KR102538237B1 - Process for recovering neodymium and apparatus for recovering neodymium - Google Patents

Abstract

The present invention relates to a neodymium recovery process and a neodymium recovery device. One aspect of the present invention includes the steps of selectively ionizing neodymium by introducing a neodymium magnet into a molten chloride salt; electrolytically refining the neodymium-ionized molten salt using a liquid cadmium electrode; recovering the neodymium-cadmium alloy formed through the electrolytic refining; and recovering neodymium by fractional distillation of the recovered neodymium-cadmium alloy.

Description

Neodymium recovery process and neodymium recovery device {PROCESS FOR RECOVERING NEODYMIUM AND APPARATUS FOR RECOVERING NEODYMIUM}

The present invention relates to a neodymium recovery process and a neodymium recovery device.

A neodymium magnet is a type of permanent magnet that is currently most widely used. Neodymium in a neodymium magnet strongly fixes the direction of magnetization of iron and can maintain strong magnetism. Due to these characteristics, neodymium magnets are used in various fields such as electronic devices, generators, and electric vehicles, and account for more than 50% of magnets used for industrial purposes. In addition, the use of neodymium magnets is expected to continue to increase according to global trends such as the increase in the spread of electronic devices, the expansion of the use of renewable energy, and the increase in the spread of electric vehicles.

On the other hand, more than 85% of the world's production of neodymium, a major element constituting neodymium magnets, is made in China, and it is a material that is mainly managed in terms of resource security. In general, the durability of neodymium magnets is less than 20 years, and the rate of recovering neodymium from waste neodymium magnets is less than 6%, and it is predicted that it will not exceed 10% even within the next 10 years. Therefore, it is inevitable to develop a process for efficiently recovering neodymium from neodymium magnets.

Currently, processes for recovering neodymium from neodymium magnets are divided into a hydrometallurgical process and a pyrometallurgical process.

Among them, the hydrochemical process has a problem in that a large amount of by-products such as high-temperature Cl ₂ and SO ₂ /SO ₃ are generated during electrolytic refining after dissolving rare earth metals. In addition, the high-temperature process is divided into high-temperature melting, extraction using liquid magnesium, and electrolytic smelting using molten salt. High-temperature melting and extraction using liquid magnesium require high-temperature conditions of 800 ° C to 1300 ° C, and in particular, using liquid magnesium In the case of extraction, difficulties exist due to the high reactivity of liquid magnesium.

For this reason, molten chloride-based neodymium extraction, which can be electrolytically smelted at a relatively low temperature, is attracting attention.

However, non-reactive solid electrodes, which are mainly used in molten chloride-based neodymium extraction, extract reduced neodymium in powder form due to the disproportionation-inverse disproportionation reaction (2Nd ³⁺ + Nd(s) ↔ 3Nd ²⁺ ) of neodymium. It has the disadvantage of being difficult to separate and refine. In addition, the reverse disproportionation reaction of neodymium results in a decrease in power efficiency.

Therefore, it is necessary to develop a method for recovering neodymium capable of efficiently suppressing the reverse disproportionation reaction of neodymium.

The above background art 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 art disclosed to the general public prior to the present application.
[Prior art literature]
[Non-Patent Literature]
Zhongsheng et al., ACS Sustainable Chemistry & Engineering, Vol.2, pp. 2536-2543 (2014.10.06.)

The present invention is to solve the above problems, and an object of the present invention is to provide a neodymium recovery process capable of recovering high-purity neodymium from a neodymium magnet by suppressing the reverse disproportionation reaction of neodymium and a neodymium recovery device therefor. is to do

However, the problem to be solved by the present invention is 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 the steps of selectively ionizing neodymium by introducing a neodymium magnet into a molten chloride salt; electrolytically refining the neodymium-ionized molten salt using a liquid cadmium electrode; recovering the neodymium-cadmium alloy formed through the electrolytic refining; and recovering neodymium by fractional distillation of the recovered neodymium-cadmium alloy.

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

According to one embodiment, the chloride molten salt may contain 0.1 wt% to 10 wt% of CdCl ₂ .

According to one embodiment, the step of selectively ionizing neodymium may be performed at a temperature of 400 °C to 600 °C.

According to one embodiment, selectively ionizing the neodymium; Thereafter, measuring the concentration of cadmium ions contained in the chloride molten salt through a cyclic current method; may further include.

