JP6502182B2 - Method of recovering rare earth element and recovery device of rare earth element - Google Patents

Description

  The present invention relates to a rare earth element recovery method and a rare earth element recovery apparatus.

  Rare metals collectively refer to six platinum group rare metals with high resource value, nine rare metals with national reserves, and 17 rare earths with high distribution (hereinafter referred to as "rare earth elements"). Among the rare metals, the rare earth elements have similar chemical properties within the lanthanoid series cycle, and since they are electrochemically very basic element groups, they have been accompanied by difficulties in mutual separation and metal refining. In recent years, the Ministry of the Environment, as a research project to promote the formation of a recycling society, based on the Small Household Appliances Recycling Act enacted from April 1, 2013, recycles rare metals from used small electronic devices and waste disposal technology Development has been focused.

  In addition, there is a high demand for rare earth elements as automobile exhaust gas catalysts, high-performance abrasives, and ferromagnetic magnet members, and technology development to recycle useful rare metals without producing secondary waste in the manufacturing process It is regarded as important. From such a trend of the times, a method of using used small electronic devices as a target medium of rare earth element recovery is effective for recycling as a ferromagnetic magnet member. Stabilization of the supply-demand balance over the rare earth elements is an important issue on a national scale, and a method of securing the rare earth elements in the home country as much as possible is desired.

  One of the effective members in used small electronic devices is Voice Coil Motor (VCM) used for driving the magnetic head of Hard Disk Drive (HDD). The VCM comprises a flat magnet, a back yoke, a yoke supporting a space between the yoke and a neodymium-iron-boron (Nd-Fe-B) rare earth magnet. The weight of the rare earth magnet used in the VCM has a certain width depending on the thickness of the HDD. However, the weight corresponding to 1 to 2 g × 2 pieces of VCM for 2.5 inch HDD and 2 to 10 g × 2 pieces of VCM for 3.5 inch HDD is a standard rare earth magnet weight. Further, although the rare earth content in the VCM member largely depends on the age of production, the neodymium content corresponds to about 26.0% on a weight average, and the dysprosium content corresponds to about 1.6%. With regard to a method for recovering rare earth elements from such rare earth magnet members, a recovery method with low environmental impact is desired.

The “rare earth magnet” is a magnet mainly composed of an intermetallic compound of a rare earth metal and iron (Fe) or cobalt (Co) which is a 3d transition metal. As a composition of the rare earth magnet currently put to practical use in Japan,
1. 2-14-1 neodymium-iron-boron system represented by Nd ₂ Fe ₁₄ B 1-5 type samarium-cobalt system represented by SmCo ₅ 3. Samarium-iron-nitride compound system represented by Sm ₂ Fe ₁₇ N ₃ There are four types of magnets of the 1-5 type praseodymium-cobalt system represented by PrCo ₅ .
Among these, neodymium-iron-boron magnets are the most ferromagnetic, and heavy rare earth elements (for example, dysprosium (Dy)) are used as an additive element for increasing the coercive force.

  On the other hand, iron group elements are often contained in the covering material of the rare earth magnet. The term "iron group element" as used herein is a generic term for the three elements of Groups 4, 9, and 10 of the fourth period on the periodic table, ie, iron (Fe), cobalt (Co), and nickel (Ni). It is. These iron group elements are all 3d transition metals, and exhibit ferromagnetism at normal temperature and pressure.

  Several techniques are known as techniques for recovering rare earth elements in the form of metal or ionic species from rare earth magnets as described above. The following is a list of the methods.

First, there is a molten salt electrolysis method in which a rare earth element is recovered in the form of a metal (see Patent Document 1).
The molten salt electrolysis method is a method of electrolytically depositing a compound containing a rare earth element after bringing an inorganic salt such as an alkali metal halide into a molten state at a high temperature. Due to the high electrolytic bath temperature, there is also the advantage that the rare earth oxide can be dissolved directly in the electrolytic bath. In the technique described in Patent Document 1, during molten salt electrolysis, the anode and the cathode are separated by a bipolar electrode type diaphragm made of a rare earth metal alloy to form an anode chamber and a cathode chamber. While supplying a rare earth metal ion to the anode chamber, a voltage is applied between the anode and the cathode to recover the rare earth metal by electrolysis.

  Next, a resource containing a rare earth element is dissolved in a flame retardant / refractory liquid called an ionic liquid, and if necessary, electrophoresis is performed to concentrate the rare earth element, and then the ionic liquid is added to the liquid. On the other hand, there is a method of electrolytically depositing rare earth elements after electrolytic removal of iron group elements (see Patent Document 2).

  The term "ionic liquid" is a generic term for ionic compounds having a melting point of 100 ° C. or less, which is a combination of cationic species and anionic species, and refers to a molten salt which forms a liquid phase at a temperature of 100 ° C. or less. . The vapor pressure of the ionic liquid is very low, and the ionic liquid virtually produces no harmful vapor. Moreover, the ionic liquid exhibits hydrophobicity by properly selecting the anionic species, and the high polarity of the ionic liquid itself enhances the solubility of the nonpolar substance.

  Finally, there is also a method of using a hydrophobic ionic liquid as a rare earth metal extraction medium (see Patent Document 3). This method is a method in which a rare earth element is extracted as an ion species into an organic phase by distribution equilibrium in a state in which an aqueous phase consisting of an aqueous solution containing a rare earth element and an organic phase which is a hydrophobic ionic liquid are separated.

JP, 2009-287119, A JP 2012-87329 A Japanese Patent Application Publication No. 2007-327085

  While techniques for recovering rare earth elements from rare earth magnets are evolving daily, there are still various points to be improved.

  For example, in the molten salt electrolysis method as disclosed in Patent Document 1 or the like, an electrolytic bath based on neodymium fluoride-alkali metal fluoride can be used from a practical viewpoint in order to electrolytically recover neodymium from a rare earth magnet efficiently. It is appropriate. In this case, neodymium fluoride is a high melting point substance, and it is necessary to set the electrolytic bath temperature to a very high temperature of 1000 ° C. or higher. Therefore, it is necessary to design an apparatus in which consideration is given to each step for safety such as an electrolytic apparatus capable of suppressing a corrosion reaction at high temperature.

  In addition, ceramic materials resistant to high temperature corrosion are generally expensive, require equipment cost, and require a large amount of thermal energy as improvements.

  Certainly, the technique described in Patent Document 1 is an excellent method as a means for electrolytically depositing a rare earth alloy. However, the temperature of the electrolytic bath needs to be 500 to 900 ° C., and the electrolytic voltage needs to be up to 20 V, and it is necessary to take into consideration that the thermal energy and the electrolytic energy are large.

  Next, in the technology described in Patent Document 2, a technology using an ionic liquid (for example, a water content of 50 ppm or less) is described. However, transition metal species (especially iron group elements, more specifically iron) coexist with rare earth elements in the ionic liquid when they are directly dissolved without carrying out appropriate deironization treatment in the pretreatment process of VCM. In this case, at the time of final electrolytic deposition of the rare earth metal, the noble metal is also electrochemically reduced inevitably, so iron co-precipitates in the rare earth electrodeposition to recover high quality rare earth metal. It will be difficult to do.

  Although it is possible to electrolytically recover iron in advance, the large amount of iron contained in the rare earth magnet results in a large energy dose in the electrolytic deposition step. Moreover, complication will be brought about in the cooperation process which carries out electrolytic collection of rare earth metals continuously from electrolytic collection of iron group metals. As a result, there are major points to be improved with regard to the economics of the work process.

  Further, in the technique described in Patent Document 2, it is necessary to concentrate the rare earth element according to the concentration of the rare earth in the ionic liquid, and it is necessary to carry out the electrophoresis treatment. The electrophoresis process requires an applied voltage of about 30 to 50 V. As a result, the energy required for the migration process is enormous, and there are major points to be improved with regard to the economics of the work process.

  Finally, in the case of a solvent extraction method which is a technique represented by Patent Document 3 and which uses distribution equilibrium of an aqueous solution and an ionic liquid, the rare earth element is efficiently extracted by using diglycolic anhydride as an extractant. it can. In addition, when the solvent extraction device is configured in multiple stages, it is also possible to concentrate rare earth species. However, in the solvent extraction method, the rare earth species is in the form of an ionic species in any case, and it is necessary to precipitate it into a borate or carbonate in order to convert it to a stable rare earth solid. Furthermore, even when the rare earth species is recovered as a borate or carbonate, in order to convert it to the form of a metal, it is necessary to electrolyze the rare earth salt in an electrolytic bath or to react with the active metal by thermal reduction. That is, when the solvent extraction method is applied alone, the greatest problem is that the rare earth species can not be recovered in the form of metal.

  As described above, the technology for recovering rare earth elements from rare earth magnets has been evolved daily by many engineers, but the above improvements are also becoming clear. If the above improvement points can be overcome, it will lead to establishing a solid method for securing rare earth elements in their own country, and will greatly contribute to industrial development.

  Then, this invention makes it a main purpose to provide the collection | recovery method and rare earth element collection | recovery apparatus of rare earth elements which improve the quality of the rare earth elements collect | recovered, simplifying an operation process.

  The present inventors diligently studied to solve the above problems. In this intensive study, the inventor adopted electrolytic deposition as a method of recovering a rare earth element from a rare earth magnet. And, in the elements contained in the electrolytic bath at the stage of recovery of the rare earth elements by electrolytic deposition, attention is paid to the method that only elements which are electrochemically inferior to the rare earth elements are contained as elements other than the rare earth elements. did. In other words, we focused on the method of creating the situation that makes the electrolytic deposition of the rare earth element most easy.

  Therefore, in order to electrolytically deposit a rare earth element, the present inventor has isolated an element which is more electrochemically noble than the rare earth element (for example, iron) in a process prior to the electrolytic deposition process. I thought. And this inventor considered the method of performing the wet separation process which utilized precipitation formation as this separation method, for example. Hereinafter, as an example of the wet separation treatment, an example in which iron (III) hydroxide is formed by precipitation is mentioned, and this process is referred to as "de-ironization treatment" or "de-ironization process".

