KR102562722B1 - Anode for electrolysis, electrolytic cell comprising the same, and electrolysis process using the electrolytic cell - Google Patents

Abstract

The present invention relates to an anode included in an electrolytic cell for electrolysis of an aluminum-scandium master alloy, wherein a concave portion is formed at an end of the anode, and a discharge port for discharging by-product gas to the outside is formed in the concave portion. According to the present invention, an electrolytic cell for recovering an aluminum-scandium mother alloy is prevented from lowering the recovery rate of the aluminum-scandium mother alloy due to the presence of molten aluminum in the electrolyte in the form of liquid droplets in the electrolytic recovery process of the aluminum-scandium mother alloy. It has the effect of improving the recovery rate and reaction efficiency of scandium alloy.

Description

Anode for electrolysis, an electrolytic cell including the same, and an electrolysis method using the electrolytic cell

The present invention relates to an electrolytic anode for electrolysis of an aluminum-scandium mother alloy, an electrolytic bath including the same, and an electrolysis method using the electrolytic bath.

Rare earths are essential resources used in various fields such as magnets, phosphors, catalysts and abrasives, and China accounts for most of the world's rare earth exports. In 2010, due to the Senkaku clash between China and Japan, China restricted exports of rare earths for reasons of environmental and nature conservation. Let's face it, in 2011 the price of some rare earths soared more than fivefold. On the other hand, scandium (Sc, Scandium) with atomic number 21, which is classified as a similar rare earth element, is an alloy element that is added in small amounts to aluminum (Al, Aluminum) alloys. When the scandium is added in small amounts to aluminum alloys, mechanical properties of aluminum alloys It is reported to greatly improve weldability, corrosion resistance and elongation.

With this scandium metal reduction technology, a research team led by Professor Okabe of Tokyo University in Japan has recently proposed a scandium-containing aluminum alloy manufacturing process through electrolysis (electrolysis) (http://www.okabe.iis.u-tokyo.ac.jp/core-to -core/rmw/RMW3/slide/RMW3_20_Harata_T.pdf). In the case of electrolysis, the target metal to be reduced is obtained at the cathode by the electrochemical reaction of the cathode and anode in a molten salt state, and carbon dioxide or chlorine gas is generated at the anode. The main characteristics of the electrolysis process proposed by Professor Okabe are that scandium oxide (Sc ₂ O ₃ ) is used as a raw material, calcium chloride (CaCl ₂ ) and a eutectic salt of scandium oxide are used as the electrolyte, and molten aluminum is used as the cathode. And, the electrolysis process proceeds at a process temperature of 900 ° C.

1 is a view showing a cross section of an electrolytic cell used in a typical electrolysis process. The density of the molten aluminum negative electrode 40 used as the negative electrode is 2.375 g/cm ³ , and the density of chloride used as the electrolyte 70 is typically 2.0 to 2.1 g/cm ³ . Although the density of the molten aluminum is higher than that of the electrolyte, the density difference is not large. Therefore, the flow of molten aluminum occurs due to carbon dioxide, which is a by-product gas 60 generated from the anode 10 during the electrolytic reaction. Due to this, a part of the molten aluminum is mixed into the electrolyte, and the mixed molten aluminum exists in the form of droplets due to surface tension to generate aluminum droplets 50 . Due to the generation of the aluminum droplets, the content of aluminum used as the negative electrode is reduced, and there is a problem in that the recovery rate of the aluminum-scandium alloy finally recovered from the negative electrode is very low.

An object of the present invention is to provide an electrolytic anode with improved recovery rate and reaction efficiency, an electrolytic cell including the same, and an electrolysis method using the electrolytic cell.

According to an embodiment of the present invention, in an anode included in an electrolytic cell for electrolysis of an aluminum-scandium master alloy, a concave portion is formed at an end of the anode, and a discharge port for discharging by-product gas to the outside is formed in the concave portion. An anode for electrolysis is provided.

The concave portion may have a conical shape, an elliptical cone shape, a polygonal pyramidal shape, a truncated cone shape, an elliptical truncated cone shape, a polygonal pyramidal shape, a cylinder shape, an elliptical columnar shape, a polygonal columnar shape, a hemispherical shape, or a semi-ellipsoidal shape.

Two or more outlets may be formed in the concave portion.

The outlet may be formed in the center of the concave portion.

The outlet may have a maximum diameter of 1 mm or less.

According to another embodiment of the present invention, an electrolytic cell including the anode for electrolysis is provided.

The electrolytic cell may further include an electrolytic cell body filled with electrolyte, and an aluminum cathode disposed at the bottom of the electrolytic cell.

The electrolyte may be fluoride, chloride or a mixture thereof.

