JP6348796B2 - Recovery method of rare earth elements using ionic liquid - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a rare earth element recovery method and a rare earth element recovery apparatus using an ionic liquid, and more particularly, an electric analysis after selectively extracting a rare earth element into an ionic liquid (organic phase solution) with a solvating extractant. The present invention relates to a rare earth element recovery method and a rare earth element recovery device for recovering rare earth elements.

  Rare metals are a collective term for six types of platinum group rare metals with high resource value, nine types of national reserve rare metals, and 17 types of rare earths (hereinafter referred to as “rare earth elements”) with high uneven distribution. Among rare metals, rare earth elements have similar chemical properties within the lanthanoid series, and are electrochemically extremely basic elements. Therefore, mutual separation and metal refining have been difficult. In recent years, the Ministry of the Environment, as a recycling society formation promotion research project, based on the Small Household Appliance Recycling Law, which came into effect on April 1, 2013, recycling of rare metals from used small electronic devices and waste treatment technology Development has been emphasized.

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

  One of the effective members in the used small electronic devices is a voice coil motor (VCM) used for driving a magnetic head of a hard disk drive (HDD). This VCM is composed of a flat magnet, a back yoke, a yoke that supports the yoke, and a neodymium-iron-boron (Nd-Fe-B) rare earth magnet. The rare earth magnet weight used in the VCM has a certain width according to the thickness of the HDD. However, the weight corresponding to 1 to 2 g × 2 for 2.5 inch-HDD VCM and 2 to 10 g × 2 for 3.5 inch HDD is the standard rare earth magnet weight. Further, although the rare earth content in the VCM member greatly depends on the age of production, the neodymium content corresponds to about 26.0% in weight average, and the dysprosium content corresponds to about 1.6%. With regard to a technique for recovering rare earth elements from such rare earth magnet members, a recovery method with a low environmental load is desired.

The “rare earth magnet” is a magnet mainly composed of an intermetallic compound of rare earth metal and 3d transition metal such as iron (Fe) or cobalt (Co). Currently, the composition of rare earth magnets in practical use in Japan is as follows:
1. 2-14-1 type neodymium-iron-boron system represented by Nd ₂ Fe ₁₄ B 2. 1-5 type samarium-cobalt based on SmCo _{5 3.} Samarium-iron-nitride compound system represented by Sm ₂ Fe ₁₇ N ₃ 1-5 type praseodymium to the PrCo ₅ represented - there are four magnets that cobalt.
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 rare earth magnets. The term “iron group element” as used herein is a generic term for elements of groups 8, 9, and 10 of the fourth period on the periodic table, that is, three elements of iron (Fe), cobalt (Co), and nickel (Ni). It is. All of these iron group elements are 3d transition metals and are characterized by exhibiting ferromagnetism at normal temperature and normal pressure.

  Several techniques are known as techniques for recovering rare earth elements in the form of metals or ionic species from the rare earth magnets as described above. The methods are listed below.

First, there is a molten salt electrolysis method in which rare earth elements are recovered in the form of metal (see Patent Document 1).
The molten salt electrolysis method is a method in which an inorganic salt such as an alkali metal halide is brought into a high-temperature molten state and a compound containing a rare earth element is electrolytically deposited. Since the electrolytic bath temperature is high, there is an advantage that the rare earth oxide can be directly dissolved in the electrolytic bath. In the technique described in Patent Document 1, when performing molten salt electrolysis, the anode and 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 rare earth metal ions to the anode chamber, a voltage is applied between the anode and the cathode, and the rare earth metal is recovered 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, the rare earth element is concentrated by electrophoresis, and then the ionic liquid is added to the ionic liquid. On the other hand, there is a method of electrolytically removing a rare earth element after electrolytic removal of an iron group element (see Patent Document 2).

  The “ionic liquid” is a general term for ionic compounds having a melting point of 100 ° C. or less, which is a combination of a cation species and an anion species, and refers to a molten salt that forms a liquid phase at a temperature of 100 ° C. or less. . The vapor pressure of ionic liquids is very low and ionic liquids do not substantially generate harmful vapors. In addition, the ionic liquid exhibits hydrophobicity by appropriately selecting anionic species, and enhances the solubility of nonpolar substances due to the high polarity of the ionic liquid itself.

  Finally, there is a method 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 ionic species into an organic phase by distribution equilibrium in a state where an aqueous phase composed of an aqueous solution containing a rare earth element and an organic phase that is a hydrophobic ionic liquid are separated into two phases.

JP 2009-287119 A JP 2012-87329 A JP 2007-327085 A

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

  For example, in the molten salt electrolysis method such as Patent Document 1, an electrolytic bath based on neodymium fluoride-alkali metal fluoride may be used from a practical point of view in order to efficiently recover neodymium from rare earth magnets. Is appropriate. In this case, neodymium fluoride is a high melting point substance, and the electrolytic bath temperature needs to be set to an extremely high temperature of 1000 ° C. or higher. Therefore, it is necessary to design an apparatus that takes safety into consideration, such as an electrolytic apparatus that can suppress a corrosion reaction at a high temperature.

  In addition, ceramic materials that can withstand high temperature corrosion are generally expensive, requiring equipment costs, and increasing thermal energy.

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

  Next, in the technique described in Patent Document 2, a technique using an ionic liquid (for example, a water content of 50 ppm or less) is described. However, when a suitable iron removal process is not carried out in the VCM pretreatment process and the elution is performed directly, transition metal species (especially iron group elements) are mixed with rare earth elements in the ionic liquid. In this case, when the rare earth metal is finally electrodeposited, the electrochemically noble iron group element is inevitably reduced, so that the iron group element is co-deposited in the rare earth electrodeposits, resulting in high quality. It becomes difficult to recover the rare earth metal.

  Although it is possible to electrolytically recover the iron group element in advance, since the iron content in the rare earth magnet is large, the energy dose in the electrolytic deposition process is large. In addition, complication is brought about in the cooperative process of continuing the electrolytic recovery of the rare earth metal from the electrolytic recovery of the iron group metal. As a result, there is a significant point to be improved regarding the economic efficiency of the work process.

  Moreover, in the technique described in Patent Document 2, it is necessary to concentrate rare earth elements according to the rare earth concentration in the ionic liquid, and electrophoretic treatment must be performed. The electrophoresis process requires an applied voltage of about 30 to 50V. For this reason, the energy required for the electrophoresis process is enormous, and there is a great point to be improved regarding the economic efficiency in the work process.

  Finally, in the case of a solvent extraction method using a distribution equilibrium between an aqueous solution and an ionic liquid as represented by Patent Document 3, a rare earth element is efficiently extracted by using diglycolic anhydride as an extractant. it can. In addition, when the solvent extraction device has a multistage configuration, it is possible to concentrate rare earth species. However, in the solvent extraction method, the rare earth species are in the form of ionic species in any case, and in order to convert to a stable rare earth solid, it is necessary to form a precipitate in oxalate or carbonate. Furthermore, even when the rare earth species is recovered as an oxalate or carbonate, in order to change it to a metal form, it is necessary to electrolyze the rare earth salt in an electrolytic bath or to react with an active metal by thermal reduction. That is, when the solvent extraction method is applied alone, the biggest problem is that the rare earth species cannot be recovered in the form of metal.

As a problem newly found by the present inventor, there is an obstruction by boron for electrolytic recovery of rare earth elements. Boron is an element contained in a neodymium-iron-boron rare earth magnet with a composition ratio of Nd ₂ Fe ₁₄ B and an element whose content cannot be ignored. Boron is an electrochemically noble metal element, like the iron group element. Therefore, if boron is mixed with rare earth elements in the ionic liquid, the current efficiency at the time of electrolytic deposition is reduced because it is accompanied by eutectoid or adsorption with the rare earth elements during the final electrolytic deposition. Can be a factor. As a result, the present inventors have found a problem that it is difficult to electrolytically collect high-quality rare earth elements with the inclusion of boron.

  As described above, techniques for recovering rare earth elements from rare earth magnets are evolving day by day by many engineers, and the above improvements are also becoming apparent. If the above improvements can be overcome, it will lead to the establishment of a robust method for securing rare earth elements in the country, which will greatly contribute to the development of the industry.

  Accordingly, the main object of the present invention is to provide a rare earth element recovery method and a rare earth element recovery device using an ionic liquid that improve the quality of the recovered rare earth element while simplifying the work process. .

  In order to solve the above problems, the present inventor has intensively studied. In this earnest study, the present inventors paid attention to the technique described in Patent Document 2 as a technique for recovering a rare earth element from a rare earth magnet, using an ionic liquid and using electrolytic deposition.

  However, as described above, there is room for improvement in the technique described in Patent Document 2. And the inventor is composed of the above-mentioned points to be improved that iron group elements (and boron) are mixed together with rare earth elements, and anionic species that are common with anionic species derived from ionic liquids. Noted that a rare earth metal salt (ie low temperature melt) must be produced.

Therefore, the present inventor has obtained the following knowledge.
First, in accordance with “Electrodeposition method using ionic liquid” described in Patent Document 2, an iron group element, boron, and rare earth element contained in resources are converted into an acid solution derived from the anion species constituting the ionic liquid ( Elute to later aqueous phase solution).
Here, the present inventor applies the “solvent extraction method” that utilizes the characteristics of the hydrophobic ionic liquid to the pre-stage of the electrolytic deposition step after complying with the “electrolytic deposition method using an ionic liquid”. I came up with a completely new method. That is, in the “electrolytic deposition method using an ionic liquid”, a phase in which iron group elements, boron and rare earth elements are eluted with respect to the above acid solution, and a hydrophobic ionic liquid phase that has been applied in the electrolytic deposition process The present inventors have obtained a novel finding that a distribution equilibrium is established between the two and the present invention, which is suitable for performing the “solvent extraction method”.
Specifically, instead of removing iron group elements and boron from the above acid solution by precipitation separation or ion exchange resin, the above acid solution is positioned as an aqueous phase solution, and an organic phase solution composed of an ionic liquid is formed. By adding rare earth elements as ionic species as much as possible when extracting rare earth elements into ionic liquids by adding them ("organic phase solution" as used in this specification), unnecessary elements other than rare earth elements The inventors have come up with a method of remaining in the aqueous phase solution after the elution step.
In addition, as the organic phase solution, an electrolytic bath having a wide potential window on the reduction side and suitable for the electrolytic recovery of rare earth elements is selected. When the “solvent extraction method” is applied as a pre-process of the “electrolytic deposition method using an ionic liquid”, in an organic phase solution, an iron group element, boron, or other electrochemically is obtained by a precipitation separation method or the like. Rare earth species can be selectively distributed without mixing noble trace metal species. In addition, when a multi-stage extraction process is formed, the concentration of rare earth elements can be relatively increased to the extent that a salt generation process is not required in the subsequent process, and the organic phase solution itself is used for rare earth electrodeposition. The inventors have obtained the knowledge that the rare earth metal can be recovered as an electrolytic bath.
Thereafter, the organic phase solution needs to be configured by adding a solvating extractant to the ionic liquid as a diluent (solvent). Therefore, the expression “organic phase solution” is used instead of “solvent”. The conventional method called “solvent extraction method” is used as it is.
In this specification, the term “solvation extractant” means solvation extraction after the extractant forms a complex with a specific metal ion species in the aqueous phase in the distribution equilibrium between the aqueous phase and the organic phase. The extractant that can be extracted to the organic phase side by the mechanism is shown.