  Furthermore, the inventor obtained not only the above-mentioned method but also obtained new problems arising with the above-mentioned method, in particular, problems which arise when the above-mentioned method is actually operated in a factory plant. The findings are as follows.

  First, in the case where the above-described exemplified method is carried out continuously in a plant, it is desirable that no local pH increase be involved in the deironing step. Moreover, as a hydroxide used as a precipitation formation agent at the time of performing a iron removal process, the hydroxide which consists of a metal electrochemically base rather than rare earth elements is suitable. The precipitation agent (for example calcium hydroxide) for precipitating iron as iron (III) hydroxide is a neutralization reaction of the acid medium (about 85% of the total OH-molar amount), and of iron (III) hydroxide Due to the need for the precipitation reaction (about 15% of the total OH-moles), a large dose has to be achieved. Instead of completely removing iron ions (III) as precipitates by hydroxylation by calcium hydroxide, amide-based rare earth metal salts having a relatively high content of a precipitating agent component (calcium) will be produced. That is, in the electrolytic deposition process described later, a relatively high ratio of calcium is mixed with the rare earth element in the electrolytic bath. In such a case, the solubility itself is constant, so that the content of the rare earth element decreases in the state of the amide-based rare earth metal salt before the electrolytic deposition step, which may cause the applied voltage to shift to the base side.

  In addition, when calcium hydroxide is used to produce iron (III) hydroxide, calcium is electrolyzed as the rare earth metal is recovered in the electrolytic deposition process when the plant is operated continuously. It will be accumulated inside. Normally, calcium should not precipitate in the electrolytic deposition step, but if calcium is accumulated excessively, the precipitation potential shifts to the noble side, so that calcium co-precipitates during the electrodeposition of the rare earth metal. Are concerned. In this case, the purity of the finally obtained rare earth metal may be lowered.

  Moreover, when performing said method continuously in a factory plant, if there is no secondary use of a precipitation formation agent, it must procure from the outside each time. If this happens, the cost of implementing the present invention at a plant will be enormous.

  Therefore, the present inventor preferably sets the rare earth content of the rare earth metal salt to be recovered to 90 wt. We have devised a method in which elements other than rare earth elements are hardly left in the electrochemical process by raising the content to at least% and purifying with high purity. In addition to precipitating and separating the noble element (iron) which is more electrochemically noble than the rare earth element in the process prior to the electrolytic deposition process, the oxidized magnetic powder inevitably formed in the process of eluting the rare earth element from VCM or the like After converting the rare earth element contained in the residue into a hydroxide, we conceived a method of utilizing the hydroxide of the rare earth element for the hydroxide reaction (iron removal treatment) of iron ion (III). That is, even during the so-called recycling operation of recovering rare earth elements from VCM or the like, the rare earth elements are recovered from the residue generated by the recycling operation and reused to remove unnecessary substances (iron hydroxide (III)) , I thought of a method that embodies the concept of recycling.

The aspect of this invention made based on the above knowledge is as follows.
The first aspect of the present invention is
In a method of recovering a rare earth element, the rare earth element is recovered from a resource containing iron and the rare earth element by electrolytic deposition of the rare earth element,
A first elution step of eluting iron and rare earth elements from the resources into an amide acid medium;
A second elution step of selectively leaching a rare earth element contained in the oxidized magnetic powder residue produced in the first elution step to a mineral acid under the condition of 1.5 <pH <3.5;
A rare earth hydroxide generation step of adding an acid / base neutralization reaction by adding a hydroxide of a metal more noble than the rare earth element selectively leached to the mineral acid in the second elution step;
A rare earth hydroxide addition step of mixing the rare earth hydroxide obtained in the rare earth hydroxide generation step and the amide-based acid medium obtained in the first elution step;
Iron (III) separation step of separating iron (III) hydroxide from the amide acid medium by forming and precipitating iron (III) hydroxide in the rare earth hydroxide addition step;
A salt formation step of forming an amide-based rare earth metal salt by concentrating the amide-based acid medium after the iron (III) hydroxide separation step;
An electrolytic deposition step of electrolytically depositing a rare earth element from the amide-based rare earth metal salt;
It is a recovery method of rare earth elements characterized by having.
However, the amide-based acid medium is an acid solution, and at least the amide-based acid medium in the salt formation step contains a hydrophobic anionic species capable of constituting an ionic liquid.
In a second aspect of the present invention, in the invention described in the first aspect,
In the electrolytic deposition step, a low-temperature melt of the amide-based rare earth metal salt is used as an electrolytic bath.
A third aspect of the present invention is the invention according to the first aspect, wherein
In the electrolytic deposition step, a liquid phase in which the amide-based rare earth metal salt is dissolved in an ionic liquid is used as an electrolytic bath.
In a fourth aspect of the present invention, in the invention according to any one of the first to third aspects,
At least one of alkali metal hydroxides, alkaline earth metal hydroxides and mixtures thereof which are more electrochemically rare than rare earth elements are used as a precipitation forming agent in the rare earth hydroxide formation step. Is a method of recovering a rare earth element characterized by
In a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects,
The rare earth hydroxide produced from the oxidized magnetic powder residue is characterized in that the weight ratio of the rare earth element is 90% or more.
A sixth aspect of the present invention is the invention according to any one of the first to fifth aspects, wherein
The amide rare earth metal salt is characterized in that the weight ratio of the rare earth element is 90% or more.
According to a seventh aspect of the present invention, in the invention according to any one of the first to sixth aspects,
The types of rare earths of the amide-based rare earth metal salts are characterized in that at least Nd and Dy are included.
The eighth aspect of the present invention is
In a rare earth element recovery apparatus for recovering a rare earth element from a resource containing iron and a rare earth element,
A first elution processing unit for eluting iron and rare earth elements from the resources into an amide acid medium;
A storage unit for storing a rare earth hydroxide generated from oxidized magnetic powder residue generated in the first elution processing unit;
An iron (III) separation part which forms iron hydroxide (III) and separates it by the rare earth hydroxide supplied from the storage part to the amide system acid medium obtained by the first elution processing part When,
A salt formation portion which forms an amide-based rare earth metal salt by concentrating an amide-based acid medium from which iron (III) hydroxide has been separated;
An electrolytic deposition unit for electrolytically depositing a rare earth element from the amide-based rare earth metal salt;
It is a collection | recovery apparatus of the rare earth elements characterized by having.
However, the amide-based acid medium is an acid solution, and at least the amide-based acid medium charged into the salt formation portion contains a hydrophobic anionic species capable of constituting an ionic liquid.

  According to the present invention, it is possible to provide a rare earth element recovery method and a rare earth element recovery apparatus that improve the quality of the recovered rare earth element while simplifying the work process.

It is a flowchart which shows the recovery method of the rare earth elements in this embodiment. A pH- electrograms _{Fe-H 2} O and _{Nd-H 2} O. FIG. 2 is a schematic view showing a three-pole electrolytic test apparatus used in Example 1. It is a graph which shows the result of having performed the XPS analysis with respect to the electrodeposit (Nd) obtained in Example 1. FIG. It is a graph which shows the result of having performed the XPS analysis with respect to the electrodeposit (Nd) obtained in Example 3. FIG. FIG. 16 is a graph showing the results of XPS analysis of the deposited material (Dy) obtained in Example 3. FIG.

Hereinafter, embodiments of the present invention will be described in the following order with reference to FIG. FIG. 1 is a flowchart showing a method of recovering a rare earth element in the present embodiment.
1. Recovery method of rare earth elements 1-A) Pretreatment step {Wet primary treatment}
1-B) First elution step 1-C) Iron hydroxide (III) separation step 1-D) Salt formation step {wet secondary treatment}
1-E) Second elution step 1-F) Rare earth hydroxide formation step 1-G) Rare earth hydroxide addition step {electrolytic deposition}
1-H) Electrochemical Step 1-H-a) Anodic Dissolution Step 1-H-b) First Electrolytic Deposition Step 1-H-c) Second Electrolytic Deposition Step In the present embodiment, as an iron group element Iron (Fe) is illustrated, and iron (III) hydroxide (Fe (OH) ₃ ) is illustrated as an iron group compound.

Hereinafter, the above steps 1-B) to 1-D) are also referred to as {wet primary treatment}, and the above steps 1-E) to 1-G) are also referred to as {wet secondary treatment}.
The main purpose of the {wet primary treatment} is to concentrate an amide-based acid medium from which iron (III) hydroxide has been removed to form an amide-based rare earth metal salt.
On the other hand, the main purpose of {wet secondary treatment} is to return the rare earth elements present in the oxidized magnetic powder residue produced after the first elution step as a hydroxide to the amide-based acid medium. More specifically, the rare earth element present in the oxidized magnetic powder residue is used as a material for producing iron (III) hydroxide in {wet primary treatment}.
In addition, about the structure which is not described below, you may employ | adopt the structure as described in well-known references, such as patent document 2 (Unexamined-Japanese-Patent No. 2012-87329).
Further, in the present embodiment, a method of recovering rare earth elements from real waste including rare earth magnets, such as a voice coil motor (VCM), a drive motor of a hybrid vehicle, a compressor of an air conditioner, etc., and an apparatus therefor will be described. . Of course, the present invention is applicable to all cases where the rare earth element is recovered from the resource in which iron and the rare earth element are mixed, except when the rare earth element is used in the form of a magnet.