According to one embodiment, selectively ionizing the neodymium; Thereafter, recovering iron (Fe) contained in the chloride molten salt; may further include.

According to one embodiment, the electrorefining is performed by applying a voltage of -2.0 V to -3.0 V versus the Cl ₂ /Cl ^- reference electrode, or applying a voltage of -1.0 V to -2.0 V versus the Ag/AgCl reference electrode. It may be performed with authorization.

According to one embodiment, the electrorefining may be performed at a temperature of 400 °C to 600 °C for 10 hours to 20 hours.

According to one embodiment, the neodymium-cadmium alloy may include Cd ₁₁ Nd.

According to one embodiment, the fractional distillation may be performed at a pressure of 1 Torr to 10 Torr and a temperature of 700 °C to 2,000 °C.

According to one embodiment, cadmium may be evaporated through the fractional distillation and neodymium in a solid state may be recovered.

According to one embodiment, the purity of the recovered neodymium may be 98% or higher.

Another aspect of the present invention is an ionizer for obtaining neodymium ionized molten salt by introducing a neodymium magnet into chloride molten salt; an electrolytic refining device for electrolytically refining the neodymium-ionized molten salt to obtain a neodymium alloy; and a fractional distillation apparatus for recovering neodymium by fractional distillation of the neodymium alloy.

According to one embodiment, the electrolytic refining device includes a reactor for receiving molten salt in which neodymium (Nd) is ionized; a liquid metal electrode accommodating part located at the bottom of the inside of the reactor; a working electrode connected to the liquid metal electrode; and a reference electrode located inside the reactor and not in contact with the liquid metal electrode accommodating part.

According to an embodiment, a neodymium alloy formed by electrolytic refining may be positioned at a lower end of the liquid metal electrode accommodating part to suppress a reaction with neodymium ions included in the molten salt.

The neodymium recovery process according to the present invention can effectively suppress the disproportionation reaction of neodymium by forming a neodymium-cadmium alloy through electrolytic refining using a liquid cadmium electrode, and recovering neodymium by fractional distillation of the neodymium-cadmium alloy to obtain high purity of neodymium can be obtained.

In addition, the neodymium recovery process according to the present invention can selectively recover neodymium from waste neodymium magnets and recover residual iron, so that more than 99% of waste neodymium magnets can be recycled.

1 is a conceptual diagram of a neodymium recovery process according to an embodiment of the present invention.

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

Terms used in the examples are used only for descriptive purposes and should not be construed as limiting. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the embodiment belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in the present application, they should not be interpreted in an ideal or excessively formal meaning. don't

In addition, in the description with reference to the accompanying drawings, the same reference numerals are given to the same components regardless of reference numerals, and overlapping descriptions thereof will be omitted. In describing the embodiment, if it is determined that a detailed description of a related known technology may unnecessarily obscure the gist of the embodiment, the detailed description will be omitted.

In addition, 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, order, or order of the corresponding component is not limited by the term. When an element is described as being “connected,” “coupled to,” or “connected” to another element, that element may be directly connected or connected to the other element, but there may be another element between the elements. It should be understood that may be "connected", "coupled" or "connected".

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

One aspect of the present invention includes the steps of selectively ionizing neodymium by introducing a neodymium magnet into a molten chloride salt; electrolytically refining the neodymium-ionized molten salt using a liquid cadmium electrode; recovering the neodymium-cadmium alloy formed through the electrolytic refining; and recovering neodymium by fractional distillation of the recovered neodymium-cadmium alloy.

The neodymium recovery process according to the present invention can effectively suppress the disproportionation reaction of neodymium and has the effect of obtaining high-purity neodymium.

Hereinafter, the neodymium recovery and fixation according to the present invention will be described in detail step by step.

Steps for Selective Ionization of Neodymium

The first step of the neodymium recovery process according to the present invention is a step of selectively ionizing neodymium in the magnet by introducing the neodymium magnet into the molten chloride salt.

According to one embodiment, the neodymium magnet may be a waste neodymium magnet (Nd ₂ Fe ₁₄ B).

The neodymium recovery process according to the present invention can be used to selectively recover and effectively recycle neodymium contained in waste neodymium magnets.

In addition, by incidentally recovering residual iron (Fe) contained in waste neodymium magnets (Nd ₂ Fe ₁₄ B), more than 99% of neodymium magnets can be recycled.