Aspects of the present invention based on the above findings are as follows.
The first aspect of the present invention is:
In the method for recovering rare earth elements using ionic liquid, the rare earth elements are recovered from resources containing iron group elements, boron and rare earth elements by electrolytic deposition of rare earth elements.
An elution step of eluting iron group elements, boron and rare earth elements from the resources into an aqueous phase solution;
Extraction that selectively extracts rare earth elements from the iron group elements, boron, and rare earth elements in the aqueous phase solution into an organic phase solution that can be used as an electrolytic bath for electrolytic deposition after the elution step. A separation process;
After the extraction and separation step, using the organic phase solution as an electrolytic bath, an electrolytic deposition step of electrolytically depositing a rare earth element from the organic phase solution;
A method for recovering a rare earth element using an ionic liquid, characterized by comprising:
However, the aqueous phase solution is an acid solution containing a hydrophobic anion species capable of constituting an ionic liquid, and the organic phase solution contains an ionic liquid and a solvating extractant.
A second aspect of the present invention is the aspect described in the first aspect,
The hydrophobic anionic species in the aqueous phase solution and the anionic species constituting the ionic liquid in the organic phase solution are the same type.
A third aspect of the present invention is the aspect described in the second aspect,
The hydrophobic anion species in the aqueous phase solution and the anion species constituting the ionic liquid in the organic phase solution can constitute an amide solution.
A fourth aspect of the present invention is the aspect according to any one of the first to third aspects,
A deironing step of separating the goethite from the aqueous phase solution by generating goethite as iron oxyhydroxide in the aqueous phase solution during the elution step and before the extraction and separation step. Furthermore, it is characterized by having.
A fifth aspect of the present invention is the aspect described in the fourth aspect,
In the extraction / separation step, the pH of the organic phase solution is more than 0.5 and not more than 5.0.
A sixth aspect of the present invention is the aspect described in the fourth or fifth aspect,
In the iron removal step, the goethite is precipitated by adding a hydroxide of an alkali metal element or alkaline earth metal element to the aqueous phase solution, and the goethite is separated from the aqueous phase solution,
The organic phase solution is a solution capable of selectively extracting a rare earth element from iron, boron and rare earth elements added with an alkali metal element or an alkaline earth element.
A seventh aspect of the present invention is the aspect described in any one of the first to third aspects,
In the extraction and separation step, the pH of the organic phase solution is 0.5 or less.
An eighth aspect of the present invention is the aspect according to any one of the first to seventh aspects,
In the extraction / separation step, when the ratio (A / O) of the volume (A) of the aqueous phase solution to the volume (O) of the organic phase solution is 1.0, the concentration of the solvating extractant is 1. 23M or more and 2.15M or less.
A ninth aspect of the present invention is the aspect according to any one of the first to seventh aspects,
In the extraction and separation step, when the concentration of the solvating extractant is 1.84 M, the ratio (A / O) of the volume (A) of the aqueous phase solution to the volume (O) of the organic phase solution is 0. 5 or more and 1.0 or less.
A tenth aspect of the present invention is the aspect described in any one of the first to ninth aspects,
The iron group element is at least iron.
An eleventh aspect of the present invention is the aspect according to any one of the first to tenth aspects,
The rare earth element recovered in the electrolytic deposition step is one or more selected from lanthanum element, cerium element, praseodymium element, neodymium element, samarium element, europium element, gadolinium element, terbium element and dysprosium element. It is an element.
The twelfth aspect of the present invention provides
In the rare earth element recovery device for recovering rare earth elements from resources containing iron group elements, boron and rare earth elements by electrolytic deposition of rare earth elements,
Organic phase that can be used as an electrolytic bath used for electrolytic deposition of rare earth elements among iron group elements, boron and rare earth elements in an aqueous phase solution in which iron group elements, boron and rare earth elements are eluted from the resources. A first processing section for selective extraction into a solution;
Using the organic phase solution as an electrolytic bath, and a second treatment part for electrolytically depositing rare earth elements;
A rare earth element recovery device using an ionic liquid.
However, the aqueous phase solution is an acid solution containing a hydrophobic anion species capable of constituting an ionic liquid, and the organic phase solution contains an ionic liquid and a solvating extractant.
The thirteenth aspect of the present invention provides
In the method for recovering rare earth elements using ionic liquid, the rare earth elements are recovered from resources containing iron, boron and rare earth elements by electrolytic deposition of rare earth elements.
An elution step of eluting iron, boron and rare earth elements from the resources into an aqueous phase solution;
Deironing to separate the goethite from the aqueous phase solution by adding a hydroxide of an alkali metal element or alkaline earth metal element to the aqueous phase solution to produce goethite that is iron oxyhydroxide. Process,
A positive extraction step of selectively extracting rare earth elements among boron and rare earth elements in the aqueous phase solution after the deironation step into an organic phase solution that can be used as an electrolytic bath used in electrolytic deposition; ,
After the normal extraction step, a back extraction step of selectively extracting the alkali metal element or alkaline earth metal element added in the iron removal step from the organic phase solution into a mineral acid that is dilute than an amide solution;
After the back extraction step, using the organic phase solution as an electrolytic bath, an electrolytic deposition step of electrolytically depositing a rare earth element from the organic phase solution;
A method for recovering a rare earth element using an ionic liquid, characterized by comprising:
However, the aqueous phase solution is an acid solution containing a hydrophobic anion species capable of constituting an ionic liquid, and the organic phase solution contains an ionic liquid and a diglycolamide type solvating extractant.
A fourteenth aspect of the present invention is the aspect according to the thirteenth aspect,
The hydroxide of the alkaline earth metal element added in the deironing step is calcium hydroxide, and the mineral acid used in the back extraction step is nitric acid.
A fifteenth aspect of the present invention is the aspect described in the fourteenth aspect,
A calcium hydroxide production step for producing calcium hydroxide by mixing alkali with nitric acid after the back extraction step;
Further comprising
In the iron removal step, the calcium hydroxide obtained in the calcium hydroxide production step and the aqueous phase solution are mixed to produce and precipitate goethite through the hydroxide, and then separated from the aqueous phase solution. It is characterized by doing.
A sixteenth aspect of the present invention is the aspect according to any one of the thirteenth to fifteenth aspects,
Before the electrolytic deposition step, a continuous extraction step of alternately repeating the normal extraction step and the reverse extraction step is provided.

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

3 is a flowchart showing a rare earth element recovery method in the first embodiment. It is a graph which shows the extraction rate of each metal ion seed | species according to pH of the organic phase solution after extraction with respect to the organic phase solution after extraction obtained in Example 1. FIG. 1 is a schematic view of a three-electrode electrolytic test apparatus used in this example. 10 is a flowchart showing a rare earth element recovery method according to the second embodiment. 2 is a graph showing the results of XPS analysis of the electrodeposit obtained in Example 1. It is a graph which shows the result of having analyzed XPS in the depth direction with respect to the deposit obtained in Example 1. FIG. It is a graph which shows the result of having analyzed XPS in the depth direction with respect to the deposit obtained in Example 2. FIG. 6 is a graph showing the relationship between TBP concentration and distribution ratio in extraction of each rare earth ion species in Example 3. 7 is a graph showing electrochemical behavior in an organic phase solution before extraction and an organic phase solution after extraction in Example 6 and an organic phase solution after extraction in Comparative Example 2. FIG. In Example 7, when the common anion species is [TFSA ⁻ ] or [FSA ⁻ ], each rare earth ion with respect to the concentration of the anion species for each rare earth ion species in the organic phase solution after the extraction separation step It is a graph which shows the correlation of a seed | species and a distribution ratio. (A) shows the result when the extraction target is Pr, (b) shows the result when the extraction target is Nd, and (c) shows the result when the extraction target is Dy. 10 is a flowchart illustrating a rare earth element recovery method according to Embodiment 3. In Example 8, it is a graph which shows the relationship of the distribution ratio of each metal seed | species with respect to the addition amount of TODGA (N, N, N ', N'-tetraoctyl diglycolamide). Is a graph showing the electrochemical behavior of the pre-extraction the organic phase solution _{TODGA / [P 2225] [TFSA} ] and third after stripping the organic phase _{TODGA / [P 2225] [TFSA} ] in Example 8. 10 is a graph showing the result of XPS analysis performed on the electrodeposit obtained in Example 9.

[Embodiment 1]
Hereinafter, embodiments of the present invention will be described in the following order with reference to FIG. FIG. 1 is a flowchart showing a rare earth element recovery method using an ionic liquid in the present embodiment. Hereinafter, it is simply referred to as “recovery method of rare earth element”.
1. Rare earth element recovery method 1-A) Disassembly / sorting process 1-B) Thermal demagnetization process 1-C) Plating stripping process 1-D) Oxidation roasting process 1-E) Elution process 1-F) Extraction separation process 1 -G) Electrochemical process 1-Ga) Anode dissolution process 1-Gb) First electrolytic deposition process 1-Gc) Second electrolytic deposition process 2. Rare earth element recovery equipment 3. Effects of the embodiment Modifications etc.
In addition, about the structure which is not described below, you may employ | adopt the structure as described in well-known literatures, such as patent document 2 (Unexamined-Japanese-Patent No. 2012-87329).
In the present embodiment, a method for recovering rare earth elements from real waste containing rare earth magnets, such as a voice coil motor (VCM), a drive motor for a hybrid vehicle, and a compressor for an air conditioner, and an apparatus therefor will be described. . Of course, the present invention can be applied to all cases where rare earth elements are recovered from resources in which iron group elements, boron and rare earth elements are mixed, even when rare earth elements are used in the form of magnets. is there.
In [Embodiment 2], which will be described later, an example in which the iron removal step is performed in advance before the extraction and separation step will be described.
In [Embodiment 3] to be described later, an example in which calcium is back-extracted from an organic phase solution to nitric acid after performing a deironing step and an extraction / separation step (forward extraction step) will be described.

<1. Rare earth element recovery method>
1-A) Dismantling / sorting step 1-D) Oxidation roasting step As pretreatment steps, 1-A) dismantling / sorting step, 1-B) thermal demagnetization step, 1-C) plating stripping step, 1- D) An oxidation roasting step, a pulverization step, and a classification step are performed. As a method, a known method may be adopted, and a specific method is as described in the embodiment.
In the enumeration below, in the dismantling / sorting step, the actual waste is dismantled / sorted. And the member as a rare earth magnet is collect | recovered from each member disassembled and separated.
In the thermal demagnetization step, the member as the rare earth magnet is heated to eliminate the residual magnetism of the member.
Next, when the plating layer is formed on the main surface of the member as the rare earth magnet, a plating peeling process is performed.
Then, the oxidation roasting process is performed to a certain weight increase rate (about 1.3 times before the oxidation treatment). The purpose of the oxidation roasting process is to suppress the amount of iron eluted from a member as a rare earth magnet in the elution process described later. In the elution step described later, iron is also eluted in the aqueous phase solution described later together with the rare earth element. However, the rare earth element can be selectively eluted by converting to the form of hematite (Fe ₂ O ₃ ) by performing the oxidation roasting step. As a result, the ratio of iron is reduced, and separation of iron and rare earth elements is facilitated.
Due to the oxidation roasting treatment, the particle size of the oxidized magnetic powder increases with sintering, so a pulverization step by an automatic mill is performed. The pulverized oxidized magnetic powder is classified using an automatic sieve until the particle size is 25 μm or less in the classification step. Oxidized magnetic powder having a particle size of 25 μm or less is used in the elution step described later.