<1. Recovery method of rare earth elements>
1-A) Pre-treatment process As a pre-treatment process, disassembly and separation process, a thermal demagnetization process, a plating peeling process, an oxidation roasting process, a pulverization process, and a classification process are performed. A known method may be adopted as the method, and the specific method is as described in the examples.
In the dismantling and sorting process, real wastes are dismantled and sorted, as briefly described below. And the member as a rare earth magnet is collect | recovered from each member dismantled and separated.
In the thermal demagnetization step, a member as a rare earth magnet is heated to eliminate residual magnetism of the member.
Next, when the plating layer is formed on the main surface of the member as the rare earth magnet, the plating peeling process is performed.
Thereafter, the oxidation roasting step is performed to a certain weight increase rate (about 1.3 times that before the oxidation treatment). The purpose of the oxidation roasting step is to suppress the elution amount of iron from the member as the rare earth magnet in the first elution step described later. In the first elution step described later, iron as well as the rare earth element is eluted in an amide-based acid medium described later. However, it is possible to selectively elute the rare earth element by converting it into the form of hematite (Fe ₂ O ₃ ) by performing the oxidation roasting step. This reduces the proportion of iron and facilitates the separation of iron and the rare earth element.
Since the particle size of the oxidized magnetic powder increases with sintering due to the oxidation roasting treatment, the pulverizing step using an automatic mill is performed. In the classification step, the finely divided oxidized magnetic powder is classified using an automatic sieve until the particle size becomes 25 μm or less. The oxidized magnetic powder having a particle size of 25 μm or less is used in the first elution step described later.

1-B) First Elution Step In the first elution step, it is a resource containing iron and a rare earth element, and a member as a rare earth magnet after passing through the plating and peeling step (hereinafter, also simply referred to as "resource"). Then, at least the rare earth element is eluted into the amide acid medium. In the present embodiment, “elution” of the first elution step refers to ionizing at least a rare earth element with an amide-based acid medium.

  The amide-based acid medium used in the present embodiment is an acid solution containing a hydrophobic anionic species capable of constituting an ionic liquid. If it is an amide-based acid medium (acid solution) having a hydrophobic anion species derived from this ionic liquid, it becomes possible to use an amide-based rare earth metal salt produced in a salt formation step described later as a low temperature melt; It becomes possible to apply a salt melt (liquid phase) to the electrolytic bath of the electrolytic deposition step.

As the amide-based acid medium, any known medium may be used as long as it satisfies the above conditions. For example, acid consisting of bisfluoromethylsulfonylamide anion: HFSA ((FSO ₂ ) ₂ NH), acid medium consisting of fluorosulfonyl (trifluoromethylsulfonylamide) anion: HFTA ((FSO ₂ ) (CF ₃ SO ₂ ) NH And the like may be used as an amide-based acid medium.

By the way, in the present specification, “hydrophobic anionic species” means that when an ionic liquid is synthesized from a cation precursor and an anion precursor by a metathesis reaction, the synthesis yield after removal of impurities derived from precursors such as halogen is 80 Indicates anionic species that can maintain% or more.
In addition, the “hydrophobic anionic species capable of constituting an ionic liquid” is, in other words, a hydrophobic anionic species capable of constituting an ionic salt when ionically bound to a proton (H ⁺ ). However, although the hydrophobic anion species is said, in the present embodiment, the resources are eluted to the amide-based acid medium. That is, what the ionic salt said here is made into aqueous solution turns into an amide system acid medium (acid solution) in this specification.

  However, it is not necessary to elute resources into mineral acids and then to allow hydrophobic ionic species to be present in the acid medium, but an acid solution comprising hydrophobic anionic species capable of constituting an ionic liquid, and further an amide-based acid as described below It is preferable to use the medium as the elution solution from the beginning in terms of recovery of the rare earth element. This is because an amide-based acid medium composed of a hydrophobic anion species capable of constituting an ionic liquid has a relatively high rare earth elution property as compared with mineral acids such as hydrochloric acid and nitric acid.

  By using an amide-based acid medium as an elution solution, it is possible to relatively easily elute the rare earth element out of the resources while maintaining high elution of the rare earth element, and finally recovering the rare earth element efficiently. Is possible.

  In addition, in the amide acid medium, there is also an advantage that the elution of iron is relatively low compared to the rare earth elements. In that case, it becomes possible to perform the below-mentioned salt formation process to the amide system acid medium which became low in iron, and the quality of a rare earth element can be improved finally.

  In the present specification, "amide-based acid medium" refers to a solution that satisfies the conditions of the above elution solution and contains an amide, and the amide-based acid medium is an ionic liquid represented by amic acid. It refers to an acid solution having an anion component. The "amide" is a compound having a structure in which ammonia or a primary or secondary amine and an oxo acid are dehydrated and condensed. Specifically, the "amide" in the present specification includes carboxylic acid amide, sulfonamide, phosphoric acid amide and the like.

The amide-based acid medium may be any one as long as it can elute the rare earth element. If it illustrates, the acid solution containing the amide | amido known as each of the compound of patent document 2 and other hydrophobic anionic species of an ionic liquid is mentioned. Specifically, bis (perfluoroalkylsulfonyl) amide (N [SO ₂ (CF ₂ ) _n CF ₃ ] ₂ ), bis (fluorosulfonyl) amide (N (SO ₂ F) ₂ ) (hereinafter referred to as An amide-based acid medium may also be used, including “HFSA”, trifluoromethylsulfonylamide ((CF ₃ SO ₂ ) ₂ NH) (hereinafter, also referred to as “HTFSA”), and the like. "HTFSA" is also referred to as 1,1,1-trifluoro-N-[(trifluoromethyl) sulfonyl] methanesulfonamide.

  The resource eluted in the first elution step may be any form of a rare earth metal oxide, a rare earth metal carbonate, a rare earth metal and an alloy of a rare earth metal. When the rare earth metal salt in the resource is a rare earth metal salt composed of a hydrophobic anion species weak in cation-anion interaction, it becomes easily soluble in a solution containing a hydrophobic anion species stronger in interaction.

The method of elution is not particularly limited as long as the method can efficiently elute the rare earth element from the resources to the amide acid medium. As a specific example, the first elution step may be performed by immersing the resource in an amide-based acid medium. In addition, the pH may be adjusted by adjusting the concentration of the amide acid medium by dilution or addition of an acid component. Adjustment of pH makes it possible to control the rate at which the resource elutes.
As another method of elution, as described in Patent Document 2, a voltage is applied to the resource to cause anodic dissolution, thereby dissolving iron and rare earth elements contained in the resource into an amide-based acid medium. There is a way to

Incidentally, the amide-based acid medium may be in the state of an elution solution containing a hydrophobic anionic species capable of constituting an ionic liquid in the step of the salt formation step described later. That is, amide acid medium the configurable hydrophobic anion is not a species mineral was time being eluted resources using (NO 3 nitrate (HNO _{3 -} ^-) or hydrochloric acid (HCl for ^Cl) inorganic acids such as) Also, a metal salt (for example, Li ⁺ TFSA ⁻ or Li ⁺ FSA ⁻ ) containing a hydrophobic anionic species capable of constituting an ionic liquid may be added to the solution after elution.
Even if the elution itself is performed using a relatively inexpensive mineral acid, the above-mentioned elution step may be completed by adding an appropriate amount of an amide-based acid component. If at least the amide-based acid medium applied to the salt formation step contains a hydrophobic anionic species capable of constituting an ionic liquid, the melt of the amide-based rare earth metal salt formed in the subsequent salt formation step is electrolytically deposited It becomes possible to apply to the electrolytic bath of a process.

Preferred specific conditions for carrying out this step are as follows. In addition, in this specification, "-" refers to the thing more than a predetermined value and below a predetermined value.
It is preferable to set temperature conditions of the range of 70-90 degreeC to the amide system acid medium in a 1st elution process. The reason for this is to increase the elution rate and to suppress the elution rate of hematite (Fe ₂ O ₃ ) to a low level without accompanied by evaporation of the amide-based acid medium.

The metal concentration in the amide-based acid medium is preferably 0.1 M to 1.0 M. The reason is that the elution rate of hematite (Fe ₂ O ₃ ) changes according to the acid concentration of the amide-based acid medium.

The reaction time for rare earth elution depends on the acid concentration of the amide acid medium, but in the case of 1.0 M amide acid medium, it is preferably 9 h to 12 h. The reason is that the magnet member after the oxidation roasting treatment is a poorly soluble rare earth oxide, and the first elution step takes 9 hours or more, and when performing a long reaction time exceeding 12 hours The amount of elution of hematite (Fe ₂ O ₃ ) is increased to suppress it.

After the resources are eluted in the first elution step, solid-liquid separation is performed. As a method of solid-liquid separation, you may use well-known methods, such as centrifugation.
The elution solution is subjected to the subsequent 1-C) iron (III) hydroxide separation step, followed by {wet primary treatment}. On the other hand, a solid, uneluted oxidized magnetic powder residue is recovered and transferred to {wet secondary treatment} described later.
For convenience of explanation, the description of {Wet primary treatment} is continued below.

1-C) Iron (III) hydroxide separation step In this step (hereinafter also referred to as "iron removal step"), first, with respect to an amide-based acid medium in which iron (Fe) and a rare earth element are eluted, An oxidation treatment step is required to oxidize iron ion species from divalent to trivalent (oxidation treatment step). The pH range in which the divalent Fe ions are converted to iron (II) hydroxide to form a precipitate is large in the range overlapping with the pH region in which the rare earth element is converted to hydroxide to form a precipitate. This means that the iron (II) hydroxide tends to coprecipitate with the rare earth hydroxide. In order to avoid this, it is necessary to oxidize Fe ions from divalent to trivalent.

  In this embodiment, only iron ions (III) are hydroxylated without being accompanied by precipitation of divalent iron (II) hydroxide or rare earth hydroxide by an oxidation treatment process without environmental impact such as oxygen bubbling. Process to precipitate as a thing.

  In addition, the Fe ions may be oxidized from divalent to trivalent by bubbling with ozone or chlorine, or other known oxidation methods may be used. This ensures oxidation of the total amount of Fe in the amide-based acid medium to trivalent ions.

  Then, after oxidizing the entire amount of Fe to trivalent ions, iron (III) hydroxide, which is one of the major features of the present embodiment, is formed to precipitate iron (III) hydroxide. , Separate from the amide acid medium. In the formation of iron (III) hydroxide, the hydroxide of the rare earth element contained in the oxidized magnetic powder residue produced in the first elution step is utilized. This is another major feature. The specific contents of this will be described in detail in the section of 1-E) second elution step to 1-G) rare earth hydroxide addition step which is {wet secondary treatment}.

