integral-derivative (PID) system.

To recover ZrCl, a voltage of -1.1 V (vs. Ag/AgCl) was applied to the cathode electrode. The electrochemical cell was monitored and controlled using an AMETEK Solartron 1287A with CorrWare software. ZrCl was repeatedly recovered under the same conditions and washed with anhydrous pyridine (Alpha Aesar, 99.5+%) to remove electrolyte before pyrolysis.

2) Pyrolysis

The recovered ZrCl was introduced into a vacuum distillation furnace and a thermal decomposition reaction was performed.

The temperature was controlled by a PID system and an electric furnace, and the pressure was maintained by a vacuum pump line. The temperature was increased at a rate of 200 K/h, and after reaching the desired value, it was decreased in the range of 0.04-0.06 K/s for the conditions of 101.3 kPa and 227 Pa to 240 Pa. The line was connected to a ball valve so the pressure changed instantly.

In order to determine the effect of reaction temperature, pressure, and reaction time during thermal decomposition, the thermal decomposition reaction was performed by changing each condition. At this time, the reaction time is the time maintained at the target temperature.

The conditions for each pyrolysis reaction are shown in Table 1.

Temperature (K) Pressure (Pa) reaction time (h) Example 1 873 101325 12 Example 2 873 227-240 12 Example 3 873 227-240 24 Example 4 1073 101325 12 Example 5 1073 227-240 12 Example 6 1073 227-240 24 Example 7 1373 101325 12 Example 8 1373 227-240 12 Example 9 1373 227-240 24

Figure 2 is a schematic diagram of a vacuum distillation furnace for performing a thermal decomposition reaction, according to an embodiment of the present invention.

Referring to Figure 2, it can be seen that the vacuum distillation furnace consists of two vertically positioned sections.

Here, the lower part is a reactor section containing a tantalum crucible (10) with a diameter of 30 mm and a height of 40 mm to contain the sample, and the upper part is a reactor section to capture the gas evaporated by coagulation due to the temperature difference between the two sections. This is the car recovery section (20).

The head section 30 is located at the top of the furnace and serves as a separating barrier to the glove box atmosphere. It is also a conduit for the two K-type thermocouple lines and the vacuum/purge (40) line from the other two sections.

The internal atmosphere was controlled by a vacuum/purge 40 line connected to a cold trap and vacuum pump. Additionally, a cold trap was installed in the vacuum/purge (40) line to remove residual chemical gases during the reaction.

The furnace was housed in a stainless steel container with a diameter of 114 mm and a height of 500 mm. The highest temperature in the vacuum distillation furnace was 1473 K and the lowest pressure was 133 Pa.

<Experimental Example 1> Confirmation of composition and structure of electrodeposition material recovered through electrolytic refining

The composition and microstructure of the electrodeposition material recovered through electrolytic refining were analyzed by XRD and SEM.

XRD measurements were performed using a high-power The acquired spectra were analyzed with PDXL-2 software (Rigaku).

The morphology of the sample was obtained by SEM (Hitachi, S-4800) in secondary electron (SE) mode with an accelerating voltage of 10 kV.

Figure 3 is an XRD pattern of ZrCl electrodeposited on a tungsten electrode (cathode) before and after pyridine washing.

Figure 3a is an XRD pattern of ZrCl electrodeposited on a tungsten electrode (cathode) before pyridine washing, and Figure 3b is an XRD pattern of ZrCl electrodeposited on a tungsten electrode (cathode) after pyridine washing.

Referring to Figure 3, it can be seen that ZrCl was successfully recovered through electrolytic refining.

In addition, it can be seen that LiCl, which has relatively high solubility, was removed after washing, but KCl was deposited due to its low solubility.

Figure 4 is an optical image of ZrCl electrodeposited on a tungsten electrode (cathode) and an SEM image before pyridine washing.

Figure 4a is an optical image of ZrCl electrodeposited on a tungsten electrode (cathode), and Figure 4b is an SEM image of ZrCl electrodeposited on a tungsten electrode (cathode) before pyridine washing.

Referring to FIG. 4, it can be confirmed that ZrCl was deposited on the tungsten electrode without dendritic growth, and that it had the form of a flat layer.

Additionally, no particles were observed at the bottom of the quartz tube cell.

<Experimental Example 2> Confirmation of crystallographic structure of zirconium obtained through thermal decomposition

The crystallographic structure of zigconium obtained through thermal decomposition was analyzed by XRD and SEM.

XRD measurements were performed using a high-power The acquired spectra were analyzed with PDXL-2 software (Rigaku).

The morphology of the sample was obtained by SEM (Hitachi, S-4800) in secondary electron (SE) mode with an accelerating voltage of 10 kV.

Figure 5 is an XRD pattern and SEM image of zirconium metal powder produced after thermal decomposition in Examples 1 to 3.