According to another embodiment of the present invention, providing an electrolysis method comprising the steps of supplying scandium oxide and an electrolyte to the electrolytic bath, heating the electrolytic bath, and applying a current to the electrolytic bath to perform an electrolysis process. do.

The heating may have a temperature of 1000 to 1100 °C.

According to the present invention, in the aluminum-scandium master alloy electrolytic recovery process, the recovery rate and reaction efficiency of the aluminum-scandium alloy are improved by preventing the problem that the recovery rate of the aluminum-scandium mother alloy is lowered due to the presence of molten aluminum in the electrolyte in the form of droplets. has an enhancing effect.

1 is a diagram schematically showing a cross section of a conventional electrolytic cell for electrolytically depositing an aluminum alloy.
2 to 4 are perspective views showing an anode for electrolysis according to an embodiment of the present invention.
5 is a view schematically showing a cross section of an electrolytic cell according to an embodiment of the present invention.
6 is a graph showing the results of analysis using X-ray diffraction (XRD) of the metal produced on the surface of the cathode of the electrolytic cell in Example.
7 is a photograph of a solidified aluminum droplet produced by solidifying a molten aluminum droplet in a comparative example.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention may be modified in various forms, and the scope of the present invention is not limited to the embodiments described below.

The present invention relates to an electrolytic anode for electrolysis of an aluminum-scandium mother alloy, an electrolytic bath including the same, and an electrolysis method using the electrolytic bath.

2 to 4 are perspective views showing an anode for electrolysis according to an embodiment of the present invention.

In the anode 10 for electrolysis according to an embodiment of the present invention, in an anode included in an electrolytic cell for electrolysis of an aluminum-scandium mother alloy, a concave portion is formed at an end of the anode, and a by-product gas ( An outlet 20 for discharging 60 to the outside may be formed.

In general, since an electrolysis process for recovering an aluminum-scandium alloy is performed at a high temperature of 700° C. or more, the electrolyte 70 and the aluminum cathode 40 included in the electrolysis bath are in a molten state. The density difference between the molten electrolyte and the molten aluminum is not large, and the flow of the molten aluminum cathode is caused by carbon dioxide, which is a by-product gas 60 generated from the anode 10 during the electrolytic reaction. Due to this, a part of the molten aluminum is mixed into the electrolyte to generate aluminum droplets 50, and since the aluminum droplets cannot function as a cathode, they cannot participate in the electrolysis reaction, resulting in a problem in that the reaction efficiency of the electrolysis process is lowered. .

In addition, when the aluminum droplet 50 rises and is positioned on the surface of the electrolyte 70, it reacts with oxygen in the air to produce aluminum oxide (Al ₂ O ₃ ), so it cannot participate in the reaction any longer. Therefore, there is a problem in that the recovery rate and reaction efficiency of the aluminum-scandium alloy are very low because the content of the aluminum anode 40 is reduced.

However, the anode 10 for electrolysis according to an embodiment of the present invention effectively separates the aluminum droplets 50 so that they can be reused as a cathode, thereby increasing the recovery rate and reaction efficiency of the aluminum-scandium alloy.

First, since a concave portion is formed at the end of the anode 10 for electrolysis, the reaction area is remarkably increased compared to the end of the conventional flat anode, resulting in an effect of increasing reaction efficiency.

In addition, since the concave portion is formed at the end of the anode 10 for electrolysis, a plurality of aluminum droplets 50 floating around the end of the anode can be collected. When a plurality of aluminum droplets are gathered at the end, they may merge with each other and increase in size to a certain size or more. As a result, the increased aluminum droplets may settle downward due to their weight. Therefore, the aluminum droplet is mixed into the aluminum cathode 40 present at the bottom of the electrolytic cell and operates as a cathode, thereby improving the recovery rate and reaction efficiency of the aluminum-scandium alloy.

Furthermore, the concave portion collects the molten aluminum droplets 50 around the end of the anode, thereby preventing the aluminum droplets from floating, thereby preventing aluminum oxide from being generated.

An outlet 20 may be formed in the concave portion of the anode 10 for electrolysis according to an embodiment of the present invention, and by-product gas 60 accumulated in the concave portion of the anode may be discharged to the outside through the outlet. there is. Due to this, there is an effect of reducing the degree to which the electrolyte 70 flows due to the by-product gas, and consequently, the degree to which the aluminum anode 40 is mixed into the electrolyte to form the aluminum droplet 50.

The concave portion may have any one shape selected from the group consisting of a cone, an elliptical cone, a polygonal pyramid, a truncated cone, an elliptical truncated cone, a polygonal truncated cone, a cylinder, an elliptical cylinder, a polygonal cylinder, a hemisphere, and a semi-ellipsoid. In FIG. 2, the concave portion of the anode has a triangular pyramid shape, in FIG. 3, the concave portion of the anode has a cylindrical shape, and in FIG. 4, the concave portion of the anode has a semi-ellipsoidal shape.