1-D) Salt formation process A salt formation process is performed between an iron removal process and the electrolytic deposition process mentioned later. In the salt formation step, the amide acid medium is concentrated to form an amide rare earth metal salt containing a rare earth element. As a specific method, a known method for producing a salt from an acid solution may be used. As an example, spray heat drying with a spray dryer is performed on an amide-based acid medium under an inert atmosphere. Thereby, the moisture and the acid component in the amide-based acid medium can be removed, and a large amount of the dried amide-based rare earth metal salt containing the rare earth element can be generated. In addition, in the spray heat drying using a spray dryer, by adjusting the heat flux in the cyclone unit of the spray dryer, pulverization and drying of the amide rare earth metal salt can be simultaneously performed, which is effective for mass synthesis. If necessary, the metal salt may be heated to a temperature above the melting point of the amide-based rare earth metal salt to make it into a molten state, and vacuum drying may be performed, in order to further remove moisture in the amide-based rare earth metal salt.

The above contents are {wet primary treatment} until iron hydroxide (III) is formed and separated to form an amide rare earth metal salt.
Hereinafter, the details of {wet secondary treatment} in which the rare earth element contained in the oxidized magnetic powder residue generated in the first elution step is reused as a precipitation forming agent for producing iron (III) hydroxide will be described in detail. Describe.

1-E) Second elution step In this step, rare earth elements contained in the oxidized magnetic powder residue produced in the first elution step are selectively leached with a mineral acid.
In the above-mentioned 1-B) first elution step, iron and rare earth elements are eluted from the resources into an amide-based acid medium. On the other hand, among the resources, there are also rare earth elements which are not eluted into the amide-based acid medium, and these remain as oxidized magnetic powder residues in the amide-based acid medium which is the elution solution. This residue is mainly composed of oxidized magnetic powder, but also contains a predetermined amount of rare earth element.

A mineral acid is used to selectively leach rare earth elements in this step. The advantage of using a mineral acid is that it is possible to selectively leach rare earth elements and has a low cost acid medium. The contents will be described with reference to FIG.
FIG. 2 is a pH-electrogram of Fe-H ₂ O and Nd-H ₂ O, showing what kind of dissolved form can be most stably present in a solution of pH with each metal species. is there. Here, in the region of 2 <pH <7, Fe is most stable in hematite (Fe ₂ O ₃ ), and Nd is most stable in Nd ³⁺ . As a result, FIG. 2 shows that the degree of ionization (i.e., elution rate) of the rare earth species is improved. On the other hand, under the condition of pH <1, Fe stabilizes as Fe ³⁺ , and thus the dissolution rate of Fe is increased.
In consideration of the above contents and the findings of the present inventor, an acid solution meeting 1.5 <pH <3.5 is prepared and eluted to increase the elution rate of rare earth species and to limit the elution amount of Fe to an unlimited extent. It can be suppressed. As a result, it is possible to selectively leach rare earth elements.
Incidentally, as in FIG. 2 (Nd), a pH-potential diagram corresponding to a rare earth element such as Dy or Pr is already known, and a rare earth element other than Nd can be obtained by using a known pH-potential diagram for the rare earth element. It is also possible to selectively leach to mineral acids.

  Another advantage of using a mineral acid is that it is cheaper than using an acid medium derived from the anion component of the ionic liquid. When implementing the present invention in a factory plant, if the plant plant is continuously operated even with only a slight reduction in cost, it will ultimately lead to a significant cost reduction.

1-F) Rare Earth Hydroxide Generation Step In this step, the rare earth ion eluted into the mineral acid in the second elution step is a metal hydroxide composed of a metal electrochemically less noble than the rare earth element. A rare earth hydroxide is produced by a hydroxide precipitation reaction via an acid-base neutralization reaction. The metal hydroxide used here may be a known one (for example, sodium hydroxide or calcium hydroxide). However, the rare earth hydroxide produced in this step is added to the amide-based acid medium. That is, when the metal derived from the metal hydroxide is mixed with the rare earth hydroxide, there is a possibility that the electrolytic deposition step may be finally performed through the salt formation step. If so, the content of the rare earth element in the finally obtained precipitate may be reduced due to the metal derived from the metal hydroxide. Therefore, as the metal derived from the metal hydroxide, it is preferable to select one that is difficult to electrolytically deposit. Therefore, as a precipitation forming agent for producing a rare earth hydroxide, alkali metal hydroxides, alkali earth metal hydroxides, solid of a rare earth hydroxide, an aqueous solution, and the like, which are more electrochemically rare than the rare earth elements It is preferable to use at least one of the mixed solutions of

1-G) Rare Earth Hydroxide Addition Step After the precipitate (rare earth hydroxide) formed in the rare earth hydroxide formation step is recovered, in this step, the rare earth hydroxide obtained in the rare earth hydroxide formation step And the amide-based acid medium obtained in the first elution step. This step makes it possible to return the rare earth element which would otherwise be discarded back into the amide acid medium.

  This step is carried out to trigger the deferrozing step. Specifically, iron (III) hydroxide in the deironing step is produced by performing the rare earth hydroxide addition step which is this step. That is, the hydroxide of the rare earth element recovered by {wet secondary treatment} is utilized as the material of the deferroizing step in {wet primary treatment}.

  This makes it possible not only to return the rare earth elements that would otherwise be discarded back to the amide acid medium, but also to simultaneously produce iron (III) hydroxide. As a result, it becomes possible to utilize the rare earth elements that would otherwise be disposed of without any problems, and a series of recycling systems are completed.

  Moreover, in order to separate the iron (III) hydroxide from the amide acid medium and simultaneously add the rare earth element to the amide acid medium, the portion from which the iron (III) hydroxide is removed makes the rare earth element into the amide acid medium. Be added. As a result, the content of the rare earth element in the amide-based rare earth metal salt in the salt formation step is improved to 90% or more by weight. That is, high purity amide-based rare earth metal salts can be produced. In this case, there is no need to incorporate a continuous removal process for remaining elemental species in a series of continuous operations from wet treatment to electrolytic deposition. In addition, the current efficiency at the time of scale-up at the time of final electrolytic deposition of the rare earth element can be enhanced, and an electrodeposition material with high purity of the rare earth metal can be obtained.

  Furthermore, there is a great advantage in using rare earth hydroxides obtained from within a series of cycles of recovery of rare earth elements in the deironing step. First, there is no need to purchase a rare earth hydroxide separately, and the cost can be reduced. As described above, the effect is great when the present invention is implemented in a factory plant. If the prescribed amount of rare earth hydroxide can not be obtained by performing the above-mentioned rare earth hydroxide formation step only once, store it separately in a storage part for storing rare earth hydroxide. It is preferable to employ the method of performing the present process after a predetermined amount of rare earth hydroxide is stored, in order to efficiently carry out a series of cycles in a plant.

In addition, it is possible to solve the problems that arise as the plant is operated continuously. Specifically, if calcium hydroxide is used to form iron (III) hydroxide and an amide-based rare earth metal salt is produced in the salt formation step, the plant plant is During continuous operation, calcium is accumulated in the electrolytic bath. Normally, calcium should not be reduced, but it is also assumed that calcium co-precipitates in the electrodeposit if calcium is accumulated excessively. If this happens, the purity of the finally obtained rare earth element may be reduced.
Therefore, an amide-based rare earth metal having an extremely high rare earth element ratio in the salt formation step using the rare earth hydroxide obtained by {wet secondary treatment} which is treatment in a series of cycles as in this step By using salt, it is possible to construct an electrolytic environment in which calcium does not accumulate in the first place.
As a result, the rare earth content of the amide rare earth metal salt is extremely high, and it is used after being easily dissolved in a low temperature molten salt consisting of an element which is electrochemically weaker than the rare earth element in the electrolytic deposition process. Can.

Of course, when an amide-based rare earth metal salt is produced in the salt formation step, at least one of an alkali metal salt and an alkaline earth metal salt which are electrochemically inferior to the rare earth element and an amide-based rare earth metal salt are binary. Even if a system or ternary low temperature melt is to be formed, extremely advantageous effects can be obtained in the below-described electrolytic deposition process.
In the present embodiment, alkali metal hydroxides and alkaline earth metal hydroxides that are more electrochemically rare than rare earth elements are used in the rare earth hydroxide production step. Therefore, even if an amide-based rare earth metal salt forms a binary or ternary low-temperature melt with respect to these metal salts, the alkali metal or alkaline earth metal which is electrochemically basic in the electrolytic deposition step Almost no electrolytic deposition. As a result, it is possible to finally recover the rare earth element of high purity by electrolytic deposition.

1-H) Electrochemical Process In the electrochemical process, an electrolytic treatment for recovering a rare earth element is performed. In this process, in addition to the anodic dissolution process, an electrolytic deposition process is performed. Hereinafter, this process is simply referred to as "electrolytic deposition process". This electrolytic deposition process is performed by changing the conditions for each type of rare earth element after being divided into the first electrolytic deposition process and the second electrolytic deposition process. This will be described below.

1-Ha) Anodic Dissolution Step In the anodic dissolution step, the melt of the above-mentioned amide rare earth metal salt is used as it is as an electrolytic bath for electrolytic deposition of the rare earth element. The above-mentioned amide type rare earth metal salts are easily melted because they are extremely pure and are low temperature melts.
In addition, about the specific method in not using individual use of amide type rare earth metal salt but using an ionic liquid as an electrolytic bath, it mentions <3. Modifications Etc.> However, the method of Patent Document 2 or a known method may be used. The liquid to be dissolved may be a known ionic liquid having a wide potential window on the reduction side, or may be a melt of the amide-based rare earth metal salt in this embodiment.