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

According to one embodiment, the chloride molten salt may include a eutectic salt.

According to one embodiment, the chloride molten salt may contain 0.1 wt% to 10 wt% of CdCl ₂ .

Preferably, the chloride molten salt may contain 2.5% to 10% by weight of CdCl ₂ .

If the content of CdCl ₂ included in the chloride molten salt is less than the above range, neodymium may not be sufficiently ionized, and if it exceeds the above range, the eutectic of the eutectic salt used as the basic salt is destroyed, and work is performed. sexuality may deteriorate.

Meanwhile, the amount of neodymium that can be extracted per 1 g of CdCl ₂ is 0.5246 g. Therefore, the weight ratio of CdCl ₂ and neodymium in the magnet is preferably 1:0.6 to 1:0.95.

If the content of CdCl ₂ exceeds the above range based on the content of neodymium in the magnet, the remaining CdCl ₂ increases and a lot of electricity is consumed to recover Cd ²⁺ in the electrolytic refining step. can happen

On the other hand, based on the content of neodymium in the magnet, when the content of CdCl ₂ is less than the above range, disproportionation between Nd ³⁺ ions present in the Nd metal and salt (3Nd ²⁺ → Nd + 2Nd ³⁺ )-reverse Neodymium haze may be generated due to the disproportionation (Nd + 2Nd ³⁺ → 3Nd ²⁺ ) reaction, which may reduce process efficiency.

That is, the ΔG value of the reaction is very low at -20.8±3.2 kJ/mol, and a reverse disproportionation reaction occurs near a neodymium magnet (NdFeB) with Nd and a disproportionation reaction occurs in the bulk region, resulting in neodymium ash (Nd ash) is formed to generate neodymium haze (Nd haze), and the haze cannot be electrically reduced to Cd in the electrolytic refining process, causing a decrease in efficiency.

The chloride molten salt may selectively ionize neodymium included in the neodymium magnet by including CdCl ₂ .

This is because neodymium is more reactive (ionization tendency) than cadmium, and neodymium selectively causes an oxidation reaction.

Specifically, the redox potential of cadmium (vs. Cl ₂ /Cl ^- ) in the LiCl-KCl molten salt at 500 °C is -1.532 V, which is between neodymium (-3.078 V) and iron (-1.388 V), and CdCl When using ₂ , only neodymium can be selectively oxidized. At this time, iron does not react and remains.

Since the neodymium contained in the neodymium magnet reacts vigorously with cadmium in the chloride molten salt and is easily ionized, all of the neodymium contained in the neodymium magnet can be converted into ions when sufficient cadmium ions are present in the chloride molten salt. there is.

According to one embodiment, the step of selectively ionizing neodymium may be performed at a temperature of 400 °C to 600 °C.

If the step of selectively ionizing neodymium is performed at a temperature below the above range, the rate at which neodymium is dissolved from the neodymium magnet may decrease, and when the step of selectively ionizing neodymium is performed at a temperature above the above range, a high temperature environment is required. Accordingly, the process design burden may increase.

According to one embodiment, selectively ionizing the neodymium; Thereafter, measuring the concentration of cadmium ions contained in the chloride molten salt through a cyclic current method; may further include.

In the neodymium recovery process according to the present invention, even if neodymium and cadmium ions coexist in the chloride molten salt, the concentration of cadmium ions can be independently measured through a cyclic current method, and the amount of ionized neodymium can be inversely calculated.

Since the redox potential of neodymium is much more negative than the redox potential of cadmium in the chloride molten salt, the concentration of cadmium ions can be independently observed with respect to the cyclic amperometry. In addition, even after neodymium in the neodymium magnet reacts with cadmium present in the molten salt, cadmium ions show independent behavior.

According to one embodiment, the cyclic amperometry may be performed in the range of -2.235 V to -0.735 V (vs. Cl ₂ /Cl ^- ) or -1.0 V to +0.5 V (vs. 1 wt % Ag/AgCl). can

According to one embodiment, selectively ionizing the neodymium; Thereafter, recovering iron (Fe) contained in the chloride molten salt; may further include.

Since iron contained in the rare earth magnet cannot be ionized by cadmium in the molten salt, iron may be physically recovered using a porous basket or the like.