1-E) Elution Step In the elution step, a resource containing an iron group element, boron and a rare earth element, which is a member as a rare earth magnet after the plating stripping step (hereinafter also simply referred to as “resource”). From at least iron group elements, boron and rare earth elements are eluted into the aqueous phase solution. In the present embodiment, “elution” in the elution step refers to ionizing at least iron group elements, boron, and rare earth elements with an aqueous phase solution. Of course, all the resources may be eluted into the aqueous phase solution.

  The aqueous phase solution used in the present embodiment is an acid solution containing a hydrophobic anion species that can form an ionic liquid. If it is an aqueous phase solution (acid solution) having a hydrophobic anionic species derived from this ionic liquid, it is possible to satisfactorily cause two-phase separation with respect to the organic phase solution described later. In other words, the rare earth elements to be collected are distributed to the organic phase solution as ionic species, and the aqueous phase solution contains electrochemically noble ionic species other than the rare earth elements that cause a reduction in current efficiency in the electrolytic deposition process. Remains.

As the aqueous phase solution, a known solution may be used as long as it satisfies the above conditions. For example, tetrafluoroboric acid _(HBF 4), hexafluorophosphate _(HPF 6), trifluoroacetic acid _(CF 3 COOH), methanesulfonic acid _(CH 3 _SO 3 H), trifluoromethanesulfonic acid _(CF 3 _SO 3 H ), Thiocyanic acid (HSCN) or the like may be used as the aqueous phase solution.

Mineral acids (inorganic acids such as nitric acid ([NO ₃ ⁻ ] of HNO ₃ ) and hydrochloric acid ([Cl ⁻ ] of HCl)) may be used as the acid component of the aqueous phase solution. For example, instead of eluting a resource directly with an acid solution comprising a hydrophobic anionic species capable of constituting an ionic liquid, the hydrophobic anionic species capable of constituting an ionic liquid is converted into a metal salt or after eluting the resource into a mineral acid. An “aqueous phase solution” may be prepared by adding an acid solution to the mineral acid solution after elution. That is, the “elution step” in the present specification is completed not only by eluting resources into the aqueous phase solution but also in a state where the hydrophobic anion species capable of forming the ionic liquid is present in the aqueous phase solution.

By the way, in this specification, “hydrophobic anion species” refers to a synthesis yield of 80% after removing impurities derived from precursors such as halogens when a ionic liquid is synthesized from a cation precursor and an anion precursor by a metathesis reaction. An anionic species capable of maintaining at least%.
In addition, [NO ₃ ⁻ ], which is an anion species of [P ₄₄₄₁₆ ] [NO ₃ ], [P ₆₆₆₁₄ ] [NO ₃ ] mentioned in <Comparative Example 1> described later, is a hydrophobic anion as used in this specification. Not included in seeds. Although [P ₄₄₄₁₆ ] [NO ₃ ], [P ₆₆₆₁₄ ] [NO ₃ ] have characteristics as an ionic liquid, the above synthesis yield is less than 80%. Furthermore, although [P ₄₄₄₁₆ ] [NO ₃ ], [P ₆₆₆₁₄ ] [NO ₃ ] are ionic liquids, they are not fully hydrophobic and part of the ionic liquid components become soluble in the aqueous phase. . Therefore, in this specification, [P ₃₄₁₆ ] [NO ₃ ], [P ₆₆₆₁₄ ] [NO ₃ ], which is an anionic species, [NO ₃ ⁻ ] is not a hydrophobic anionic species, so to speak, a semi-hydrophobic anionic species. is there.
In other words, the “hydrophobic anion species capable of forming an ionic liquid” is a hydrophobic anion species capable of forming an ionic salt when ionically bonded to a proton (H ⁺ ). However, even if it is a hydrophobic anion species, in this embodiment, resources are eluted in the aqueous phase solution to the last. That is, the ionic salt referred to here as an aqueous solution is an aqueous phase solution (acid solution) in this specification.

  However, instead of allowing the hydrophobic anion species to be present in the aqueous phase solution after eluting the resource into the mineral acid, an acid solution composed of a hydrophobic anion species capable of forming an ionic liquid, and the amide solution described below. Is preferably used as an aqueous phase solution from the viewpoint of recovery of rare earth elements. This is because acid solutions and amide solutions made of hydrophobic anionic species capable of forming an ionic liquid have higher rare earth leachability than mineral acids such as hydrochloric acid and nitric acid.

  By using the amide solution as the aqueous phase solution, while maintaining the high leachability of rare earth elements, iron group elements, boron and rare earth elements are relatively easily eluted out of the resources, and finally the rare earth elements are removed. It becomes possible to collect efficiently.

  In addition, the amide solution has an advantage that the elution of iron group elements is lower than that of rare earth elements. In that case, it becomes possible to perform the below-mentioned extraction separation process with respect to the aqueous phase solution in which the iron group element decreased, and finally the quality of the rare earth element can be improved.

  In the present specification, the “amide solution” refers to a solution that satisfies the conditions of the above aqueous phase solution and contains amide, and the amide solution is an anionic component of an ionic liquid typified by amic acid. It refers to the acid solution that has. The “amide” is a compound having a structure in which ammonia or a primary or secondary amine and an oxo acid are condensed by dehydration. Specifically, “amide” in the present specification includes carboxylic acid amide, sulfonamide, phosphoric acid amide and the like.

The amide solution may be any one as long as it can elute the iron group element, boron, and rare earth element. For example, acid compounds containing amides known as hydrophobic anion species of each compound described in Patent Document 2 and other ionic liquids may be mentioned. Specific names include bis (perfluoroalkylsulfonyl) amide (N [SO ₂ (CF ₂ ) _n CF ₃ ] ₂ ), bis (fluorosulfonyl) amide (N (SO ₂ F) ₂ ) (hereinafter, An amide solution containing “HFSA”), trifluoromethylsulfonylamide ((CF ₃ SO ₂ ) ₂ NH) (hereinafter also referred to as “HTFSA”), or the like may be used. “HTFSA” is also referred to as 1,1,1-trifluoro-N-[(trifluoromethyl) sulfonyl] methanesulfonamide.

  The resource eluted in the elution step may be in the form of any rare earth metal oxide, rare earth metal carbonate, rare earth metal or rare earth metal alloy. When the rare earth metal salt in the resource is a rare earth metal salt composed of a hydrophobic anion species having a weak cation-anion interaction, it can be easily eluted in an aqueous phase solution containing a hydrophobic anion species having a stronger interaction. Become.

  The elution method is not particularly limited as long as it is a method that allows iron group elements, boron, and rare earth elements to be efficiently eluted from the resources into the aqueous phase solution. As a specific example, the elution step may be performed by immersing the resource in an aqueous phase solution. Further, the pH may be adjusted by adjusting the concentration of the aqueous phase solution or adding an alkali or acid solution. By adjusting the pH, it is possible to control the rate at which the resource is eluted.

The aqueous phase solution is preferably in the state of an amide solution or the like containing a hydrophobic anion species capable of constituting an ionic liquid at the stage of the extraction / separation step described later. In other words, even if a mineral acid (for example, nitric acid) that is not a hydrophobic anionic species that can constitute an amide solution is eluted for the time being, the hydrophobicity that can constitute an ionic liquid in the solution after the elution A metal salt containing an anionic species (for example, Li [TFSA] or Li [FSA]) may be added. In addition, the organic phase solution may be a hydrophobic ionic liquid composed of a hydrophobic anionic species capable of constituting an amide solution such as [P ₂₂₂₅ ] [TFSA] or [P ₂₂₂₅ ] [FSA].
Even if the elution itself is performed using a relatively inexpensive mineral acid, the extraction rate of rare earth elements is dramatically improved by completing the above elution step by adding an appropriate amount of amide solution. It becomes possible. This example will be described later in <Example 7>.

  As another specific example, as described in Patent Document 2, by applying a voltage to a resource and dissolving it by anodic dissolution, iron group elements, boron and rare earth elements contained in the resource are converted into an aqueous phase solution. The method of making it melt | dissolve is mentioned.

1-F) Extraction and Separation Step One of the major features in this embodiment is the extraction and separation step. As described above, in this embodiment, in accordance with the “electrolytic deposition method using an ionic liquid”, a “solvent” that utilizes the characteristics of the hydrophobic ionic liquid in the previous stage of the electrolytic deposition step. "Extraction method" was applied. And in the post-process “electrolytic deposition using ionic liquid”, iron group elements, boron, electrochemically noble trace metals are removed, and the organic phase solution itself is used as an electrolytic bath for rare earth electrodeposition. It has reached a state where the rare earth metal can be recovered. Further, when the solvent extraction step is configured in multiple stages, a solution in which the concentration of the rare earth element is relatively increased to such an extent that a salt generation step is not required in the subsequent step is ready for use as an electrolytic bath.
More specifically, in this step, an organic phase solution that can be used as an electrolytic bath used for electrolytic deposition is added to the aqueous phase solution. Then, a rare earth element is extracted from the iron group element, boron, and rare earth element in the aqueous phase solution into the organic phase solution. You may perform a stirring process suitably.
In other words, while the iron group element and boron in the aqueous phase solution remain in the aqueous phase solution, the rare earth elements in the aqueous phase solution can be used as an electrolytic bath that can be used as an electrolytic bath for electrolytic deposition. Partition into solution as ionic species. The organic phase solution before extracting the rare earth element is referred to as “pre-extraction organic phase solution”, and the solution after extracting the rare earth element is also referred to as “post-extraction organic phase solution”.

The organic phase solution before extraction used here must satisfy the following conditions.
1. It contains an ionic liquid and a solvating extractant and becomes an organic phase solution with respect to the aqueous phase solution.
2. While the rare earth elements in the aqueous phase solution can be selectively extracted, the iron group elements and boron in the aqueous phase solution can remain in the aqueous phase solution.
3. It can be used as an electrolytic bath used for electrolytic deposition.
Of the above conditions, 2. And 3. Plays an extremely important role in the electrolytic deposition process described later. Especially 2. Greatly contributes to the improvement of current efficiency in the electrolytic deposition process.

  First, in the conventional “electrolytic deposition method using an ionic liquid” as described in Patent Document 2, a metal salt of a rare earth element is required before the electrochemical step. In order to obtain a metal salt of a rare earth element, it is necessary to remove the acid component by evaporating the acid component constituting the amide solution containing the rare earth element. In addition, the amide solution from which the acid component has been removed cannot be converted again into an amide solution capable of synthesizing the rare earth metal salt, and the amide solution required for the synthesis of the rare earth metal salt involves consumption.