The method of using the melt of an amide system rare earth metal salt as it is as an electrolytic bath is demonstrated using FIG. In addition, FIG. 3 is the schematic for demonstrating the three-electrode type electrolysis test apparatus 1 used in the below-mentioned Example. Here, the waste magnet member subjected to the demagnetization treatment is attached to the anode portion 4. And after making said amide type rare earth metal salt into a melt, the said anode part 4 is immersed in a rare earth melt with the cathode part 5. Then, the anode part 4 and the cathode part 5 of the DC power supply are conducted to perform anodic melting, and the demagnetized waste magnet member is dissolved in the rare earth melt. Here, not only the presence or absence of the plating peeling of the waste magnet member, but also the anodic part 4 is made of amide rare earth melt so that the iron ions in the rare earth magnet component do not diffuse into the amide rare earth melt (electrolytic bath) 21 It is necessary to separate the electrolytic bath 21 through the Vycor glass filter 9. In addition, as the cathode part 5, you may use what processed the copper plate in the substantially cylindrical shape like the below-mentioned Example, and the rare earth metal to precipitate and the inactive electrode whose crystal structure consists of a similar metal element are used. It does not matter.
Hereinafter, the details will be described later in the embodiment, and the reference numerals will be omitted.

1-H-b) First electrolytic deposition step In the electrolytic deposition step, the rare earth element is electrolytically deposited from the rare earth melt. And neodymium (Nd) is made to precipitate in the first electrolytic deposition process which is this process. As a specific method, the method of Patent Document 2 or a known method may be used. When the rare earth element is electrolytically deposited and the substance attached to the electrode is taken out, an element other than the rare earth element (for example, carbon or oxygen) may be contained. However, there is no change in the fact that the rare earth element is electrolytically deposited. Moreover, in the present embodiment, it is possible to separate iron and the rare earth element, which has been a major factor in lowering the quality of the rare earth element. Therefore, in the present specification, "electrolytic deposition of rare earth elements" refers to the state of "electrodeposited at least rare earth elements".

  The above method will be briefly described. As the anode part electrically connected to the power source for electrolysis, a soluble element composed of an element of the same kind as the rare earth element to be recovered (ie Nd) or a demagnetized waste magnet member Use an electrode. As the cathode part, a metal electrode which is an element which is electrochemically nobler than the rare earth element, and which is similar in crystal structure to the rare earth metal to be deposited is used. Further, since the demagnetized waste magnet member can be used for the anode part, it is efficient to carry out the above-mentioned anode dissolution step in the anode part and to carry out the first electrolytic deposition step in the cathode part.

1-Hc) Second electrolytic deposition step In the second electrolytic deposition step which is the present step, dysprosium (Dy) is deposited. The specific method is the same as in the first electrolytic deposition step, and electrolytic deposition is performed under the condition according to Dy. In addition, since the demagnetized waste magnet member can be used for the anode part, it is efficient to carry out the above-mentioned anodic dissolution process in the anodic part and the second electrolytic deposition process in the cathodic part.
In the second electrolytic deposition step, after the Nd is continuously recovered in the first electrolytic deposition step, an amide-based rare earth metal salt is appropriately replenished, so that an electrolytic environment having a high Dy concentration can be constructed. It becomes easy to collect Dy in the analysis and release process.

  According to the above-described method, the following effects can be obtained in addition to the above-described effects associated with "reuse of the rare earth element contained in the oxide magnetic powder residue after the first elution step".

  First, with the method of the present embodiment, it is not necessary to use the ionic liquid itself as the electrodeposition medium. Ionic liquids are relatively expensive and have many cost challenges when operating continuously in a factory plant. However, according to the method of the present embodiment, it is only necessary to use a substance capable of forming an ionic liquid as an anion in the amide-based acid medium, and it is not necessary to actually use the ionic liquid.

  Furthermore, since iron can be removed by a simple and efficient method of precipitation separation, it is possible to improve the quality of the recovered rare earth element. And although it mentions later by the item of an Example, it will become possible to make the recovery amount of rare earth elements increase according to the method as described in this embodiment. Furthermore, the purity of the recovered rare earth element can be improved. Specifically, even if the outermost surface of the recovered rare earth element is oxidized or carbon is attached as an impurity, the rare earth element having a relatively high purity in a portion other than the outermost surface (that is, a portion slightly deeper from the outermost surface) It becomes an element, and it becomes possible to finally obtain a large amount of high purity rare earth elements.

  And unlike the molten salt electrolysis method like patent document 1, the device design which gave special consideration to safety aspects, such as an electrolysis device which can control a corrosion reaction in high temperature, becomes unnecessary. As a result, it is possible to keep down the cost of the installation, and only a small amount of (heat and electrolysis) energy to be added.

  Further, unlike Patent Document 2, it is not necessary to separately perform electrolytic deposition of iron, and it is possible to suppress an increase in the number of times of the electrolytic deposition process. In addition, precipitation of iron (III) hydroxide allows the relative proportion of the rare earth element in the amide acid medium to be increased relative to the conventional recovery method. As a result, the need for performing an electrophoresis process for concentrating rare earth elements is eliminated. As a result, the economics of the work process can be improved.

  Further, unlike the solvent extraction method as in Patent Document 3, the composition ratio of the rare earth element in the electrolytic bath is higher than that in the conventional recovery method. Therefore, it is not necessary to have a multistage configuration as in the solvent extraction method. Furthermore, there is no need to separately electrolytically deposit iron, and it is possible to suppress an increase in the number of electrolytic deposition steps. As a result, the economics of the work process can be improved.

  As described above, it is possible to improve the quality of the recovered rare earth element while simplifying the work process.

<2. Recovery device for rare earth elements>
It is also possible to reflect the above technical idea on a recovery device of rare earth elements. Specifically, the rare earth element recovery apparatus in the present embodiment has the following configuration.
First elution processing section for eluting iron and rare earth elements from resources into amide acid medium Reservoir for storing rare earth hydroxide formed from oxidized magnetic powder residue generated in first elution processing section First elution processing section Iron hydroxide (III) separation part and iron hydroxide (III) which separate and produce iron (III) hydroxide by rare earth hydroxides charged from the storage part to the amide type acid medium obtained by The salt formation part which produces | generates an amide system rare earth metal salt by concentrating the amide system acid medium from which it was isolate | separated. The electrolytic deposition part which carries out the electrolytic deposition of the rare earth element from amide system rare earth metal salt. A part corresponding to each process in the method for recovering rare earth elements> may be separately provided. For example, "a second elution processing unit for selectively leaching rare earth elements contained in the oxidized magnetic powder residue generated in the first elution processing unit with a mineral acid" may be separately provided.
In the first electrolytic deposition step and the second electrolytic deposition step, separate processing units may be provided such as a first electrolytic deposition processing unit and a second electrolytic deposition processing unit, Third, fourth, etc. electrolytic deposition processing parts may be provided according to the number of types of rare earth elements.

<3. Modified example etc>
The technical scope of the present invention is not limited to the above-described embodiments, and includes various modifications and improvements as long as specific effects obtained by the constituent elements of the invention and the combination thereof can be derived.

(Iron-group elements and iron-group elements other than iron (Fe))
In this embodiment, an example in which iron (Fe ³⁺ ) among iron group elements is changed to a hydroxide is described. On the other hand, after all, if a compound containing an iron group element in an amide-based acid medium can be generated and the compound can be separated from the amide-based acid medium, it does not have to be changed to a hydroxide. As a specific example, the iron group element may be an oxide, or a sulfonated product or an iron group complex salt may be used to form a compound containing the iron group element, and the compound may be separated.

In addition, the solid compound does not have to precipitate, and may be suspended in a liquid. In that case, it becomes possible to perform solid-liquid separation of the compound containing an iron group element and the amide-based acid medium containing a rare earth element by known techniques such as filtration and centrifugation. That is, the above-mentioned "deironation step" is one of the specific examples, and "iron (III) hydroxide separation step" separates the compound by forming a compound containing an iron group element in the amide acid medium. "include.
In addition, even if the compound to be produced is a liquid, the compound can be separated from the amide-based acid medium using phase separation and the like. However, in consideration of the ease of separation from the amide-based acid medium, the compound is preferably solid. That is, it is preferable to perform solid-liquid separation of the compound from the amide acid medium.

  In order to clarify that the “technique for separating iron group elements by electrolytic deposition” as described in Patent Document 2 is different from the description described in the present specification, an iron (III) hydroxide separating step In the above, the expression "form hydroxide from iron ion (III) in amide acid medium" is used. On the other hand, the expression "electrolytic deposition of rare earth elements" is used in the electrolytic deposition step described later. That is, in the iron (III) hydroxide separation step, a chemical reaction that does not involve oxidation and reduction occurs, that is, the bond between the ion of the iron group element and the other ions. On the other hand, in the electrolytic deposition step, metal deposition accompanied by oxidation-reduction in which the ions of the rare earth element become zero is generated.

In the present embodiment, the iron group element is not particularly limited. In the present embodiment, although the case where the iron group element is Fe is described, it does not matter even if it contains iron group elements (Co, Ni) other than Fe. For example, instead of Fe, another iron group element (Co, Ni) may be subjected to the step corresponding to the above iron (III) hydroxide separation step.
Therefore, the "iron (III) separation process" can be referred to as "iron group compound separation process" if it is considered as a larger concept.

(Kind of rare earth element)
In the above embodiment, the type of the element in the rare earth element is not limited, but if practicability and easiness of operation are taken into consideration, lanthanum element (La), cerium element (Ce), praseodymium element (Pr), At least one element selected from neodymium element (Nd), samarium element (Sm), europium element (Eu), gadolinium element (Gd), terbium element (Tb) and dysprosium element (Dy) Is preferred.

(When the medium in which the amide rare earth metal salt is dissolved in the ionic liquid is used as the electrolytic bath)
Hereinafter, the case where an electrolytic bath is used as a medium in which an amide-based rare earth metal salt is dissolved in an ionic liquid will be described.

  In the case where the electrolytic deposition step is performed after the amide rare earth metal salt is dissolved in the ionic liquid, the steps up to the 1-D) salt formation step are performed as in the above embodiment. Then, the amide rare earth metal salt produced in the salt formation step is dissolved in the ionic liquid.