When the concave portion has a truncated cone shape, an elliptical truncated shape, a polygonal truncated shape, a cylinder shape, or an elliptical columnar shape, it is difficult for the by-product gas 60 to be discharged to the outside through the outlet 20 due to accumulation at the corner of each shape. The concave portion is preferably in the shape of a cone, an elliptical cone, a polygonal cone, a hemisphere or a semi-ellipsoid.

Two or more outlets 20 may be formed in the concave portion. Since the plurality of outlets are formed in the concave portion, the by-product gas 60 generated inside the electrolytic cell can be quickly discharged out of the electrolytic cell, thereby preventing the formation of aluminum droplets. On the other hand, if the number of the concave portions is too large, the activity of the positive electrode may deteriorate. Therefore, it is preferable that 10 or less outlets are formed in the concave portion.

The location where the outlet 20 is formed in the concave portion is not particularly limited, but is preferably formed in the center of the concave portion. When the outlet is formed at the end of the concave portion, only a portion of the by-product gas 60 collected in the concave portion is discharged, and aluminum droplets may be formed due to the remaining by-product gas. Therefore, the outlet is preferably formed in the center of the concave portion. do.

Meanwhile, the outlet 20 preferably has a maximum diameter of 1 mm or less. If the maximum diameter exceeds 1 mm, the aluminum droplet 50 may block the outlet. On the other hand, the lower limit of the diameter of the outlet is not particularly limited, but is preferably 10 μm or more so that the by-product gas 60 is easily discharged.

According to another embodiment of the present invention, it is possible to provide an electrolytic cell including the anode 10 for electrolysis. 5 is a view schematically showing a cross section of an electrolytic cell according to an embodiment of the present invention.

The electrolytic bath may include an electrolytic bath body 30 filled with electrolyte 70, an aluminum cathode 40 disposed on the bottom of the electrolytic bath, and the anode 10 for electrolysis. Since the electrolysis process performed in the electrolytic bath is performed at a high temperature of 700° C. or higher, the electrolyte and the aluminum cathode included in the electrolytic bath may be in a molten state.

As the electrolysis process progresses, in the anode 10 for electrolysis, an oxidation reaction proceeds in the electrolyte solution to generate by-product gas 60 such as chlorine gas, fluorine gas, carbon dioxide or carbon monoxide. Meanwhile, scandium oxide is supplied to the electrolytic cell body 30, and the scandium oxide undergoes a reduction reaction at the interface between molten aluminum, which is a negative electrode, and the electrolyte 70, thereby producing an aluminum-scamdium alloy.

The electrolyte 70 is not particularly limited as long as it is generally used in an electrolytic cell for electrolytically depositing an aluminum-scandium alloy, but may be, for example, fluoride, chloride, or a mixture thereof.

The fluoride is sodium hexafluoroaluminate (Na ₃ AlF ₆ ), potassium hexafluoroaluminate (K ₃ AlF ₆ ), aluminum fluoride (AlF ₃ ), calcium fluoride (CaF ₂ ), sodium fluoride (NaF ), potassium fluoride (KF), potassium bromine fluoride (KBrF ₄ ), potassium hydrogen fluoride (KHF ₂ ), calcium hexafluorophosphate (KPF ₆ ), potassium hexafluorosilicate (K ₂ SiF ₆ ), It may be at least one selected from the group consisting of lithium hexafluoroaluminate (Li ₃ AlF ₆ ), ammonium hexafluoroaluminate ((NH ₄ ) ₃ AlF ₆ ), and potassium fluorophosphate (KPO ₂ F ₂ ). Meanwhile, the chloride may be at least one selected from the group consisting of lithium chloride (LiCl), potassium chloride (KCl), chromium chloride (CrCl ₂ ), calcium chloride (CaCl ₂ ), and bromine chloride (BrCl).

The present invention can provide an electrolysis method for electrolyzing an aluminum-scandium alloy using the electrolytic cell.

An electrolytic method according to an embodiment of the present invention includes supplying scandium oxide and an electrolyte 70 to the electrolytic bath, heating the electrolytic bath, and applying a current to the electrolytic bath to perform an electrolysis process. can do.

Specifically, the electrolysis process may be performed by supplying scandium oxide and the electrolyte 70 to the electrolytic bath, heating the scandium oxide and the electrolyte, and applying current to the cathode and anode 10 included in the electrolysis bath. Through this electrolysis method, in the anode, chlorine ions or fluorine ions in the electrolyte may be oxidized to generate by-product gases 60 such as chlorine gas, fluorine gas, carbon dioxide, and carbon monoxide. Meanwhile, the scandium oxide supplied to the electrolytic cell may be reduced at the interface between molten aluminum, which is a negative electrode, and the electrolyte to form an aluminum-scandium alloy.