Electrorefining step and recovery step of neodymium-cadmium alloy

The next step is electrolytically refining the molten salt in which the neodymium is ionized using a liquid cadmium electrode.

At this time, the liquid cadmium electrode may be a cathode electrode.

Through the electrolytic refining step, a neodymium-cadmium alloy is formed, and the activity of neodymium is reduced. Also, since the density of the formed neodymium-cadmium alloy is higher than that of liquid cadmium, the formed neodymium-cadmium alloy is positioned lower than that of liquid cadmium.

For example, the density of LiCl-KCl-NdCl ₃ (aq) is 1.62 g/cm ³ , the density of Cd(l) is 7.75 g/cm ³ , and the density of Cd ₁₁ Nd(s) is 8.57 g/cm ³ , When the above three materials are mixed, neodymium-cadmium sinks to the bottom and contact between LiCl-KCl-NdCl ₃ (aq) and Cd ₁₁ Nd(s) is blocked due to the density difference. Thus, neodymium in the neodymium-cadmium alloy is inhibited from reacting with neodymium in the molten salt.

That is, the neodymium-cadmium alloy is protected from the molten salt, and the reaction between neodymium contained in the neodymium-cadmium alloy and neodymium ions contained in the molten salt is suppressed, and through this, the reverse disproportionation reaction of neodymium, which was a problem in the prior art, (2Nd ³⁺ + Nd(s) → 3Nd ²⁺ ) can be suppressed effectively.

On the other hand, when neodymium metal is added to LiCl-KCl-NdCl ₃ (aq), a disproportionation reaction occurs. The disproportionation reaction of neodymium is difficult to separate and purify as the reduced neodymium is extracted in powder form, There is a problem of lowering power efficiency in the molten salt-based recovery process itself.

According to one embodiment, the electrorefining is performed by applying a voltage of -2.0 V to -3.0 V versus the Cl ₂ /Cl ^- reference electrode, or applying a voltage of -1.0 V to -2.0 V versus the Ag/AgCl reference electrode. It may be performed with authorization.

Preferably, the electrolytic refining is performed by applying a voltage of -2.3 V to -2.7 V versus a Cl ₂ /Cl ^-reference electrode, or a voltage of -1.0 V to -1.5 V versus a 1 wt % Ag/AgCl reference electrode. It may be performed by authorizing.

The voltage condition may be an optimal condition range capable of forming a Cd ₁₁ Nd alloy through electrolytic refining.

According to one embodiment, the neodymium-cadmium alloy may include Cd ₁₁ Nd.

According to one embodiment, the electrorefining may be performed at a temperature of 400 °C to 600 °C for 10 hours to 20 hours.

According to one embodiment, in the electrorefining step, an electric charge amount of 100 C/g-Cd to 180 C/g-Cd may be applied.

That is, an electric charge of 100 C to 180 C per 1 g of liquid cadmium of the liquid cadmium electrode may be applied.

If the applied charge amount is less than the above range, the recovery amount of neodymium may be low, and when the applied charge amount exceeds the above range, the amount of electrodeposited lithium (Li) may be increased and the recovery efficiency may be lowered.

In the neodymium recovery process according to the present invention, even if the electrolytic refining step is performed for 12 hours, the neodymium disproportionation reaction does not occur. Therefore, a neodymium-cadmium alloy can be sufficiently formed through the electrolytic refining step.

fractional distillation step

According to one embodiment, the fractional distillation may be performed at a pressure of 1 Torr to 10 Torr and a temperature of 700 °C to 2,000 °C.

Preferably, the fractional distillation may be performed at a pressure of 1.2 Torr to 3.0 Torr, more preferably, at a pressure of 1.2 Torr to 1.6 Torr.

The neodymium recovery process according to the present invention has the advantage of being able to be performed under relatively low pressure conditions.

According to one embodiment, the fractional distillation is carried out at a temperature of 700 ° C to 2,000 ° C, preferably at a temperature of 800 ° C to 1,500 ° C, more preferably at a temperature of 800 ° C to 1,200 ° C, even more preferably Preferably, it may be performed at a temperature of 900 ° C to 1,000 ° C.

Cadmium has a very high vapor pressure compared to neodymium, so it can be classified easily in this temperature range.