  However, the pre-extraction organic phase solution in the present embodiment can be used as an electrolytic bath used for electrolytic deposition. Moreover, since the rare earth elements are selectively extracted into the organic phase solution after extraction, iron group elements other than rare earth elements, boron, and electrochemically noble trace metal species are not mixed into the organic phase solution after extraction. Furthermore, by adding an acid component such as amic acid to the aqueous phase solution, it can be used again as an acid solution that can be used in the elution process for rare earth leaching, and can be used repeatedly without discarding the acid solution. It becomes possible. Then, the electrolytic deposition process can be performed by thoroughly performing vacuum dehydration treatment on the organic phase solution after extraction after extracting the rare earth element. As a result, it is possible to omit a rare earth element metal salt production step by concentration of an ionic liquid using evaporation or the like, and the work process can be considerably simplified.

  Further, in the case where the rare earth element recovery process of the present embodiment is performed in a plurality of cycles, the organic phase solution after the extraction after the electrolytic deposition process is performed to deposit most of the rare earth element, It becomes possible to add to the electrolytic bath of the electrolytic deposition process in the cycle. That is, it becomes possible to reuse the organic phase solution after extraction.

  In addition, as described above, since the organic phase solution after extraction contains a relatively high concentration of rare earth elements, the quality of the rare earth elements finally obtained by the electrolytic deposition process can be improved. It becomes possible.

  And by using the organic phase solution which can selectively extract the rare earth element in an aqueous phase solution, there exists a great effect in the subsequent electrolytic deposition process.

  If a metal salt is generated from a solution in which iron group elements, boron and rare earth elements are eluted as in the prior art, not only iron group elements and boron but also other electrochemically noble elements are mixed in the metal salt. It will be. In that case, it is necessary to collect other electrochemically noble element groups in advance by preliminary electrolysis in the same manner as the iron group element and boron. If it is not recovered by preliminary electrolysis, there is a possibility that the quality of the rare earth metal to be recovered may be reduced due to eutectoid deposition in the electrolytic deposition process for recovering the rare earth element.

  However, as in this embodiment, in the “electrolytic deposition method using an ionic liquid”, the “solvent extraction method” is linked with the electrolytic deposition step to select and extract rare earth elements in the organic phase solution. It is possible to prevent other electrochemically noble elements from being distributed into the organic phase solution. In that case, adverse effects due to other electrochemically noble elements can be eliminated in the stage before the electrolytic deposition process.

  As used herein, “other electrochemically noble elements” include, for example, trace metal elements such as copper (Cu) and aluminum (Al). The “trace amount” here refers to a metal element of less than 1% by weight among the elements constituting the rare earth magnet.

  Other “other electrochemically base elements” include alkali metal elements appearing in [Embodiment 2] described later. The above-described effect is remarkable when an alkali metal hydroxide (for example, potassium hydroxide (KOH)) is used in performing the “deironation step” described in [Embodiment 2] described later. . This is because an organic phase solution having a property that potassium ions are difficult to be distributed during the extraction and separation step even if alkali metal (K) ions are present in the aqueous phase solution by performing a deironation step before this step. This is because it becomes possible to select. Details will be described later in [Embodiment 2]. Of course, an alkali metal hydroxide or alkaline earth metal hydroxide other than potassium hydroxide may be used.

  In addition, an organic phase solution is comprised by adding a solvation extractant with respect to the ionic liquid as a diluent (solvent).

なお、上記のオニウムカチオンの式の中の記号に当てはまる基の条件としては以下の通りである。
・Ｒは炭化水素基である。
・Ｒ^１は置換基を有していてもよい炭素数２〜６の直鎖状、分岐状、又は脂環状のアルキル基である。あるいはＲ^１はＲ’−Ｏ−（ＣＨ_２）_ｍ−で表されるアルコキシアルキル基（Ｒ’はメチル基またはエチル基を示し、ｍは１〜４の整数である）を示す。
・Ｒ^２は置換基を有していてもよい炭素数１〜１４の直鎖状、分岐状、又は脂環状のアルキル基である。
・複数のＲ^１はそれぞれ同じであっても異なっていてもよい。
・Ｒ^１とＲ^２とは互いに異なる基であり、ホスホニウムカチオンの有する炭素数の総数は２０以下である。
・Ｒ^３は置換基を有していてもよい炭素数２〜６の直鎖状、分岐状、又は脂環状のアルキル基である。
・Ｒ^４は置換基を有していてもよい炭素数１〜１４の直鎖状、分岐状、又は脂環状のアルキル基である。
・複数のＲ^３はそれぞれ同じであっても異なっていてもよい。
・Ｒ^３とＲ^４とは互いに異なる基であり、アンモニウムカチオンの有する炭素数の総数は２０以下である。
・ｎは０〜５の整数を表す。
・Ｒ^５は炭素数１〜５のアルキル基を示し、Ｒ^６はメチル基またはエチル基を示し、ｍ^＊は４または５の整数であり、ｎ^＊は１〜４の整数である。
なお、本明細書においては「〜」は所定の値以上且つ所定の値以下のことを指す。 As the ionic liquid, a known one may be used as long as it can be used as an organic phase solution and can be used as an electrolytic bath. As a specific example, the following may be used as the ionic liquid.
[Cationic component of quaternary phosphonium represented by formula PR ¹ R ¹ R ¹ R ² , cation component of quaternary ammonium represented by formula NR ³ R ³ R ³ R ⁴ or cation 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 dithiophosphoric acid ((RO) ₂ PSS)), aliphatic carboxylic acid (RCOO), hexafluorophosphate _(PF 6), Tetorafuruo Borate (BF ₄₎ and those composed of at least one anionic component selected from the group consisting of halogen or the like. ]

In addition, the conditions of the group applicable to the symbols in the above formula of the onium cation are as follows.
-R is a hydrocarbon group.
· R ¹ is a linear 2-6 carbon atoms which may have a substituent, branched, or alicyclic alkyl group. 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 is an integer of 1 to 4).
· R ² represents a linear Good 1 to 14 carbon atoms which may have a substituent, branched, or alicyclic alkyl group.
A plurality of R ¹ may be the same or different.
R ¹ and R ² are groups different from each other, and the total number of carbon atoms of the phosphonium cation is 20 or less.
· R ³ represents a linear 2-6 carbon atoms which may have a substituent, branched, or alicyclic alkyl group.
R ⁴ is a linear, branched, or alicyclic alkyl group having 1 to 14 carbon atoms that may have a substituent.
A plurality of R ³ 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 the integer of 0-5.
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, and n ^* is an integer of 1 to 4.
In the present specification, “to” refers to a value that is greater than or equal to a predetermined value and less than or equal to a predetermined value.

  In addition, you may use a well-known thing as a solvation extractant. Of course, the solvating extractant described in Patent Document 3 may be used, but the type is not limited as long as it is a solvating extractant having the above function. For example, it is preferable to use TBP (tri-n-butyl phosphate) from the viewpoint of efficiently extracting rare earth elements. The solvating extractant is also preferable because it has a higher solubility in the ionic liquid as the diluent than the acidic extractant and can increase the amount of metal loaded into the organic phase in the extraction system. Others include DBBP (di-n-butyl-n-butyl phosphate), TOP (tri-n-octyl phosphate), P-350 (dimethylheptylmethyl phosphate), CMPO (n-octyl (phenyl) -N, N It is also preferable to use -diisobutylcarbamoylmethyl) phosphine oxide, TOPO (trioctylphosphine oxide), TOA (tri-n-octylamine) or the like.

  In addition, it is preferable that the hydrophobic anion species constituting the acid in the aqueous phase solution and the anion species constituting the ionic liquid in the organic phase solution are the same. During the pre-equilibration of the extraction system, the anion species on the water phase side and the anion species on the organic phase side mutually dissolve and reach an equilibrium state. However, in the case of the same kind of anion species, the volume change at the time of mutual dissolution is small. This is desirable compared to the configuration of the anionic species.

When TBP is used in the solvation extractant, the solvation extraction mechanism of the ionic liquid system is expressed by the following extraction equilibrium equation. Here, the rare earth ions in the aqueous phase are coordinated to the unshared electron pair of the extractant and form a complex formation state of [RE (TBP) ₃ ³⁺ ]. In addition, in order to maintain electrical neutrality, both the anion species in the aqueous phase and the anion species constituting the ionic liquid are involved, and solvate formation (ion pair formation) results in [RE (TBP) ₃ ³⁺ ( TFSA) ₃ ] is stabilized with a solvated structure. [RE (TBP) ₃ ³⁺ (TFSA) ₃ ] is then formed in the aqueous phase and is distributed to the organic phase due to the hydrophobic nature of the complex. Here, the cation exchange [P ₂₂₂₅ ⁺ ] constituting the ionic liquid is simultaneously subjected to cation exchange extraction released to the aqueous phase side. That is, the ionic liquid extraction mechanism proceeds by both the solvation extraction mechanism and the cation exchange extraction mechanism, and a compound containing a rare earth element can be suitably formed.
[RE ³⁺ ] _aq ++ 3 [TBP] _org +2 [TFSA ⁻ ] _aq + [P ₂₂₂₅ ] [TFSA] _org
→ [RE (TBP) ₃ ³⁺ (TFSA) ₃ ] _org + [P ₂₂₂₅ ⁺ ] _aq
(RE = Rare earth element Pr, Nd, Dy, aq = aqueous phase, org = organic phase)
In the above extraction equilibrium equation, the hydrophobic anion species constituting the acid in the aqueous phase is [TFSA ⁻ ] _aq , and the anion species constituting the ionic liquid in the organic phase is [TFSA ⁻ ] _{org and the} same species. Thereafter, rare earth elements (RE) are recovered by direct electrodeposition from the extraction medium in an electrolytic deposition step described later. Elements other than rare earth elements (for example, iron group elements) have an electrostatic interaction with a solvating extractant or [TFSA ⁻ ] anion because the charge of the central metal ion is smaller than that of the rare earth element. It is not a constituent element of a compound formed in an aqueous phase because the interaction is weak and it is difficult to be accompanied by a complex formation state due to solvation. Moreover, in the above example, a common anion species derived from the amide solution is used in the aqueous phase solution and the organic phase solution. As a result, the quality of the collected rare earth element is naturally improved.

In the above solvation, the concentration of the hydrophobic anion species [TFSA ⁻ ] constituting the acid in the aqueous phase solution, the concentration of the ionic liquid in the organic phase solution, and the concentration of the solvating extractant (in this case [TBP]) are closely related. Is related to. Therefore, the above three concentrations are set so that the hydrophobic anion species constituting the acid in the aqueous phase solution and the anion species constituting the ionic liquid in the organic phase solution are the same species so as to cause solvation. Highly desirable.

In the extraction / separation step, which is this step, it is also important to set the pH of the organic phase solution when extracting rare earth elements. This will be described below.
As will be described in Examples below, in order to confirm whether or not the rare earth element has been properly extracted and whether or not the iron group element has not been extracted, the organic phase solution after the extraction is organically extracted. The extraction rate of each element according to the pH of the phase solution is examined. The result is shown in FIG.