In addition, as an ionic liquid used as an electrolytic bath in 1-E) electrochemical process, as long as it can use as an electrolytic bath, you may use a well-known thing. As a specific example, the following may be used as the ionic liquid.
[A cationic component of quaternary phosphonium represented by the formula PR ¹ R ¹ R ¹ R ² , a cationic component of quaternary ammonium represented by the formula NR ³ R ³ R ³ R ⁴ or a cationic component represented by the following formula And, for example, bis (trifluoromethylsulfonyl) amide (N [SO ₂ CF ₃ ] ₂ ), bis (fluorosulfonyl) amide (N [SO ₂ F] ₂ ), trifluoromethanesulfonate (SO ₃ CF ₃ ), methane Sulfonate (SO ₃ CH ₃ ), trifluoroacetic acid (CF ₃ COO), thiocyanate (SCN), dicyanamide (N (CN) ₂ ), dialkyl phosphoric acid ((RO) ₂ POO)), dialkyl dithio phosphoric acid ((RO) ₂ PSS)), aliphatic carboxylic acid (RCOO), hexafluorophosphate _(PF 6), Tetorafuru Roboreto (BF ₄₎ and those composed of at least one anionic component selected from the group consisting of halogen or the like. "
In addition, as conditions of the group applicable to the symbol in the said formula of onium cation, it is as follows.
R ¹ is a linear, branched or alicyclic alkyl group having 2 to 6 carbon atoms which may have a substituent. Alternatively, R ¹ represents an alkoxyalkyl group represented by R′—O— (CH ₂ ) _m — (R ′ represents a methyl group or an ethyl group, and m represents an integer of 1 to 4).
R ² is a linear, branched or alicyclic alkyl group having 1 to 14 carbon atoms which may have a substituent.
The plurality of R ^{1 s} may be the same or different.
R ¹ and R ² are different from each other, and the total number of carbon atoms of the phosphonium cation is 20 or less.
R ³ is a linear, branched or alicyclic alkyl group having 2 to 6 carbon atoms which may have a substituent.
R ⁴ is a linear, branched or alicyclic alkyl group having 1 to 14 carbon atoms which may have a substituent.
The plurality of R ^{3 s} may be the same or different.
R ³ and R ⁴ are groups different from each other, and the total number of carbon atoms of the ammonium cation is 20 or less.
N represents an integer of 0 to 5;
· ^{R 5} represents an alkyl group having 1 to 5 carbon atoms, ^{R 6} represents a methyl group or an ethyl group, ^{m *} is an integer of 4 or 5, ^{n *} is an integer of 1 to 4.

  Here, the temperature at which the ionic liquid is used as an electrolytic bath is not particularly limited as long as the liquid phase state can be maintained, but as the cation component, phosphonium cation of low carbon chain, as the anion component Fluoromethylsulfonyl) amide is preferred in that it exhibits low viscosity.

  In addition, one part anionic species which comprise said ionic liquid are applicable also to the anionic species which comprise amide system acid medium. As described above, the amide-based acid medium used in the first elution step is preferably a solution containing an anionic species that constitutes the ionic liquid. Therefore, the anion species of the amide-based acid medium used in the first elution step may be one of the anion species of the above-mentioned ionic liquid.

The configuration example that comprehensively describes the above various contents is as follows.
[In a method of recovering a rare earth element, wherein the rare earth element is recovered from a resource containing an iron group element and a rare earth element by electrolytic deposition of the rare earth element;
A first elution step of eluting iron group elements and rare earth elements from the resources into an amide acid medium;
A second elution step of selectively leaching a rare earth element contained in the oxidized magnetic powder residue produced in the first elution step with a mineral acid;
A rare earth hydroxide generation step of hydroxylating the rare earth element selectively leached to the mineral acid in the second elution step with a metal hydroxide;
A rare earth hydroxide addition step of adding the rare earth hydroxide generated in the rare earth hydroxide generation step to the amide-based acid medium;
An iron-group compound separation step of separating a hydroxide of an iron-group element generated by the rare earth hydroxide addition step from the amide-based acid medium;
A salt formation step of forming an amide rare earth metal salt by concentrating the amide acid medium after the iron group compound separation step;
An electrolytic deposition step of electrolytically depositing a rare earth element from the amide-based rare earth metal salt;
A method of recovering a rare earth element comprising:
However, the amide-based acid medium is an acid solution, and at least the amide-based acid medium in the salt formation step contains a hydrophobic anionic species capable of constituting an ionic liquid. "
However, the above configuration example is merely an example, and various modifications are possible. In particular, various conditions (specific additives, range of pH, separation method of hydroxide of iron group element, and the like) in each of the above steps can be appropriately adjusted.

Next, the present invention will be specifically described by way of examples. Of course, the present invention is not limited to the following examples.
In the following examples, the case where the iron group element is Fe will be described in detail.

<Example 1> (Electrolytic deposition test of rare earth elements using low temperature melt of amide-based rare earth metal salt)
In the present embodiment, the step of recovering the rare earth element was carried out using the used VCM for 3.5 inch HDD according to the flow chart shown in FIG.

  1-A) The pretreatment process was performed as follows.

  In the dismantling and sorting process, first, real waste was dismantled, the VCM was separated, and then only the member as the rare earth magnet was recovered from the VCM.

  The thermal demagnetization process was performed according to the following procedure. That is, a member as a rare earth magnet was placed on a firing setter, held in an alumina crucible, and then introduced into an electric furnace. As a temperature program of the thermal demagnetization step, the temperature rising / falling speed to the Curie temperature (310 ° C.) was set at 100 ° C./h under the atmosphere. This thermal demagnetization step suppresses the formation of an oxide film on the surface of a member as a rare earth magnet, while the initial magnetic flux density: 410 to 445 mT, the residual magnetic flux density: 0.01 mT (demagnetizing factor: 99.9% or more) I lowered it. This makes subsequent handling of the member as the rare earth magnet easy.

  In the plating peeling step, the Ni-Cu-Ni plated layer on the surface of the rare earth magnet member was peeled by physical polishing treatment.

  In the oxidation roasting step, after the polishing debris was sufficiently removed with distilled water, the rare earth magnet member after peeling off the plating layer was dried in a dryer. The rare earth magnet members were crushed using an automatic mill. Thereafter, the pulverized rare earth magnet members were spread in an alumina container, and an oxidation roasting process was performed under the condition of 860 ° C. for 2 hours in the air atmosphere. After the oxidized magnetic powder member was pulverized again, the oxidation roasting step was performed under the conditions of 860 ° C. for 2 hours.

  Thereafter, the pulverizing step using an automatic mill was carried out, and using an automatic sieve, a classification step was carried out to classify the particles to a particle size of 25 μm or less, thereby obtaining oxidized magnetic powder having a particle diameter of 25 μm or less.

  1-B) In the first elution step, 250 ml of a HTFSA (1.0 M) solution was used as an amide-based acid medium. 10 g of the oxidized magnetic powder obtained after the pretreatment step was introduced into the HTFSA solution. Then, on a hot stirrer, elution was performed for 165 h at 70 ° C. and 700 rpm. After the elution treatment, the unreacted oxidized magnetic powder residue was subjected to solid-liquid separation by centrifugation and filtration to obtain a residue and a solution (amide-based acid medium).

Next, the residue was subjected to 1-E) second elution step. Specifically, the rare earth element (Pr, Nd, Dy) is prepared by mixing the mineral acid hydrochloric acid (concentration 1.0 M, volume 250 ml) and the residue to adjust to pH 1.51 (pH after elution). Were selectively leached to obtain a leachate.
Then, 1-F) rare earth hydroxide production | generation process was performed. Specifically, sodium hydroxide (concentration 1.0 M), which is a metal hydroxide, was administered stepwise to the leaching solution from the initiation of pH 6.5, and was added to the leaching solution until the termination of precipitation was 11.5. The total amount of the water-precipitated material thus obtained was 71.85 g. In addition, it identified by XRD that the precipitate is a rare earth hydroxide. In addition, the above-mentioned procedure was performed 5 times in all, five samples were put together, five were produced, and the ICP-AES analysis was performed with respect to each sample. The composition analysis result in each sample obtained by ICP-AES analysis, that is, the composition ratio of the rare earth hydroxide produced in the wet secondary treatment was as shown in Table 1.

In addition, the meaning of the item of "M (OH) _n " in a table | surface and "n" is as follows. First, in ICP-AES, all types of metal cations can be determined quantitatively. And, the total amount of cations = the total amount of anions. As a result, the anion is considered to be attributable to OH, and the molecular weight of M (OH) _n is calculated therefrom. In addition, M means a metal. And since OH itself has a fixed molecular weight, the value of the item of _n is determined from the molecular weight shown by M (OH) _n .

And the 1-G) rare earth hydroxide addition process of adding the said rare earth hydroxide to the said amide system acid medium which is elution solution was performed. At that time, as described in the above embodiment, treatment was performed to avoid coprecipitation of divalent Fe ions and rare earth elements. Specifically, after adding a rare earth hydroxide until the pH of the elution solution reaches 4.5, trivalent Fe ions are obtained by bubbling oxygen under a flow rate of 120 mL / min for 45 minutes. Oxidized to. The absence of divalent Fe ions in the amide acid medium was confirmed using 1,10-phenanthroline indicator. As a result, a precipitate of Fe (OH) ₃ was formed in the elution solution. The precipitate was removed by a centrifuge under conditions of 10000 rpm and 10 minutes, and a 1-C) iron (III) hydroxide separation step was performed.
In addition, as a result of analyzing the obtained solution by ICP-AES, it was confirmed that Fe was 0 ppm, the wet separation rate was 100%, and the weight ratio of the rare earth element was 90% or more.

After the 1-C) iron (III) hydroxide separation step, in the 1-D) salt formation step, an amide-based acid medium was spray-dried by a spray dryer to obtain an amide-based rare earth metal salt. Spray dryer temperature is: evaporation tube temperature: 200 ° C, cyclone recovery part temperature: 125 ° C, blower flow rate: 0.68m ³ / min, atomizing: 110kPa, introduction flow rate of amide acid medium: 0.2L / h went. The introduced gas to the cyclone recovery unit utilized dry nitrogen. Thus, an amide-based rare earth metal salt was formed. The compositional analysis results of the amide-based rare earth metal salt in each sample are as shown in Table 2.