Figure 5a is an XRD pattern and SEM image of the zirconium metal powder produced after thermal decomposition in Example 1, Figure 5b is an XRD pattern and SEM image of the zirconium metal powder produced after thermal decomposition in Example 2, and Figure 5c is, These are the XRD pattern and SEM image of the zirconium metal powder produced after thermal decomposition in Example 3.

Referring to FIG. 5, it can be seen that in the XRD pattern under the 873 K condition, the ZrCl peak did not appear and several small Zr metal peaks appeared. In addition, it can be seen that the lower the reaction pressure and the longer the reaction time, the more clearly the Zr metal peak appears.

Therefore, it can be expected that although thermal decomposition occurred, crystallization of Zr metal was insufficient.

For Examples 1 and 2, HCP-Zr metal peaks (ICDD No. 01-088-0665, 01-089-3045) were confirmed, and for Example 3, FCC-Zr metal peak (ICDD No. 01- 088-2329) was confirmed. Additionally, in Examples 1 to 3, KCl remained even after the thermal decomposition reaction.

Referring to the SEM image in Figure 5, the particles produced in Examples 1 and 2 appeared in rectangular and circular shapes on a layered structure, and the particle size was about 0.5 ㎛ in Example 1 and 0.1 in Example 2. It was less than ㎛. This was thought to be due to the formation of more nucleation points under lower pressure conditions, resulting in finer particles.

Additionally, the degree of growth increased and the size of the particles increased as they merged with each other.

Figure 6 is an XRD pattern and SEM image of zirconium metal powder produced after thermal decomposition in Examples 4 to 6.

Figure 6a is an XRD pattern and SEM image of the zirconium metal powder produced after thermal decomposition in Example 4, Figure 6b is an XRD pattern and SEM image of the zirconium metal powder produced after thermal decomposition in Example 5, and Figure 6c is, These are the XRD pattern and SEM image of the zirconium metal powder produced after thermal decomposition in Example 6.

Referring to FIG. 6, it can be seen that when the temperature rises to 1073K, the Zr metal peak appears more significantly than at 873K. This means that the crystallization of Zr metal was better achieved.

In particular, the height of the KCl peak was significantly reduced, and in Example 6, the KCl peak completely disappeared.

In Examples 4 and 6, HCP-Zr and FCC-Zr peaks were confirmed together, but in Example 6, only the FCC-Zr peak was confirmed and the average height increased.

Referring to the SEM image in FIG. 6, it can be seen that when the temperature is 1073 K, the layered structure that appeared at a temperature of 873 K is completely destroyed.

In addition, almost all the particles were very fine, few particles reached the size of 2-4 μm, and it can be seen that the particles were generally well developed and connected to nearby particles. In particular, the particles of Example 6 showed specificity and independence.

Figure 7 is an XRD pattern and SEM image of zirconium metal powder produced after thermal decomposition in Examples 7 to 9.

Figure 7a is an XRD pattern and SEM image of the zirconium metal powder produced after thermal decomposition in Example 7, Figure 7b is an XRD pattern and SEM image of the zirconium metal powder produced after thermal decomposition in Example 8, and Figure 7c is, These are the XRD pattern and SEM image of the zirconium metal powder produced after thermal decomposition in Example 9.

Referring to Figure 7, it can be seen that in all cases where the temperature was 1373 K, the FCC-Zr peak appeared without the KCl peak.

Referring to the SEM image in FIG. 7, it can be seen that round crystals with a clean surface appear in all cases where the temperature is 1373 K, especially under low pressure conditions.

Through this, it can be seen that when the temperature is 1373 K, the crystallinity of the particles is good and agglomeration is relatively low.

<Experimental Example 3> Residual mass analysis of electrolyte in produced zirconium

After the zirconium produced after the thermal decomposition reaction was washed with pyridine, the concentration of potassium was analyzed by ICP-OES (Varian, 700-ES) to measure the concentration of KCl, the only remaining electrolyte.

Figure 8 is a graph showing the concentration of potassium measured in zirconium produced after thermal decomposition reaction.

Referring to Figure 8, it can be seen that the amount of potassium distilled increases as the temperature is increased and the pressure is lowered.

In addition, it can be confirmed that through distillation of the electrolyte, the purity of Zr metal can be improved to a high level under the conditions of 1373K and 227 Pa to 240 Pa.

<Experimental Example 4> Confirmation of crystal phase of generated zirconium

In order to confirm the crystal phase of the produced zirconium, a spectrum was obtained using Raman spectroscopy and then compared with the ZrO ₂ spectrum.

Confocal Raman spectroscopy (WITec, alpha300R) was performed with a wavelength of 532 nm laser, at 10 mW power, 1800 lines/mm grating, 5 s integration time and 10× accumulation.