From FIG. 2, it can be seen that the behavior of the extraction rate of the rare earth element and the iron group element changes greatly for each pH region.
Specifically, when the pH exceeds 0.5 and is 5.0 or less (preferably less than 5.0), the extraction rate of rare earth elements is at least 70% or more. Within that range, when the pH is 1.0 or more, the extraction rate of rare earth elements reaches 90% or more. On the other hand, with respect to iron group elements, the extraction rate can be limited to about 60%. That is, if the pH is in the above range, it is possible to extract the rare earth element efficiently from the pre-extraction organic phase solution. Moreover, since the extraction of rare earth species can be carried out in a wide pH range where the pH exceeds 0.5 and 5.0 or less, the range of application of the amide solution concentration in the elution process is expanded, and the rare earth composition ratio and elution amount to be eluted The elution process can be set according to the conditions. In addition, since it is possible to recover rare earth elements under relatively mild pH conditions, work safety is improved and maintenance of equipment for acid resistance is not required, and workability is dramatically improved. .

  On the other hand, when the pH is 0.5 or less, the extraction rate of the iron group element is almost zero%. Here, in the strongly acidic region, protonation of the extractant is involved, and the reduction of the amount of metal loaded on the organic phase in the extraction process is also a factor for lowering the extraction rate. And the extraction rate of rare earth elements maintains at least 60% or more. That is, if the pH is within the above range, the iron group element is hardly extracted into the organic phase solution before extraction. Then, when rare earth elements are finally electrolytically deposited, it becomes possible to recover rare earth elements of extremely high quality.

That is, the pH condition in the extraction / separation step may be set to one condition according to the effect desired to be acquired from the above two conditions.
When the pH exceeds 0.5 and is 5.0 or less, a particularly excellent effect is exhibited by performing the “iron removal step” described in [Embodiment 2]. Details will be described in [Embodiment 2].

  In the extraction / separation step, when the ratio (A / O) of the volume (A) of the aqueous phase solution to the volume (O) of the organic phase solution is 1.0, the concentration of the solvating extractant is 1.23 M or more. It is preferably 2.15M or less. As shown in <Example 3> to be described later, when the concentration of the solvating extractant is within the above range, it is possible to effectively extract rare earth species into an organic phase solution without containing Fe or B. It becomes.

  Furthermore, in the extraction / separation step, when the concentration of the solvating extractant is 1.84M, A / O is preferably 0.5 or more and 1.0 or less. As shown in <Example 4> to be described later, when the concentration of the solvating extractant is within the above range, it is possible to effectively extract rare earth species into an organic phase solution without containing Fe or B. It becomes.

1-G) Electrochemical process In the electrochemical process, an electrolytic treatment for recovering rare earth elements is performed. In this step, an electrolytic deposition step is performed in addition to the anodic dissolution step. This electrolytic deposition process is performed by changing conditions for each kind of rare earth element. This will be described below.

1-Ga) Anodic dissolution step In the anodic dissolution step, 1-F) an extracted organic phase solution after the extraction and separation step and containing a relatively high concentration of rare earth elements is electrolyzed. Use as a bath. In addition, about the specific method of this process, you may use the method of patent document 2, and a well-known method. Of course, an additional solution may be added to the organic phase solution after extraction, and a known ionic liquid may be used as the additional solution.

The above method will be briefly described with reference to FIG. In addition, FIG. 3 is the schematic for demonstrating the electrolytic test apparatus 1 used in the below-mentioned Example. In the present embodiment, a three-electrode electrolytic cell is used. Here, the demagnetized waste magnet member is attached to the anode part 2. And after making said organic phase solution after extraction into an electrolytic bath, the said anode part 2 is immersed in the organic phase solution (electrolytic bath) 14 after extraction with the cathode part 4. FIG. The reference electrode part 5 is also immersed in the organic phase solution (electrolytic bath) 14 after extraction. Then, the anode part 2 and the cathode part 4 are brought into conduction, anodic dissolution is performed, and the demagnetized waste magnet member is extracted and dissolved in the organic phase solution (electrolytic bath) 14. Here, the organic phase after the extraction of the anode portion 2 is not limited to the presence or absence of plating peeling of the waste magnet member, so that the iron or the plating component in the rare earth magnet component does not diffuse into the organic phase solution (electrolytic bath) 14 after the extraction. It is necessary to isolate it from the solution (electrolytic bath) 14 through the Vycor glass (glass filter 13). In addition, as the cathode part 4, you may use what rounded the copper plate to the substantially cylindrical shape like the below-mentioned Example, and uses the inert electrode which consists of the rare earth metal to precipitate and a metal element with a crystal structure similar. It doesn't matter.
Hereinafter, details will be described later in the embodiment, and the reference numerals are omitted.

1-Gb) First Electrolytic Deposition Step In the electrolytic deposition step, rare earth elements are electrolytically deposited from the low-temperature melt. And in the 1st electrolytic deposition process which is this process, neodymium (Nd) is deposited. As a specific method, the method of Patent Document 2 or a known method may be used. In addition, 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 as shown in Examples described later. However, there is no change in that rare earth elements are electrolytically deposited. In addition, in the present embodiment, it is possible to separate the iron group element, boron, and rare earth element, which have been a major factor in reducing the quality of the rare earth element.

  The above method will be briefly described. As the electrically connected anode part 2, an electrode made of the same kind of element as the rare earth element to be recovered (that is, Nd) or a demagnetized waste magnet member is used. As the cathode portion 4, a metal electrode that is electrochemically more noble than a rare earth element and has a crystal structure similar to the rare earth metal to be deposited is used. In addition, since the demagnetized waste magnet member can be used for the anode part 2, it is efficient to carry out the anodic dissolution process at the anode part 2 and the first electrolytic deposition process at the cathode part 4. It is.

1-Gc) Second electrolytic deposition step In the second electrolytic deposition step, which is this step, dysprosium (Dy) is deposited. About a concrete method, it is the same as that of a 1st electrolytic deposition process, and electrolytic deposition is performed on the conditions according to Dy.

  By the above method, a high-quality rare earth element is recovered (ie, the iron group element and boron are low in content and high purity) while removing the iron group element and boron from the resource.

<2. Rare earth element recovery equipment>
The above technical idea can be reflected in a rare earth element recovery apparatus. Specifically, the rare earth element recovery device in the present embodiment has the following configuration.
・ Organic phase that can be used as an electrolytic bath for the rare earth elements of iron group elements, boron and rare earth elements in an aqueous phase solution in which iron group elements, boron and rare earth elements are eluted from resources. First processing section (rare earth element extraction section) that selectively extracts into solution
・ Second treatment part (rare earth element electrolytic deposition treatment part) in which organic phase solution is used as electrolytic bath and rare earth elements are electrolytically deposited
In addition, about said 1st electrolytic deposition process and 2nd electrolytic deposition process, you may provide a separate process part like a 1st electrolytic deposition process part and a 2nd electrolytic deposition process part, Depending on the number of rare earth elements, third, fourth, etc. electrolytic deposition treatment units may be provided.

  The above configuration is <1. The same effect as the method described in the method of collecting rare earth elements> is achieved. That is, it is possible to improve the quality of the collected rare earth element by a relatively simple configuration of the first processing section (rare earth element extraction) and the second processing section (electrolytic deposition).

<3. Advantages of the embodiment>
According to this embodiment, the following effects can be obtained.

  First, the rare earth elements can be separated from the iron group elements and boron using a simple and efficient method of selectively extracting the rare earth elements into the organic phase solution before extraction, thereby improving the quality of the collected rare earth elements. It becomes possible. Moreover, as will be described later in the item of the example, the amount of rare earth elements recovered can be increased by the method described in the present embodiment. Furthermore, the purity of the collected rare earth element can be improved. In detail, even if the outermost surface of the collected rare earth element is oxidized or carbon is attached as an impurity, the portion other than the outermost surface (that is, the portion slightly deeper than the outermost surface) is relatively high. It becomes a rare earth element of purity, and finally it becomes possible to acquire a large amount of a rare earth element of high purity.

  And unlike the molten salt electrolysis method like patent document 1, the apparatus design which gave consideration of each step | paragraph to the safety | security aspect, such as the electrolysis apparatus which can suppress the corrosion reaction at high temperature, becomes unnecessary. As a result, equipment costs can be reduced and less energy (heat and electrolysis) needs to be added.

  Further, unlike Patent Document 2, it is not necessary to separately deposit an iron group element, and an increase in the number of electrolytic deposition steps can be suppressed. In addition, by using a post-extraction organic phase solution containing a relatively high concentration of rare earth elements as an electrolytic bath, the constituent ratio of the rare earth elements in the aqueous phase solution can be relatively increased as compared with conventional recovery methods. Can do. This eliminates the need for performing an electrophoresis process for the purpose of enriching rare earth elements. As a result, economic efficiency in the work process can be improved.

  Above all, the use of an organic phase solution capable of selectively extracting rare earth elements in the aqueous phase solution has a great effect in the subsequent electrolytic deposition step. That is, by applying the “solvent extraction method” utilizing the characteristics of the hydrophobic ionic liquid to the previous step of the “electrolytic deposition method using an ionic liquid” as in this embodiment, the organic phase solution contains It becomes possible to select and extract rare earth elements. It is also possible to prevent iron group elements, boron and other electrochemically noble elements from entering the organic phase solution. Therefore, it is possible to overcome the factor of the decrease in current efficiency at the time of electrolytic deposition due to other electrochemically noble elements in the previous stage of the electrolytic deposition process.

  Furthermore, the pre-extraction organic phase solution in the present embodiment can be used as an electrolytic bath used for electrolytic deposition. In addition, since the rare earth element is selectively extracted into the organic phase solution before extraction, the concentration of the rare earth element is already relatively high. That is, using the organic phase solution after extraction after extracting the rare earth element, the electrolytic deposition step can be performed as it is. As a result, the step of synthesizing the rare earth metal salt, the step of eluting the salt into the ionic liquid, and the dehydration step can be omitted, and the work process can be considerably simplified.

  Further, in the case where the rare earth element recovery process of the present embodiment is performed in a plurality of cycles, the organic phase solution after the extraction after the electrolytic deposition process is performed to deposit most of the rare earth element, It becomes possible to add to the electrolytic bath of the electrolytic deposition process in the cycle. That is, it becomes possible to reuse the organic phase solution after extraction.

  In addition, as described above, since the organic phase solution after extraction contains a relatively high concentration of rare earth elements, the quality of the rare earth elements finally obtained by the electrolytic deposition process can be improved. It becomes possible.

  In addition, after applying the “solvent extraction method” utilizing the characteristics of the hydrophobic ionic liquid in the previous stage of the process after conforming to the “electrolytic deposition method using an ionic liquid” as in the present embodiment, By linking to the `` electrolytic deposition method '', the solvent extraction process also serves as a deironing process, eliminating the need to separately deposit iron group elements and minimizing the energy dose required for the electrolytic deposition process It becomes possible to do. As a result, economic efficiency in the work process can be improved.

  As described above, the quality of the collected rare earth element can be improved while simplifying the work process.