  A three-electrode electrolytic test apparatus 1 used in the 1-H) electrochemical process in the present embodiment is shown in FIG.

  The three-electrode electrolytic test in the present example was performed using a three-electrode electrolytic test apparatus 1 adopting the following configuration. As an electrode configuration in the electrolytic test apparatus, a three-electrode system (working electrode: Cu substrate, counter electrode: demagnetized Nd-Fe-B rod, pseudo reference electrode: Pt wire) shown in FIG. 3 was used. The outline will be described below.

  The three-electrode electrolytic test apparatus in the present embodiment has an anode part 4, a glass member 8 containing the anode part 4, a cathode part 5, a pseudo reference electrode part 12, and an electrolysis cell 13 capable of containing these. Further, although not shown, an electrolytic test apparatus capable of measuring the integrated amount of electricity is also provided.

  From the electrolytic test apparatus, the anode 4 and the cathode 5 are electrically connected on the basis of the potential of the pseudo reference electrode 12. The addition of the pseudo reference electrode unit 12 enhances the accuracy of the applied potential.

  In addition, the heat-resistant wool 14 which covers the electrolysis cell 13, the mantle heater 15 on the outer side, and the hot stirrer 16 are provided in the lower part of these. A stirrer 17 is provided inside the electrolysis cell 13. Further, the upper portion of the electrolytic cell 13 is held in a sealed state by a silicon plug 18. A glass member 8 (anode portion 4), a cathode portion 5, a pseudo reference electrode portion 12 and a thermocouple 19 for measuring the temperature of the electrolytic bath are provided so as to penetrate the silicon plug 18.

  In the present embodiment, the demagnetized waste magnet member is used as the anode unit 4. The waste magnet member is supplied with a predetermined applied voltage from an anode lead wire (not shown). The anode portion 4 is disposed in a hollow glass member 8 made of soda lime glass. In addition, the glass filter 9 (Vycor glass filter) is installed in the front-end | tip (ground side) of the glass member 8. FIG.

  A melt of an amide-based rare earth metal salt to be an electrolytic bath is introduced into the electrolytic cell. At the same time, a melt of an amide-based rare earth metal salt is also introduced into the glass member 8 to immerse the demagnetized waste magnet member.

  In addition, due to the functionality of the glass filter 9, the amide-based rare earth melt (anode side) 22 does not diffuse into the amide-based rare earth melt (electrolysis bath) 21 to be an electrolytic bath, and is dissolved at the anode portion 4 The magnetized waste magnet member and the insoluble substance are held by the anode unit 4. Thus, the three-electrode electrolytic test apparatus in this example was designed. The glass filter 9 has a structure in which current flows by increasing the applied voltage.

In the present example, in order to improve the working efficiency, the 1-H-a) anodic dissolution step and the 1-H-b) first electrolytic deposition step were simultaneously performed.
In the first electrolytic deposition step in this example, the anode portion 4 was a waste magnet member subjected to demagnetization, and the cathode portion 5 was a Cu substrate. The cathode portion 5 has a structure in which the electrode area is increased by making the Cu substrate cylindrical. A thermally stable Pt wire was used as a pseudo reference electrode. Then, deposition of Nd was performed under the conditions of a bath salt temperature: 190 ° C., an electrolytic atmosphere: Ar, an applied voltage: −3.2 V, and a total amount of electricity: 350 C. As a result, the anode current efficiency was 90.3%, and the cathode deposit was 121.9 mg, and a very high anode current efficiency was obtained. The anode current efficiency was calculated from the ratio of the actual weight change to the theoretical weight reduction of the anode calculated from the total amount of electricity (the same applies hereinafter).

And the result of having carried out the XPS analysis (X-ray photoelectron spectroscopy: X-ray Photoelectron Spectroscopy: XPS) of the obtained electrodeposit is shown in FIG. In the Nd3d _5/2 spectrum, in the case of Nd metal, a peak occurs in the range of 980.5-981.0 eV. In the case of Nd ₂ O ₃ , a peak is generated in the range of 9817.7-982.3 eV. The peak is prominent at 981.5 eV at a depth of 0.15 μm from the outermost surface layer (FIG. 4 (a)), which is an intermediate state between the oxide phase and the metal phase. On the other hand, at a depth of 1.25 μm from the outermost surface layer (FIG. 4B), the peak is remarkable at 980.7 eV, and the formation of a metal phase could be confirmed.

<Example 2> (Electrolytic deposition test of rare earth elements when an amide-based rare earth metal salt is dissolved in an ionic liquid)
In this example, an example in which the electrolytic deposition step is performed after dissolving the amide-based rare earth metal salt generated in the salt formation step in the ionic liquid was applied. And in this example, it described about the result of having recovered Nd. In the following, the items that are not specified otherwise are the same as in <Example 1>.

  The process up to the 1-D) salt formation step was the same as in <Example 1>.

In this example, after dissolving the amide-based rare earth metal salt obtained as described above in an ionic liquid (P ₂₂₂₅ TFSA) at a concentration of 0.25 M, a stirring-type vacuum drying apparatus using an oil bath is used. The liquid phase subjected to a drying treatment for 72 h under conditions of 110 ° C. and 300 rpm was used as an electrolytic bath. As a result of measuring the water content in the electrolytic bath with a Karl Fischer moisture meter equipped with a water vaporizer, it was confirmed to be 63.4 ppm.

The three-electrode electrolytic test apparatus 1 shown in FIG. 3 is also used in this embodiment.
An ionic liquid (electrolytic bath) (corresponding to reference numeral 21) in which an amide-based rare earth metal salt to be an electrolytic bath is dissolved is supplied to the electrolytic cell 13. At the same time, a rare earth metal salt dissolved ionic liquid (anode side) (corresponding to reference numeral 22) is charged into the glass member 8 and an ionic liquid (anode side) 22 in which an amide-based rare earth metal salt is dissolved. The anode portion 4 which is a waste magnet member subjected to demagnetization treatment is immersed.

  An ionic liquid (anode side) 22 in which an amide-based rare earth metal salt is dissolved due to the functionality of the glass filter 9 is an ionic liquid in which an amide-based rare earth metal salt is dissolved into the electrolytic cell 13 to be an electrolytic bath. The demagnetized waste magnet member and the insoluble substance that do not diffuse into the (electrolytic bath) 21 and dissolve as the anode unit 4 are held in the vicinity of the anode unit 4. Thus, the three-electrode electrolytic test apparatus in this example was designed.

And the electrolysis test was done in the glove box whose water content is 1 ppm or less. During the electrolytic test, the electrolytic bath was stirred at 300 rpm by a stirrer. With the progress of electrolysis, the next reaction proceeds in each electrode.
(Anode reaction)
3/2 Fe → 3/2 Fe (II) + 3 e ⁻ ,
^{RE → RE (III) + 3e} - (RE = Pr, Nd, Dy)
(Cathode reaction)
^{Nd (III) + 3e - →} Nd

  The Fe (II) produced from the anodic reaction does not diffuse into the electrolytic bath, and the diffusion is suppressed by the Vycor glass filter. Also, Nd dissolution on the anode side is dissolution from the Nd-Fe-B rod component, and Nd deposition on the cathode is deposition of Nd (III) from amide rare earth metal ions (VCM component) in the electrolytic bath .

  Deposition of Nd was performed under the conditions of a bath salt temperature: 100 ° C., an electrolytic atmosphere: Ar, an applied voltage: −3.2 V, and a total amount of electricity: 250 C. As a result, the anode current efficiency was 92.7%, and the cathode deposit was 87.5 mg, and an extremely high anode current efficiency was obtained.

Next, as a result of XPS analysis of the obtained electrodeposit, in the Nd3d _5/2 spectrum, the peak at 981.5 eV was remarkable in the outermost surface layer, and it was an intermediate state between the oxide phase and the metal phase. On the other hand, at a depth of 0.75 μm from the outermost surface layer, a peak of 980.8 eV is remarkable, and formation of a metal phase could be confirmed.

Example 3
In the present embodiment, the step of recovering the rare earth element was carried out using the used VCM for 3.5 inch HDD according to the flow chart shown in FIG.

  1-A) The pretreatment step was performed in the same manner as in Example 1 except that the calcination temperature in the oxidation roasting step was changed to 900 ° C., 3 h.

In the oxidation roasting step, after the polishing debris was sufficiently removed with distilled water, the rare earth magnet member after peeling off the plating layer was dried in a dryer. The rare earth magnet members were crushed using an analysis mill. Thereafter, the pulverized rare earth magnet members were spread in an alumina container and subjected to an oxidation roasting process under the conditions of 900 ° C. and 3 h in the air atmosphere. The Nd ₂ O ₃ layer, the Fe ₂ O ₃ layer, the Fe ₃ O ₄ layer, and the NdFeO ₃ layer were confirmed from the XRD of the oxidized magnetic powder. Thereafter, the pulverizing step using an analysis mill was carried out, and using an automatic sieve, the classifying step was carried out to classify the particles to a particle size of 150 μm or less, thereby obtaining oxidized magnetic powder having a particle diameter of 100 μm or less.

  In the 1-B) elution step, 250 mL of a HTFSA (1.0 M) solution was used as an amide-based acid medium. Twenty-five grams of the oxidized magnetic powder obtained after the pretreatment step was gradually introduced into the HTFSA solution. Then, on a hot stirrer, elution was performed for 72 h at 50 ° C. and 500 rpm. After the elution treatment, the unreacted oxidized magnetic powder residue was subjected to solid-liquid separation by centrifugation and filtration to obtain a residue and a solution (amide-based acid medium).

  Next, the residue was subjected to 1-E) second elution step. Specifically, the rare earth element (Pr, Nd, Dy) is prepared by mixing the mineral acid hydrochloric acid (concentration 1.0 M, volume 250 ml) with the residue to adjust to pH 1.02 (pH after elution). Were selectively leached to obtain a leachate.