Cadmium has a melting point of 321 °C and a boiling point of 767 °C, while neodymium has a melting point of 1,024 °C and a boiling point of 3,074 °C. Therefore, cadmium can be evaporated and neodymium can be effectively recovered in the above temperature range. In addition, neodymium in a solid state can be recovered when carried out at 1,000 ° C or less.

According to one embodiment, the fractional distillation may be performed for 10 to 15 hours at a temperature of 600 °C to 1,000 °C and a pressure of 0.001 to 0.003 atm.

According to one embodiment, cadmium may be evaporated through the fractional distillation and neodymium in a solid state may be recovered.

In the neodymium recovery process according to the present invention, by fractional distillation in the above temperature range, cadmium can be evaporated and neodymium can be recovered in a solid state.

Neodymium in a solid state is easy to recover, so the recovery rate of neodymium can be increased.

According to one embodiment, the purity of the recovered neodymium may be 98% or higher.

The neodymium recovery process according to the present invention has the advantage of being able to recover, in particular, high-purity neodymium of 98% or more.

According to one embodiment, cadmium evaporated through the fractional distillation may be separately recovered.

Neodymium recovery device

Another aspect of the present invention is an ionizer for obtaining neodymium ionized molten salt by introducing a neodymium magnet into chloride molten salt; an electrolytic refining device for electrolytically refining the neodymium-ionized molten salt to obtain a neodymium alloy; and a fractional distillation apparatus for recovering neodymium by fractional distillation of the neodymium alloy.

According to one embodiment, the electrolytic refining device includes a reactor for receiving molten salt in which neodymium (Nd) is ionized; a liquid metal electrode accommodating part located at the bottom of the inside of the reactor; a working electrode connected to the liquid metal electrode; and a reference electrode located inside the reactor and not in contact with the liquid metal electrode accommodating part.

According to an embodiment, a neodymium alloy formed by electrolytic refining may be positioned at a lower end of the liquid metal electrode accommodating part to suppress a reaction with neodymium ions included in the molten salt.

According to one embodiment, a neodymium collection device connected to the fractional distillation device; may further include.

Hereinafter, the present invention will be described in more detail by 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> Recovery process of neodymium from neodymium magnet

1) Selective ionization step of neodymium

A neodymium magnet (Nd ₂ Fe ₁₄ B) was added to LiCl-KCl-2.5% by weight molten salt at a temperature of 500 °C and reacted.

Neodymium contained in the neodymium magnet reacted very vigorously with cadmium ions in the molten salt, and all reactions were completed within 2 hours.

2) Electrolytic refining step and recovery step of neodymium-cadmium alloy

Neodymium ionized molten salt was electrolytically refined using a liquid cadmium cathode. Electrolytic refining was performed for 12 hours at a temperature of 500 °C by applying a voltage of -1.5 V (vs. 1 wt% Ag/AgCl). A neodymium-cadmium alloy formed through electrolytic refining was recovered.

3) fractional distillation step

18 g of the recovered neodymium-cadmium alloy (Cd ₁₁ Nd) was distilled in a low pressure and high temperature environment (1.6 Torr, 1,000 °C).

After volatilizing cadmium, neodymium with a purity of 98% or more and a cadmium content of less than 2% was recovered.

1 is a conceptual diagram of a neodymium recovery process according to an embodiment of the present invention.

Referring to FIG. 1, the neodymium recovery process according to the present invention includes a selective ionization process of neodymium in a neodymium magnet, a recovery process of neodymium-cadmium alloy through electrolytic refining based on a liquid cadmium electrode, and a recovery process of high purity neodymium through fractional distillation. You can check the progress in order.

<Experimental Example 1> Confirmation of selective ionization effect of neodymium using chloride molten salt

LiCl-KCl-n wt% CdCl ₂ (n: 0.1 ~ 2.5) molten salt in a 500 ℃ environment in a glove box controlled so that the H ₂ OO ₂ fraction is less than 0.1 ppm. Cathodic peak data of cadmium through cyclic amperometry. It was confirmed that (voltage, current density) showed a constant behavior according to the concentration.

In addition, for LiCl-KCl-n wt% CdCl ₂ -m wt% NdCl ₃ (n: 0 to 1.9, m: 2.0 to 0.1) molten salt, the redox potential of neodymium (-3.078 V vs. C _l2 /Cl ^- ) is much more negative than the redox potential of cadmium (-1.532 V vs. Cl ₂ /Cl ^- ), -2.235 V ~ -0.735 V (vs. Cl ₂ /Cl ^- ) or -1.0 V ~ +0.5 V (vs. It was confirmed that cadmium exhibited independent behavior in the cyclic amperometry in the range of 1 wt% Ag/AgCl).