<4. Modified example>
The technical scope of the present invention is not limited to the above-described embodiments, and includes various modifications and improvements as long as the specific effects obtained by the constituent elements of the invention and combinations thereof can be derived.

(Rare earth element types)
In the above embodiment, the type of element in the rare earth element is not limited. However, in consideration of practicality and ease of work, lanthanum element (La), cerium element (Ce), praseodymium element (Pr), One or more elements selected from neodymium element (Nd), samarium element (Sm), europium element (Eu), gadolinium element (Gd), terbium element (Tb) and dysprosium element (Dy) Is preferred.

(Omission of elution process)
In the above embodiment, the elution step was performed. On the other hand, if a solution prepared by eluting resources in the aqueous phase solution is prepared separately, the elution step may be omitted. Hereinafter, a method for collecting a rare earth element using an ionic liquid when the elution step is omitted will be described.
In the method of recovering rare earth elements using ionic liquid, recovering rare earth elements from resources containing iron group elements, boron and rare earth elements by electrolytic deposition of rare earth elements,
Among the iron group elements, boron and rare earth elements in the aqueous phase solution from which the iron group elements, boron and rare earth elements have been eluted from the resources, the rare earth elements can be used as an electrolytic bath used for electrolytic deposition. An extraction separation step for selective extraction into an organic phase solution;
After the extraction and separation step, using the organic phase solution as an electrolytic bath, an electrolytic deposition step of electrolytically depositing a rare earth element from the organic phase solution;
A method for recovering a rare earth element using an ionic liquid, comprising:
However, the aqueous phase solution is an acid solution containing a hydrophobic anion species capable of constituting an ionic liquid, and the organic phase solution contains an ionic liquid and a solvating extractant. ]

  Note that “selective extraction” in the present specification refers to, for example, first extracting a predetermined element from each element in the aqueous phase solution. However, even if it is selective extraction, it is assumed that other elements are inevitably extracted, but that does not mean that the other elements are selectively extracted. Even if it extracts, it does not change that a predetermined element is mainly extracted.

[Embodiment 2]
[Embodiment 1] which is the above embodiment uses a technique of extracting rare earth elements into an organic phase solution before extraction that can be used as an electrolytic bath, instead of removing iron group elements. On the other hand, the present invention does not exclude the combination of “extraction of rare earth elements” and “removal of iron group elements”. Rather, the effect of the present invention can be remarkably increased by combining both. Specifically, in the present embodiment, the following steps are included in the rare earth element recovery method.
・ Deironation step of separating the compound from the aqueous phase solution by generating a compound containing an iron group element in the aqueous phase solution between the elution step and before the extraction and separation step.

Hereinafter, the iron removal process will be described with a focus. Hereinafter, the present embodiment will be described in the following order with reference to FIG. FIG. 4 is a flowchart showing a rare earth element recovery method in the present embodiment.
In the following example, the case where an iron group compound forms goethite (FeOOH) which is iron oxyhydroxide via [Fe (OH) _x ] ^3-x, for example, iron (III) hydroxide will be described. In addition, <1. The description of the method for recovering rare earth elements is as follows. The process marked with * is a newly added process.
1. Rare earth element recovery method 1-A) Disassembly / sorting process 1-B) Thermal demagnetization process 1-C) Plating stripping process 1-D) Oxidation roasting process 1-E) Elution process * 1-F) Deironing process * 1-Fa) Oxidation process * 1-Fb) Precipitation titration process 1-G) Extraction separation process 1-H) Electrochemical process 1-Ha) Anode dissolution process 1-Hb) No. One Electrolytic Deposition Step 1-Hc) Second Electrolytic Deposition Step In the following description, the description will be made based on the above description (for example, 1-F) iron removal step). Note that matters not described below are the same as those in [Embodiment 1], or known techniques may be used.

  The “elution” in the above elution step means that the iron group element can be changed into a compound (such as FeOOH which is goethite) while at least the rare earth element is ionized by the aqueous phase solution. It refers to ionizing an element with an aqueous phase solution.

1-F) Deironing step In this embodiment, a strong acid (for example, concentrated nitric acid) having higher oxidizing power than the acid component in the aqueous phase solution is used for the aqueous phase solution from which the iron group element, boron and rare earth element are eluted. Used to add the amount necessary to oxidize the iron group ionic species from divalent to trivalent. Thereby, the process which precipitates only an iron group element as a hydroxide is performed, without precipitation of rare earth hydroxide. Note that the amount of strong acid required to oxidize the iron group ion species from divalent to trivalent is increased by about 2 ml from the stoichiometric amount, or 1.2% from the content of iron group ion species. When the amount more than double is added, the oxidation treatment proceeds efficiently.

  Further, in this step, an iron group element is formed using at least one of an alkali metal hydroxide aqueous solution, an alkaline earth metal hydroxide aqueous solution, an ammonia aqueous solution, a rare earth hydroxide aqueous solution, and a mixture thereof. A hydroxide is preferred. These aqueous solutions may be used as a titrant (precipitation forming agent). With these aqueous solutions, goethite can be precipitated relatively easily, and the pH can be easily adjusted. Moreover, even when sodium hydroxide is used as the aqueous hydroxide solution containing metal or when potassium hydroxide is used, the organic phase solution sets a substance that is difficult to extract sodium or potassium as the organic phase solution, It is possible to electrolytically deposit extremely high-quality rare earth elements.

  Further, a mixture of alkali metal hydroxides, a mixture of alkali metal hydroxide and rare earth hydroxide, or a mixture of ammonium and rare earth hydroxide may be used as a precipitation forming agent for the precipitation of iron group elements. Absent.

  In this embodiment and [Embodiment 1], the iron group element is not particularly limited. In the present embodiment, the case where the iron group element is Fe will be described, but it goes without saying that an iron group element other than Fe may be included. That is, in this embodiment, the case where at least Fe is contained as an iron group element is described. In addition, the iron group element indicates three types of Fe, Co, and Ni, but when a magnetic member that is insufficiently stripped of Ni that is a plating component of the waste rare earth magnet is eluted into the aqueous phase solution, When both ionic species of Fe and Ni are contained in the aqueous phase solution, only the Fe ions are rapidly oxidized to trivalent by administration of the oxidizing agent. In addition, only trivalent iron hydroxide can be selectively precipitated and separated by appropriately adjusting the pH after using the above-described precipitation forming agent. The remaining Ni ions can be removed relatively easily by performing constant potential electrolysis in an aqueous solution. Alternatively, by setting a substance that does not extract Ni from the organic phase solution as the organic phase solution, it becomes possible to electrolytically deposit rare earth elements of extremely high quality.

1-Fa) Oxidation treatment step When the iron group element is Fe, it is necessary to add an oxidizing agent to the aqueous phase solution. That is, it is necessary to perform an oxidizing agent administration step separately. Further, in the elution treatment of Fe into the aqueous phase solution, Fe in the resource is eluted as a divalent metal ion. On the other hand, the pH region in which divalent Fe ions form a hydroxide to form a precipitate has a large range overlapping the pH region in which a rare earth element forms a hydroxide to form a precipitate. This means that the divalent Fe 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 addition, as an oxidizing agent, the mineral acid whose oxidizing power is stronger than the acid which comprises said aqueous phase solution is desirable. An example of this mineral acid is concentrated nitric acid. When concentrated nitric acid is used, it is converted to trivalent Fe ions by the following reaction.
Fe ²⁺ + 2HNO ₃ → Fe ³⁺ + NO ₃ ⁻ + NO ₂ + H ₂ O
The above reaction proceeds relatively slowly, and it is desirable to set the reaction temperature to 70 to 90 ° C. and the reaction time to 7 hours or longer. In addition, Fe ions may be oxidized from divalent to trivalent by bubbling with ozone or chlorine, or other known oxidation methods may be used. Further, the dose of the oxidizing agent is preferably 1.2 times or more than the Fe ion content. In some cases, heating may be performed. This ensures that the total amount of Fe in the aqueous phase solution is oxidized to trivalent ions.

1-Fb) Precipitation titration step In the case of this embodiment, for example, an aqueous NaOH solution is used as a precipitation forming agent. In the precipitation titration step, when the iron group element is Fe, goethite is precipitated and separated by using an aqueous solution of an alkali metal hydroxide as a precipitation-forming agent after administration of the oxidizing agent. The precipitation end point pH may be any pH as long as Fe in the ionic liquid changes to goethite when NaOH aqueous solution is added. However, when the pH is close to the acidic side, Fe tends to remain in the solution, and when the pH is close to the neutral side, rare earth coprecipitation tends to occur. In view of this, when the precipitation forming agent is an alkali metal, and particularly NaOH, the preferable pH for the precipitation formation is 3.8 or more and 4.7 or less.

  By the way, as described in [Embodiment 1], in the extraction / separation step performed after the precipitation titration step, the extraction rates of rare earth elements and iron vary greatly depending on pH conditions. And in this embodiment, when “pH exceeds 0.5 and 5.0 or less” among the pH conditions described above, it is possible to double the effects brought about by this embodiment.

Again, in the precipitation titration step, the preferred end point of precipitation is 3.8 or more and 4.7 or less, partially overlapping with the pH range of “pH> 0.5 and 5.0”. . More specifically, it overlaps when the pH is between 3.8 and 4.7. This means that the aqueous phase solution after sufficiently removing iron by the precipitation titration step can be transferred to the extraction / separation step without having to change the pH of the aqueous phase solution. As a result, the work can be greatly simplified. Moreover, as described above, in the pH range of “pH exceeds 0.5 and 5.0 or less”, the extraction rate of rare earth elements is at least 70% or more. Within that range, when the pH is 1.0 or more, the extraction rate of rare earth elements reaches 90% or more. Moreover, in the present embodiment, the iron in the aqueous phase solution is removed in advance by performing the “deironation step”. For this reason, it is possible to prevent extraction of iron into the organic phase solution before extraction with an extremely high extraction rate of rare earth elements. By doing so, it is possible to improve the amount of rare earth element recovered while enjoying the effect due to the mild pH described above. Moreover, in addition to the above-described configuration, when the solvation is caused by the same type of the hydrophobic anion species constituting the acid in the aqueous phase solution and the anion species constituting the ionic liquid in the organic phase solution, the workability is remarkably improved. However, it is possible to recover rare earth elements with extremely high purity.

  In the case where the rare earth species is efficiently extracted in a pH region (1.0 to less than 3.8) that does not overlap after the iron removal treatment, the aqueous phase solution after the iron removal treatment is changed to an Na-substituted ion exchange resin. A treatment for soaking is required. In this case, by replacing Na ions and protons, the pH of the aqueous phase solution can be shifted to the acidic side with respect to the pH at the time of precipitation formation while Na ions in the aqueous phase solution are somewhat reduced. In this way, by controlling the pH from the substitution amount of Na ions and protons, the rare earth species is maintained in a state where the extraction rate is maintained at about 90% in a non-overlapping pH region (1.0 to less than 3.8). Can be efficiently distributed to the organic phase solution.

Hereinafter, preferred examples and modifications of the present embodiment will be described.
In this embodiment, 1-F) the deironing step was performed after 1-E) the elution step and before 1-G) the extraction separation step. On the other hand, an iron removal step may be performed during the elution step. This will be described below.