Then, 1-F) rare earth hydroxide production | generation process was performed. Specifically, potassium hydroxide which is a metal hydroxide, strontium hydroxide or barium hydroxide (concentration 1.0 M) is dropped to the above-mentioned leaching solution from pH 6.0 to 6.5 of precipitation start, pH 11 of precipitation end 0 to 11.5 was added to the leachate. In addition, it was confirmed by XRD that the precipitate is a rare earth hydroxide. In addition, it implemented to the kind of precipitation formation agent, and performed the ICP-AES analysis with respect to each sample. The composition analysis result in each sample obtained by ICP-AES analysis, that is, the composition ratio of the rare earth hydroxide produced in the wet secondary treatment was as shown in Table 3.

And the 1-G) rare earth hydroxide addition process of adding the said rare earth hydroxide to the said amide system acid medium which is elution solution was performed. At that time, as described in the above embodiment, treatment was performed to avoid coprecipitation of divalent Fe ions and rare earth elements. Specifically, after adding the rare earth hydroxide until the pH of the elution solution reaches 3.6, trivalent Fe ions are obtained by bubbling oxygen under a flow rate of 100 mL / min for 120 minutes. Oxidized to. The absence of divalent Fe ions in the amide acid medium was confirmed using 1,10-phenanthroline indicator. As a result, a precipitate of Fe (OH) ₃ was formed in the elution solution. The precipitate was removed by a centrifuge under conditions of 10000 rpm and 10 minutes, and a 1-C) iron (III) hydroxide separation step was performed.
In addition, as a result of analyzing the obtained solution by ICP-AES, it was confirmed that Fe was 0 ppm, the wet separation rate was 100%, and the weight ratio of the rare earth element was 90% or more.

After the 1-C) iron (III) hydroxide separation step, in the 1-D) salt formation step, an amide-based acid medium was spray-dried by a spray dryer to obtain an amide-based rare earth metal salt. The spray dryer has an evaporation tube temperature: 200 ° C., a cyclone recovery unit temperature: 125 ° C., a blower flow rate: 0.48 to 0.60 m ³ / min, atomizing: 100 to 110 kPa, an introduction flow rate of an amide-based acid medium: 175 mL / It went on condition of h. The atomizing gas of the evaporation tube utilized 99.95% or more of pressurized dry nitrogen. Thus, an amide-based rare earth metal salt was formed. The compositional analysis result of the amide-based rare earth metal salt in each sample is as shown in Table 4.

The same three-electrode electrolytic test apparatus used in the 1-H) electrochemical process in this example was used. In the electrolytic bath, 25 mL of an ionic liquid [P ₂₂₂₅ ] [TFSA] was used to dissolve a rare earth salt (in the case of using potassium hydroxide as a precipitation forming agent) at a concentration of 0.1 mol%. After dissolving in the ionic liquid, the water content in the electrolytic bath was reduced to 38 ppm by vacuum stirring dehydration using an oil bath.

  In the first electrolytic deposition step in this example, the anode portion 4 was a waste magnet member subjected to demagnetization, and the cathode portion 5 was a Cu substrate. The cathode portion 5 has a structure in which the electrode area is increased by making the Cu substrate cylindrical. A thermally stable Pt wire was used as a pseudo reference electrode. Then, deposition of Nd was performed under the conditions of a bath salt temperature: 100 ° C., an electrolytic atmosphere: Ar, an applied voltage: −3.25 V, and a total amount of electricity: 328 C. As a result, anode current efficiency: 94.3%, cathode deposit: 107. It was 8 mg, and very high anode current efficiency was obtained. The anode current efficiency was calculated from the ratio of the actual weight change to the theoretical weight reduction of the anode calculated from the total electric quantity. The Cu substrate on the cathode side was exchanged for each Nd electrodeposition test, and the constant potential setting conditions were maintained to continue the continuous Nd electrolysis test. A total of two consecutive Nd electrolysis tests were performed, and the total amount of electricity was 576C. The average current efficiency on the anode side in two consecutive Nd electrolysis tests was 93.8%. Final cathode deposit: 210.6 mg could be recovered, and the average current efficiency on the cathode side was 73.4%.

And the result of having carried out the XPS analysis (X-ray photoelectron spectroscopy: X-ray Photoelectron Spectroscopy: XPS) of a part of obtained electrodeposit is shown in FIG. In the Nd3d _5/2 spectrum, in the case of Nd metal, a peak occurs in the range of 980.5-981.0 eV. In the case of Nd ₂ O ₃ , a peak is generated in the range of 9817.7-982.3 eV. The peak was prominent at 981.2 eV at a depth of 0.02 μm from the outermost surface layer, and was an intermediate state between the oxide phase and the metal phase. On the other hand, at a depth of 0.55 μm from the outermost surface layer, a peak of 980.8 eV was remarkable, and the formation of the Nd metal phase could be confirmed. Even when the depth direction was increased to 0.85 μm, the peak at 980.5 eV was significant, and it was confirmed that this was the Nd metal phase.

After replacing the Cu substrate in the second electrolytic deposition step in the present example, the Dy electrodeposition test was performed. Bath salt temperature: 100 ° C., electrolytic atmosphere: Ar, applied voltage: −3.80 V, total electric charge: Dy deposition was performed under the conditions of 75C. As a result, the anode current efficiency was 89.6%, and the cathode deposit was 30.2 mg, and a relatively high anode current efficiency was obtained. The result of XPS analysis of the obtained electrodeposit is shown in FIG. In the Dy3d _5/2 spectrum, at a depth of 0.05 μm from the outermost layer, a peak was generated outside the range of 1295.5 to 1297.0 eV, suggesting a mixture of the Dy metal phase and the Dy oxide phase. At a depth of 0.85 μm from the outermost surface layer, a peak is generated in the range of 1295.5 to 1297.0 eV, and it can be confirmed that it is a Dy metal phase.

DESCRIPTION OF SYMBOLS 1 ... 3 electrode type electrolytic testing apparatus, 4 ... anode part, 5 ... cathode part, 8 ... glass member, 9 ... glass filter, 12 ... pseudo reference electrode part, 13 ... electrolysis cell, 14 ... heat resistant wool, 15 ... mantle heater 16 Hot stirrer, 17 Stirrer, 18 Silicon plug, 19 Thermocouple, 21 Melt of amide rare earth metal salt or liquid phase obtained by dissolving amide rare earth metal salt in ionic liquid (electrolytic bath) , 22 · · · Melt of amide rare earth metal salt or liquid phase obtained by dissolving amide rare earth metal salt in ionic liquid (anode side)

Claims (8)

In a method of recovering a rare earth element, the rare earth element is recovered from a resource containing iron and the rare earth element by electrolytic deposition of the rare earth element,
A first elution step of eluting iron and rare earth elements from the resources into an amide acid medium;
A second elution step of selectively leaching a rare earth element contained in the oxidized magnetic powder residue produced in the first elution step to a mineral acid under the condition of 1.5 <pH <3.5;
A rare earth hydroxide generation step of adding an acid / base neutralization reaction by adding a hydroxide of a metal more noble than the rare earth element selectively leached to the mineral acid in the second elution step;
A rare earth hydroxide addition step of mixing the rare earth hydroxide obtained in the rare earth hydroxide generation step and the amide-based acid medium obtained in the first elution step;
Iron (III) separation step of separating iron (III) hydroxide from the amide acid medium by forming and precipitating iron (III) hydroxide in the rare earth hydroxide addition step;
A salt formation step of forming an amide-based rare earth metal salt by concentrating the amide-based acid medium after the iron (III) hydroxide separation step;
An electrolytic deposition step of electrolytically depositing a rare earth element from the amide-based rare earth metal salt;
A method of recovering a rare earth element comprising:
However, the amide-based acid medium is an acid solution, and at least the amide-based acid medium in the salt formation step contains a hydrophobic anionic species capable of constituting an ionic liquid.   The method for recovering a rare earth element according to claim 1, wherein a low temperature melt of the amide-based rare earth metal salt is used as an electrolytic bath in the electrolytic deposition step.   The method for recovering a rare earth element according to claim 1, wherein in the electrolytic deposition step, a liquid phase in which the amide-based rare earth metal salt is dissolved in an ionic liquid is used as an electrolytic bath.   At least one of alkali metal hydroxides, alkaline earth metal hydroxides and mixtures thereof which are more electrochemically rare than rare earth elements are used as a precipitation forming agent in the rare earth hydroxide formation step. The method for recovering rare earth elements according to any one of claims 1 to 3, characterized in that   The method for recovering a rare earth element according to any one of claims 1 to 4, wherein the rare earth hydroxide produced from the oxidized magnetic powder residue has a weight ratio of the rare earth element of 90% or more.   The method for recovering a rare earth element according to any one of claims 1 to 5, wherein a weight ratio of the rare earth element of the amide-based rare earth metal salt is 90% or more.   The method for recovering a rare earth element according to any one of claims 1 to 6, wherein the kind of the rare earth of the amide-based rare earth metal salt contains at least Nd and Dy. In a rare earth element recovery apparatus for recovering a rare earth element from a resource containing iron and a rare earth element,
A first elution processing unit for eluting iron and rare earth elements from the resources into an amide acid medium;
A storage unit for storing a rare earth hydroxide generated from oxidized magnetic powder residue generated in the first elution processing unit;
An iron (III) separation part which forms iron hydroxide (III) and separates it by the rare earth hydroxide supplied from the storage part to the amide system acid medium obtained by the first elution processing part When,
A salt formation portion which forms an amide-based rare earth metal salt by concentrating an amide-based acid medium from which iron (III) hydroxide has been separated;
An electrolytic deposition unit for electrolytically depositing a rare earth element from the amide-based rare earth metal salt;
A recovery apparatus of a rare earth element characterized by having:
However, the amide-based acid medium is an acid solution, and at least the amide-based acid medium charged into the salt formation portion contains a hydrophobic anionic species capable of constituting an ionic liquid.