On the other hand, neodymium metal and neodymium in the neodymium magnet reacted very vigorously with cadmium ions in the molten salt and all reacted within 2 hours, and it was confirmed that the cathodic peak of CdCl ₂ behaved independently even after the reaction was over. In addition, by analyzing the composition of the salt by ICP-OES, it was confirmed that the composition of iron was very low and did not react.

From these results, it can be seen that neodymium metal and neodymium contained in neodymium magnets are easily ionized as cadmium ions in molten salt, and that all neodymium metal can be converted into neodymium ions if the amount of cadmium ions is sufficient. It was found that the iron in the magnet could not be ionized by cadmium, so the iron residue after the reaction could be physically recovered using a porous basket.

In addition, even if neodymium-cadmium ions coexist in the molten salt, the concentration of cadmium ions can be independently observed through a cyclic current method, and it is found that the amount of ionized neodymium can be inversely calculated from this.

<Experimental Example 2> Confirmation of neodymium disproportionation inhibitory effect during electrolytic refining using a liquid cadmium electrode

Cyclometry was performed on two molten salts (LiCl-KCl, DODOR) using a liquid cadmium electrode. Assuming that there is no significant difference in the activities of the two salts LiCl-KCl, the electrochemical behavior of 1 wt% NdCl ₃ was evaluated.

From this, it was confirmed that the potential to form Cd ₁₁ Nd, which is the most cadmium-rich alloy among neodymium-cadmium alloys, is about -2.5 V (vs Cl ₂ /Cl ^- ) or -1.25 V (vs. 1 wt% Ag/AgCl). , Based on this, electrolytic recovery was performed at -2.75 V (vs Cl ₂ /Cl ^- ) or -1.5 V (vs. 1 wt % Ag/AgCl) voltage. After completion of the electrolytic recovery, the composition was analyzed through SEM-EDS, and it was confirmed that Cd ₁₁ Nd was formed.

When neodymium metal is added to the LiCl-KCl-NdCl ₃ molten salt, it can be observed that the open circuit potential for the inert solid cathode becomes negative due to the disproportionation reaction, which is This is the simplest way to confirm that an inverse disproportionation reaction occurs.

It was confirmed that the open circuit potential was constant even when the neodymium-cadmium alloy formed through the electrolytic recovery was put into the LiCl-KCl-NdCl ₃ molten salt and left for 12 hours, which is because the reverse disproportionation reaction of neodymium did not occur. am.

This can be explained by the difference in Gibbs free energy, and as confirmed in the SEM-EDS, the density of the neodymium-cadmium alloy is heavier than pure cadmium and is located at the lower end of the electrode. As a result, neodymium in the alloy is physically This is also because it failed to react with neodymium ions.

From these results, it was confirmed that neodymium can be efficiently recovered by suppressing the reverse disproportionation reaction of neodymium by recovering neodymium in the form of a neodymium-cadmium alloy during electrolytic refining using a liquid cadmium electrode.

<Experimental Example 3> Confirmation of high-purity neodymium recovery effect through fractional distillation of neodymium-cadmium alloy

Additional experiments were conducted to confirm the purity of neodymium recovered from the fractional distillation of neodymium-cadmium alloys.

Prior to the experiment, 0.1319 g of NdFeB magnet was added to 5 g of LiCl-KCl-5 wt% CdCl ₂ molten salt, and after 4 hours, the composition of the salt was checked. Nd 0.59 wt%, Cd 1.37 wt%, Fe 0.0060 wt% , it was found that the environment was almost free of Fe.

Therefore, when inducing co-electrodeposition of Nd-Cd-Li using a liquid cadmium electrode with neodymium, even if LiCl-KCl-NdCl ₃ salt is used instead of NdFeB-CdCl ₂ reactive salt, it is not expected to significantly affect the results of this experiment. It was thought.

In order to confirm the purity of the metal recovered by fractional distillation, a voltage of -1.20 V (vs. 1 wt% Ag/AgCl) was applied to 100 g of Cd in a LiCl-KCl-5 wt% NdCl ₃ environment to obtain Nd and Li was electrodeposited.