  As described in [Embodiment 1], a case where a hydrophobic anion species capable of forming an ionic liquid is added to the solution after the elution after the resource is eluted in the mineral acid is also included in the present invention. In this case, the iron removal step may be performed “after the resource is eluted with the mineral acid” and “before the hydrophobic anion species capable of forming the ionic liquid is added”.

  As described above, the “elution step” in this specification not only elutes the resources in the aqueous phase solution, but also in a state where the hydrophobic anion species capable of forming the ionic liquid is present in the aqueous phase solution. Will be completed. That is, in the above case, the iron removal step is performed before the elution step has not yet been completed. As a result, in the above example, “the iron removal process is performed during the elution process”. In other words, at least the aqueous phase solution subjected to the extraction / separation step is in a state containing a hydrophobic anion species capable of forming an ionic liquid.

  Moreover, it is preferable to make the aqueous phase solution in an elution process into the temperature conditions of the range of 80-90 degreeC. The reason is that the elution reaction rate is increased and the elution degree of iron oxide is kept low without accompanying evaporation of the aqueous phase solution.

  In addition, when performing the iron removal process by a precipitation titration process as a metal concentration in an aqueous phase solution, it is preferable to set it as 0.5M-1.0M. The reason is that the amount of the rare earth component eluted in the magnet member is high, and in the subsequent precipitation titration step, the amount of precipitation forming agent added is not increased by the end point. In other words, when the metal concentration of the aqueous phase solution is too high, the amount of precipitation of the precipitation-forming agent increases and the content of the rare earth component is prevented from decreasing. On the other hand, the metal concentration in the aqueous phase solution is preferably 1.5M to 2.0M in the case of performing the iron removal treatment not by the precipitation titration step but by the extraction separation step. The reason for this is that rare earth ion species can be distributed without distributing Fe ions to the organic phase solution side by extraction and separation in the region of pH 0.5 or less.

  The reaction time is preferably 9h to 12h. The reason is that the magnet member after the oxidative roasting treatment is a hardly soluble rare earth oxide, and the elution process requires a time of 9 hours or more, and when a long time reaction exceeding 12 hours is performed, This is because the elution amount of the group oxide increases and is suppressed. When the oxidized and roasted magnetic powder is micronized to 30 μm or less and the weight ratio of the oxidized magnetic powder fine powder (g) to the aqueous phase solution (L) is 10.0, the reaction time is 7 h. Is preferred.

In the present embodiment, an example in which iron (Fe ³⁺ ) among iron group elements is changed to hydroxide is described. On the other hand, as long as a compound containing an iron group element in the aqueous phase solution is produced and the compound can be separated from the aqueous phase solution, it does not have to be changed to a hydroxide. As a specific example, an iron group element may be converted into an oxide, a sulfonated product or an iron group complex salt to generate a compound containing the iron group element, and the compound may be separated.

In addition, the solid compound may not be precipitated, or may be in a floating state in the liquid. In that case, it becomes possible to solid-liquid separate the compound containing the iron group element and the aqueous phase solution containing the rare earth element by a known technique such as filtration or centrifugation. That is, the above-mentioned “deironation step” is one specific example, and is included in the “deironation step” in which a compound containing an iron group element in the aqueous phase solution is generated to separate the compound.
Even if the compound to be produced is a liquid, the compound can be separated from the aqueous phase solution using phase separation or the like. However, considering the ease of separation from the aqueous phase solution, the compound is preferably a solid. That is, it is preferable to solid-liquid separate the compound from the aqueous phase solution.

  In addition, in order to clarify that the description described in this specification is different from the “technology for separating iron group elements by electrolytic deposition” as described in Patent Document 2, in the iron removal process, The expression “produces hydroxide from iron ions (III) in solution” is used. On the other hand, the expression “rare earth element electrolytic deposition” is used in the electrolytic deposition process described later. That is, in the deironation process, a chemical reaction that does not involve redox occurs, ie, a bond between iron group element ions and other ions. On the other hand, in the electrolytic deposition process, metal deposition accompanied by oxidation / reduction in which ions of rare earth elements become zero-valent occurs.

As can be said for [Embodiment 1], the iron group element is not particularly limited in this embodiment. In the present embodiment, the case where the iron group element is Fe will be described, but it goes without saying that iron group elements (Co, Ni) other than Fe may be included. For example, you may perform the process corresponding to said iron removal process with respect to another iron group element (Co, Ni) instead of Fe.
Therefore, when the “deironation step” is regarded as a larger concept, it can be referred to as an “iron group compound separation step”.

In addition, the following configuration may be added as a rare earth element recovery device.
-A goethite separation unit for separating goethite from an aqueous phase solution by generating goethite from an aqueous phase solution in which iron and rare earth elements are eluted from resources.

  According to this embodiment, in addition to the effects of [Embodiment 1], the following effects are obtained.

  First, since iron can be removed by a simple and efficient method of precipitation separation, it is possible to improve the quality of recovered rare earth elements. Moreover, as will be described later in the item of the example, the amount of rare earth elements recovered can be increased by the method described in the present embodiment. Furthermore, the purity of the collected rare earth element can be improved. Specifically, even if the outermost surface of the collected rare earth element electrodeposits is oxidized or carbon is mixed as an impurity, the portion other than the outermost surface (that is, the portion slightly deeper than the outermost surface) has a relatively high purity. It is possible to obtain a large amount of high-purity rare earth elements in the end.

  And unlike the molten salt electrolysis method like patent document 1, the apparatus design which gave consideration of each step | paragraph to the safety | security aspect, such as the electrolysis apparatus which can suppress the corrosion reaction at high temperature, becomes unnecessary. As a result, equipment costs can be reduced and less energy (heat and electrolysis) needs to be added.

  Further, unlike Patent Document 2, it is not necessary to separately deposit an iron group element (mainly Fe), which occupies a high proportion in the magnet member, so that the electrolytic energy required for the electrolytic deposition process can be significantly suppressed. It becomes possible. Moreover, the composition ratio of the rare earth elements in the aqueous phase solution can be relatively increased by separating the goethite by precipitation as compared with the conventional recovery method. This eliminates the need for performing an electrophoresis process for the purpose of enriching rare earth elements. In addition, the electrical energy required for the electrophoresis process can be greatly suppressed. As a result, the economics of energy dosage in the recovery process can be improved as a whole process.

  Further, unlike the solvent extraction method such as Patent Document 3, since the extraction and separation process is not applied alone but is linked to the electrolytic deposition process, the rare earth component in the magnet member is not an ionic species but a metal. It can be efficiently recovered in the form. Further, it is not necessary to separately deposit iron, and the electrolytic energy required for the electrolytic deposition process can be suppressed. As a result, the economic efficiency in the rare earth species recovery process can be improved.

  Further, by appropriately adjusting the pH of the aqueous phase solution in the elution step, it is possible to directly connect to the extraction / separation step without the need to particularly change the pH of the aqueous phase solution after sufficiently removing iron by the precipitation titration step. As a result, the work can be greatly simplified. Moreover, since the iron has been removed in advance, the extraction rate of the rare earth element is extremely high by setting the pH range of “pH is over 0.5 and 5.0 or less”, and then into the organic phase solution before extraction. Iron is not extracted and can be completely separated. By configuring in this way, it is possible to greatly improve the amount of rare earth element recovered while enjoying the effects due to the mild pH described above. Moreover, in addition to the above-described configuration, when the solvation is caused by the same type of the hydrophobic anion species constituting the acid in the aqueous phase solution and the anion species constituting the ionic liquid in the organic phase solution, the workability is remarkably improved. However, it is possible to recover rare earth elements with extremely high purity.

  As described above, by precipitating and separating iron in advance, it is possible to greatly improve the quality of the collected rare earth element while simplifying the work process.

(Comparison with the prior invention conceived by the present inventor)
The present inventor, in addition to the present invention, in the “electrolytic deposition method using an ionic liquid”, an invention that uses a “iron removal step” without cooperation with the “solvent extraction method” (hereinafter referred to as “prior invention”). ")" (Japanese Patent Application No. 2012-234202). Naturally, the prior application invention is not disclosed at the time of filing of the present invention, and is not a prior art.

  In the prior invention, as in the present invention, it is an object that iron is contained in the recovery of rare earth elements. And in order to solve the subject, after elution of iron and rare earth elements to an amide solution, the iron removal process is performed before the electrolytic deposition process. Therefore, the invention of the prior application also has an effect of improving the quality of the collected rare earth element while simplifying the work process.

  Certainly, in the deironing step, selective separation is possible because precipitation conditions (pH at which precipitation is formed) differ between iron and rare earth elements. However, an alkali metal hydroxide or the like is necessarily required as a precipitation forming agent. If the Fe concentration is high, a large amount of alkali metal hydroxide is required. In that case, in the amide solution, the concentration of the alkali metal element increases and the proportion of rare earth ions decreases. In the invention of the prior application, after the iron removal step, the amide solution is concentrated to perform a salt generation step for generating a low-temperature melt containing a rare earth element. Thus, when using a low-temperature melt as an electrolytic bath, it is important to maintain the electrolysis conditions in which the alkali metal element is not deposited in the electrolytic deposition step, but when the alkali metal is co-deposited in the electrodeposit, It may also reduce the quality of rare earth elements.

  Here, as a result of studying the above contents, the present inventor has renewed the idea and improved the quality of rare earth elements, whether or not a deironing process is introduced after the elution process. I came up with a method to simplify the work. That is the linkage between the “solvent extraction method” and the “electrolytic deposition method”.

  By using this technique, not only iron, but also boron, trace metals, and alkali metal elements or alkaline earth metal elements that are always administered in the iron removal process are not mixed into the organic phase solution, and rare earth elements can be added. It becomes possible to partition into the organic phase solution. By this method, the effect of the present invention can be achieved when the deironing process is not used, and even when the deironing process is used, the quality of the rare earth element is improved by mixing a large amount of alkali metal elements or alkaline earth metal elements. Can be eliminated, and only the merit of using the iron removal process can be enjoyed. Furthermore, to reiterate, when the “solvent extraction method” and the “electrolytic deposition method” are linked, the concentration of the rare earth element in the organic phase solution becomes so high that the salt generation step is not required later. In addition, the solution containing the rare earth element itself can be used as it is as an electrolytic bath. As a result, not only the quality of the recovered rare earth element is remarkably improved, but also a remarkable effect is obtained that a salt generation step is not required.

In addition, in accordance with the idea of the above method, the rare earth extraction rate is achieved by using an ionic liquid as a diluent in the organic phase solution and using the anionic species of the ionic liquid and the hydrophobic anionic species on the acidic aqueous phase side as a common anion. The present inventor has also found out that
By utilizing the characteristics of this common anion, even in the case where iron is precipitated and separated using an alkali metal as a precipitation-forming agent in the pre-stage of the extraction and separation process, the rare earth is in a wide range of 0.5 <pH ≦ 5.0. The present inventor has also found that the extraction and separation step can be applied under the condition of element extraction rate: 90% or more.
Furthermore, an extraction-electrolysis cooperative method in which a rare earth element can be electrolytically reduced and recovered in the form of a metal by using the organic phase extracted from the rare earth species in the extraction and separation process as an electrolytic bath in the electrolytic deposition process. The inventor has conceived.