In the heating step, heating is preferably performed in a temperature range of 900 to 1300 ° C. If the heating temperature is less than 900 ° C, it is difficult to perform the electrolysis process because the salt does not melt, and if it exceeds 1300 ° C, it is difficult to operate the high-temperature electrolysis process. It is uneconomical due to increased energy costs for

Meanwhile, in the step of applying current to the cathode and anode 10 to perform the electrolysis process, the current applied to the cathode and anode is preferably -1.0 to -2.0A. If the applied current is less than -1.0A or exceeds -2.0A, the reduction reaction of the aluminum-scandium alloy does not occur in the electrolytic bath, and the recovery rate of the alloy may be reduced.

Hereinafter, the present invention will be described in more detail through specific examples. The following examples are merely examples to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

An electrolytic cell body 30 filled with sodium fluoride, aluminum fluoride, and calcium fluoride as electrolyte 70, a carbon anode 10 impregnated with the electrolyte, and an aluminum cathode 40 disposed on the bottom of the electrolytic cell body. An electrolytic cell was prepared, and scandium oxide was supplied to the electrolytic cell body. A conical concave portion is formed at an end of the carbon anode, and an outlet 20 is formed in the center of the concave portion. After heating the scandium oxide and the electrolyte included in the electrolytic cell body to 1000 ° C, an electrolysis process was performed by applying a current of -1.5 A to the cathode and anode.

The density of molten aluminum is 2.975 g/m ³ and the weight is 80 g. Meanwhile, the electrolyte 70 is 38% by weight of sodium fluoride, 26% by weight of aluminum fluoride, and 36% by weight of calcium fluoride, and has a density of 2.12 g/m ³ . After the electrolytic process, the recovered aluminum-scandium alloy weighed 79.3 g, the recovery rate was 99%, and almost no solidified aluminum droplets were found. 6 is a graph showing the results of analysis using X-ray diffraction (XRD) of metal generated on the surface of the cathode, and it was confirmed that the aluminum-scandium alloy was prepared.

comparative example

An electrolytic cell body 30 filled with sodium fluoride, aluminum fluoride, and calcium fluoride as electrolyte 70, a cylindrical carbon anode 10 impregnated with the electrolyte, and an aluminum cathode 40 disposed on the bottom of the electrolytic cell body A containing electrolytic cell was prepared, and scandium oxide was supplied to the electrolytic cell body. After heating the scandium oxide and the electrolyte included in the electrolytic cell body to 1000 ° C, an electrolysis process was performed by applying a current of -1.5 A to the cathode and anode.

The density of molten aluminum is 2.975 g/m ³ and the weight is 80 g. Meanwhile, the electrolyte 70 is 38% by weight of sodium fluoride, 26% by weight of aluminum fluoride, and 36% by weight of calcium fluoride, and has a density of 2.12 g/m ³ . After the electrolytic process, the recovered aluminum-scandium alloy weighs 50 g, and the recovery rate is very low at 62%. In addition, solidified aluminum droplets produced by solidification of the molten aluminum droplet 50 have been found. 7 is a photograph of the solidified aluminum droplet, confirming that the diameter is approximately 3 to 8 mm.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and variations are possible without departing from the technical spirit of the present invention described in the claims. It will be obvious to those skilled in the art.

10: anode
20: outlet
30: Electrolyzer body
40: aluminum cathode
50: aluminum droplet
60: by-product gas
70: electrolyte

Claims (10)

In the electrolytic bath for electrolysis of the aluminum-scandium mother alloy,
an electrolytic anode having a concave portion formed at an end thereof and a discharge port for discharging by-product gas to the outside in the concave portion;
Electrolyzer body filled with electrolyte; and
An electrolytic cell comprising an aluminum cathode disposed at the bottom of the electrolytic cell.
According to claim 1,
The concave part,
Conical, elliptical, polygonal, truncated, truncated, truncated, polygonal, cylinder, elliptical, polygonal, hemispherical, or semi-ellipsoid electrolyzer.
According to claim 1,
The concave portion is an electrolytic cell in which two or more outlets are formed.
According to claim 1,
The outlet is an electrolytic cell formed in the center of the concave portion.
According to claim 1,
The outlet has a maximum diameter of 1 mm or less.
delete delete According to claim 1,
The electrolyte is fluoride, chloride or a mixture thereof.
supplying scandium oxide and an electrolyte to the electrolytic cell of any one of claims 1 to 5 and 8;
heating the electrolyzer; and
An electrolysis method comprising the step of applying a current to the electrolysis cell to perform an electrolysis process.
According to claim 9,
The heating is an electrolysis method in which the temperature is 1000 to 1100 ° C.

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