According to previous studies, the spectra of monoclinic and tetragonal ZrO ₂ are 145, 172, 185, 217, 269, 312, 325, 339, 376, 457, 460, 474, 500, 532, 555 and 639 cm ^-1 A peak appears at

Figure 9 is a Raman spectrum of Example 4, Example 6, Example 7, Example 9, and Zr heat-treated at 227 Pa to 240 Pa.

Referring to FIG. 9, no peaks were observed in the Raman spectra of the examples and heat-treated zirconium, which is consistent with the reported spectrum of pure zirconium.

In particular, Example 9 showed a spectrum similar to the Raman spectrum of heat-treated Zr, but no peak appearing in ZrO ₂ was observed.

Although the embodiments have been described with limited drawings as described above, those skilled in the art can apply various technical modifications and variations based on the above. For example, the described techniques are performed in a different order than the described method, and/or components of the described system, structure, device, circuit, etc. are combined or combined in a different form than the described method, or other components are used. Alternatively, appropriate results may be achieved even if substituted or substituted by an equivalent.

Therefore, other implementations, other embodiments, and equivalents of the claims also fall within the scope of the following claims.

10: Tantalum crucible
20: Secondary retrieval section
30: Head
40: Vacuum/Purge
50: Sample
100: Heating Furnace
200: Insulation

Claims (16)

Electrolytic refining of zirconium (Zr) alloy using molten chloride salt as an electrolyte;
Recovering ZrCl electrodeposited on the electrode surface through the electrolytic refining; and
Comprising: thermally decomposing the recovered ZrCl to obtain zirconium,
The thermal decomposition is carried out in a high-temperature vacuum process in a vacuum distillation furnace,
The thermal decomposition is performed at a pressure of 200 Pa to 250 Pa and a temperature of 1300 K to 1500 K for 10 to 24 hours.
Zirconium recovery process.
According to paragraph 1,
The chloride molten salt is,
Containing one or more selected from the group consisting of LiCl-KCl, NaCl-KCl, LiCl-NaCl-CaCl ₂ -BaCl ₂ , NaCl-KCl-BaCl ₂ , CdCl _2, CdF _2, NdCl ₃ CeCl ₃ and LaCl ₃ person,
Zirconium recovery process.
According to paragraph 1,
The electrolyte is,
Containing ZrCl ₄ in an amount of 1% to 10% by weight,
Zirconium recovery process.
According to paragraph 1,
The electrolytic refining step is,
Carried out at a temperature of 600 K to 800 K,
Zirconium recovery process.
According to paragraph 1,
The electrolytic refining step is,
This is performed by applying a voltage of -1.0 V to -2.0 V to the electrode compared to the Ag/AgCl reference electrode,
Zirconium recovery process.
According to paragraph 1,
The electrode is,
Containing one or more selected from the group consisting of tungsten (W), molybdenum (Mo) and stainless steel,
Zirconium recovery process.
According to paragraph 1,
ZrCl electrodeposited on the electrode surface includes a layered structure,
Zirconium recovery process.
delete According to paragraph 1,
By the thermal decomposition, a reaction represented by the following reaction equation is induced,
[Reaction formula]
4ZrCl(s)→ZrCl ₄ (g)+3Zr(s)
Zirconium recovery process.
According to paragraph 1,
The obtained zirconium is,
Comprising an HCP structure or an FCC structure,
Zirconium recovery process.
According to paragraph 1,
The diameter of the obtained zirconium particles is 0.01 μm to 5 μm,
Zirconium recovery process.
According to paragraph 1,
The zirconium alloy includes a waste zirconium alloy,
Zirconium recovery process.
Manufacturing the zirconium recovered through the recovery process of claim 1 into an ingot;
Including,
How to dispose of waste zirconium.
Electrolytic refining of zirconium (Zr) alloy using molten chloride salt as an electrolyte;
Recovering ZrCl electrodeposited on the electrode surface through the electrolytic refining;
Obtaining zirconium by thermally decomposing the recovered ZrCl;
Electrorefining the spent molten salt from which the ZrCl is recovered using a liquid cadmium electrode to form a cadmium alloy; and
Fractionally distilling the cadmium alloy to separate the alloy ions remaining in the spent molten salt into a solid phase,
The alloy ions remaining in the spent molten salt include actinide ions,
The thermal decomposition is carried out in a high-temperature vacuum process in a vacuum distillation furnace,
The thermal decomposition is performed at a pressure of 200 Pa to 250 Pa and a temperature of 1300 K to 1500 K for 10 to 24 hours.
Waste zirconium disposal method.
delete According to clause 14,
The spent molten salt from which the cadmium alloy was recovered,
which is reused as the electrolyte,
Waste zirconium disposal method.

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