0.5 g of the resulting Cd-Nd-Li alloy specimens were randomly extracted to make 10 specimens for composition inspection, and it was confirmed that the average concentrations of the resulting specimens were 90.87% by weight of Cd, 8.75% by weight of Nd, and 0.382% by weight of Li. .

The specimen was put into a vacuum distillation apparatus and distilled at 0.002 atm, 600 ° C and 800 ° C for 12 hours, respectively, and the composition of the remaining specimen is shown in Table 1.

(weight%) CD Nd Li Specimen before experiment 90.87 8.75 0.382 600 ℃, 0.002 atm 43.31 55.90 0.789 800 ℃, 0.002 atm 0.0012 99.99 X 800 ℃, 0.002 atm
Metals recovered by distillation 99.754 0.016 0.240

Referring to Table 1, it can be seen that it is possible to volatilize both Cd and Li and recover pure Nd at 800 °C and 0.002 atmospheric pressure.

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

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

Claims (15)

Injecting neodymium magnets (NdFeB) into chloride molten salt to selectively ionize neodymium;
electrolytically refining the neodymium-ionized molten salt using a liquid cadmium electrode;
recovering the neodymium-cadmium alloy formed through the electrolytic refining; and
recovering neodymium by fractional distillation of the recovered neodymium-cadmium alloy;
including,
The chloride molten salt is LiCl-KCl, NaCl-KCl, CsCl-KCl, LiCl-NaCl-CaCl ₂ -BaCl ₂ , NaCl-KCl-BaCl ₂ , CdF ₂ , NdCl ₃ , CeCl ₃ and LaCl ₃ At least one selected from the group consisting of; and 2.5% to 10% by weight of CdCl ₂ ;
The step of selectively ionizing neodymium is performed at a temperature of 400 ° C to 600 ° C,
The electrolytic refining is performed by applying a voltage of -2.0 V to -3.0 V relative to Cl ₂ /Cl ^- reference electrode,
In the electrolytic refining step, an electric charge of 100 C/g-Cd to 180 C/g-Cd is applied,
The fractional distillation is carried out at a pressure of 1.2 Torr to 1.6 Torr and a temperature of 900 ℃ to 1,000 ℃,
Neodymium recovery process.
delete delete delete According to claim 1,
selectively ionizing the neodymium; Thereafter, electrolytically refining the molten salt in which the neodymium is ionized using a liquid cadmium electrode; Between,
Measuring the concentration of cadmium ions contained in the chloride molten salt through cyclic voltammetry; further comprising,
Neodymium recovery process.
According to claim 1,
selectively ionizing the neodymium; and electrolytically refining the neodymium-ionized molten salt using a liquid cadmium electrode. Between,
Recovering iron (Fe) contained in the neodymium magnet (NdFeB); further comprising,
Neodymium recovery process.
delete According to claim 1,
In the electrolytic refining step,
At a temperature of 400 ℃ to 600 ℃, which is carried out for 10 hours to 20 hours,
Neodymium recovery process.
delete delete According to claim 1,
Evaporation of cadmium through the fractional distillation and recovery of neodymium in a solid state,
Neodymium recovery process.
According to claim 1,
The purity of the mass ratio of the recovered neodymium is 98% or more,
Neodymium recovery process.
An ionizer for obtaining neodymium ionized molten salt by injecting a neodymium magnet into chloride molten salt;
an electrolytic refining device for electrolytically refining the neodymium-ionized molten salt to obtain a neodymium alloy; and
Including, a fractional distillation apparatus for recovering neodymium by fractional distillation of the neodymium alloy;
A neodymium recovery device that processes the neodymium recovery process of claim 1.
According to claim 13,
The electrolytic refining device,
a reactor for accommodating molten salt in which neodymium (Nd) is ionized;
a liquid metal electrode accommodating part located at the bottom of the inside of the reactor;
a working electrode connected to the liquid metal electrode; and
A reference electrode located inside the reactor and not in contact with the liquid metal electrode accommodating portion;
Neodymium recovery device.
According to claim 14,
The neodymium alloy formed by electrolytic refining is located at the lower end of the liquid metal electrode accommodating part to suppress the reaction with neodymium ions contained in the molten salt.
Neodymium recovery device.

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