  That is, the present inventor has devised an invention that has an advantageous effect that exceeds not only the known prior art but also the prior invention that has not yet been disclosed. And the application regarding the above content is this application.

[Embodiment 3]
In this embodiment, the steps up to 1-F) deironation and 1-G) extraction and separation in [Embodiment 2] are performed to obtain an organic phase solution containing a rare earth element. Then, the alkali metal element or alkaline earth metal element derived from the alkali metal or alkaline earth metal hydroxide used in the iron removal step is separated from the organic phase solution.

Hereinafter, the present embodiment will be described in the following order with reference to FIG. FIG. 11 is a flowchart showing a rare earth element recovery method in the present embodiment.
In addition, <1. The description of the method for recovering rare earth elements is as follows. Note that the process marked with * is a process newly added or changed in content as compared with [Embodiment 2].
1. Rare earth element recovery method 1-A) Disassembly / sorting process 1-B) Thermal demagnetization process 1-C) Plating stripping process 1-D) Oxidation roasting process 1-E) Elution process * 1-F) Deironing process * 1-Ga) Positive extraction process (corresponds to extraction separation process)
* 1-Gb) Back extraction process * 1-Gc) Continuous extraction process (alternate repetition of normal extraction process and back extraction process)
1-H) Electrochemical process 1-Ha) Anode dissolution process 1-Hb) First electrolytic deposition process 1-Hc) Second electrolytic deposition process For matters not described below The same as [Embodiment 1], or a known technique may be used.

1-F) Deironing Step The purpose of this step (hereinafter also referred to as “deironing step”) is the same as in [Embodiment 2]. However, in this step, a method having no environmental load such as oxygen bubbling is used as the oxidation treatment step. As a result, a treatment is performed in which only iron ions (III) are converted into hydroxides and finally precipitated as goethite without causing precipitation of divalent iron hydroxide (II) or rare earth hydroxide.

  In addition, Fe ions may be oxidized from divalent to trivalent by bubbling with ozone having strong oxidizing power, or other known oxidation methods may be used. This ensures that the total amount of Fe in the aqueous phase solution is oxidized to trivalent ions.

  Then, after oxidizing the total amount of Fe into trivalent ions, in this step, goethite is generated using calcium hydroxide without local pH increase, and this goethite is precipitated, Separate from aqueous phase solution. In addition, since the oxidation treatment by oxygen bubbling is effective at about pH = 4, it is desirable to carry out after the precipitation forming agent is administered, or to carry out the oxygen bubbling simultaneously with the administration of the precipitation forming agent.

1-Ga) Positive extraction step The content of this step is the same as that of the 1-F) extraction separation step of [Embodiment 1], but a diglycolamide (DGA) type extraction agent is used as the solvation extractant. Use. In particular, a solvent obtained by diluting a tridentate ligand DGA having a long alkyl chain and high lipophilicity into an ionic liquid is used as an extraction solvent. Since the ligand has three binding sites when coordinated to the metal, it is called a tridentate ligand. By performing this step, rare earth elements are extracted into the organic phase solution.
For example, the use of TODGA (O [CH ₂ CON (R) ₂ ] ₂ (R = C ₈ H ₁₇ ), N, N, N ′, N′-tetraoctyl diglycolamide) efficiently converts rare earth elements. It is also suitable from the point that it can be extracted. In addition, DGA type extractant dissolves relatively well in nonpolar solvents, and when an ionic liquid, which is a polar solvent, is used as a diluent, it does not form a third phase and is suitable for hydrolysis. is there. Here, the third phase means a heavy phase in which the metal is concentrated when the metal concentration in the organic phase increases in the extraction system.
Others include TPDGA (O [CH ₂ CON (R) ₂ ] ₂ (R = C ₃ H ₇ ), N, N, N ′, N′-tetrapropyldiglycolamide), TBDGA (O [CH ₂ CON ( _{R) 2] 2 (R =} C 4 H 9), N, N, N ', N'- tetra butyl diglycol _{amides), THDGA (O [CH 2} CON (R) 2] 2 (R = C 6 H ₁₃ ), N, N, N ′, N′-tetrahexyl diglycolamide) and the like are also suitable. _{Here, TMDGA (O [CH 2 CON} (R) 2] 2 (R = CH 3), N, N, N ', N'- tetramethyl glycol _{amide), TEDGA (O [CH 2} CON (R) ₂ ] ₂ (R = C ₂ H ₅ ), N, N, N ′, N′-tetraethyldiglycolamide), DGA into which a short-chain alkyl group is introduced exhibits water solubility and is in an aqueous phase. In this case, the rare earth species may be back-extracted into the aqueous phase by complexing with trivalent rare earth ions, which is not preferable. In addition, it is longer than an octyl group such as TDdDGA (O [CH ₂ CON (R) ₂ ] ₂ (R = C ₁₂ H ₂₅ ), N, N, N ′, N′-tetradodecyl diglycolamide). A DGA compound having an alkyl group is not preferred because of its low solubility in an ionic liquid.
When a DGA type extractant is used as the solvate extractant, the extraction mechanism of the normal extraction step is as follows. First, when [RE ³⁺ ] _aq and [Ca ²⁺ ] _aq are present alone in the aqueous phase, the extraction mechanism of the DGA type extractant proceeds as follows. Here, RE = Pr, Nd, and Dy are shown.
[RE ³⁺ ] _aq +3 [DGA] _IL +3 [P ₂₂₂₅ ] [TFSA] _IL ⇔ [RE (DGA) ₃ (TFSA) ₃ ] _IL +3 [P ₂₂₂₅ ⁺ ] _aq
[Ca ²⁺ ] _aq +2 [DGA] _IL +2 [P ₂₂₂₅ ] [TFSA] _IL ⇔ [Ca (DGA) ₂ (TFSA) ₂ ] _IL +2 [P ₂₂₂₅ ⁺ ] _aq
That is, it is a cation exchange extraction mechanism that proceeds at a molar ratio of [RE ³⁺ ] _aq : [DGA] _IL = 1: 3, [Ca ²⁺ ] _aq : [DGA] _IL = 1: 2.
On the other hand, in the solution obtained by performing the iron removal step with the precipitation forming agent Ca (OH) _{2 with} respect to the amide solution from which the actual waste is eluted, the concentration in the aqueous phase is [RE ³⁺ ] _aq << [Ca ²⁺ ] _Aq , and proceeds under the following extraction equilibrium equation under this concentration condition.
[RE ³⁺ ] _aq + [Ca ²⁺ ] _aq +3 [DGA] _IL +5 [P ₂₂₂₅ ] [TFSA] _IL ⇔ [RE (DGA) ₂ (TFSA) ₃ ] _IL + [Ca (DGA) (TFSA) ₂ ] _IL +5 [P ₂₂₂₅ ⁺ ] _aq
That is, in the rare earth mixed system having a high Ca concentration, the stoichiometric coefficient of the DGA type extractant for Ca is lower than that in the system in which Ca is present alone. The complex formation state of ²⁺ becomes weak, and the extraction rate during positive extraction decreases. Moreover, that the complex formation state of Ca ^<2+ > is weak means that the back extraction rate to the water phase side becomes high.

  On the other hand, as a result of diligent research by the present inventors, knowledge has been obtained about the points that should be improved in the above method, in particular, the problems that occur when the above method is actually used in a factory plant. The findings are as follows.

First, when the above method is continuously performed in a factory plant, it is desirable that the iron removal step is not accompanied by a local pH increase. Moreover, as a hydroxide used as a precipitation forming agent in performing the iron removal step, a hydroxide made of an electrochemically base metal rather than a rare earth element (for example, the above calcium hydroxide) is suitable. . The precipitation-forming agent (calcium hydroxide) for precipitating iron as goethite is a neutralization reaction (about 85% of the total OH ^- molar amount) in the aqueous phase solution, and a goethite precipitation-forming reaction (total OH ^- mol). About 15% of the amount), the dose must be very large. After iron ion (III) is hydroxylated with calcium hydroxide, it can be completely removed as an oxyhydroxide precipitate (goethite).

  Thereafter, when an extraction / separation step is performed, of course, the rare earth element is selectively complexed with the solvating extractant and extracted into the organic phase solution. However, some calcium is also complexed by the solvating extractant and extracted into the organic phase solution. Therefore, an organic phase solution having a relatively high content of the precipitation forming agent component (calcium) is obtained.

  As a result, in a later-described electrolytic deposition step, a relatively high proportion of calcium is mixed with the rare earth element in the organic phase solution (that is, the electrolytic bath). Then, since the solubility itself is constant, the content of the rare earth element is lowered 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 generate goethite, when the plant is continuously operated, calcium is accumulated in the electrolytic bath as the rare earth metal is recovered in the electrolytic deposition process. It will follow. Normally, calcium should not be deposited in the electrolytic deposition process, but if calcium is accumulated excessively, the deposition potential shifts to the noble side, so that calcium is co-deposited during rare earth metal deposition. Is concerned. In this case, the purity of the rare earth metal finally obtained may be reduced.

  Moreover, when performing said method continuously in a factory plant, if there is no secondary use of a precipitation formation agent, you have to procure from the outside each time. Then, when implementing this invention in a factory plant, the expense required will become a huge thing.

  Therefore, the present inventor, in addition to precipitating and separating an element (iron) that is electrochemically more noble than the rare earth element in the pre-electrolytic deposition step, is also recovered in the extraction / separation step, that is, in the present embodiment. A reverse extraction step of extracting, from the organic phase solution obtained after the normal extraction step of extracting the rare earth element as an object into the organic phase solution, reversely extracting calcium as an unnecessary material into a mineral acid that is more dilute than the amide solution. I came up with a technique to do it.

1-Gb) Back extraction step In this step, the alkali metal element or alkaline earth metal element (calcium in the present embodiment) added in the iron removal step is diluted from the organic phase solution to the amide solution. Extraction selectively into mineral acid (nitric acid in this embodiment). Here, an acid medium diluted with an amide solution is preferable because only a solvation complex involving an alkaline earth element having a weak complexation state with an extractant can be selectively extracted back to the aqueous phase side. is there. In addition, the acid medium having a higher concentration than the amide solution in the normal extraction step is not only solvated complexes involving alkaline earth elements but also solvated complexes involving rare earth elements are simultaneously back-extracted to the aqueous phase side. Therefore, it is not preferable. This is because the back extraction process proceeds by forming a stronger complex formation state on the aqueous phase side than the complex formation state with the extractant on the organic phase side, and the complex formed on the organic phase side. The formation is based on the loss of lipophilicity and progression by developing hydrophilicity. At present, when calcium is contained in the organic phase solution, it is possible to efficiently back extract calcium into nitric acid by contacting dilute nitric acid with the organic phase solution. This has been found by the investigation of the present inventors.

  By doing so, iron, boron, and trace metal species can be separated in the normal extraction step, and calcium can also be separated from the organic phase solution by the back extraction step. As a result, the rare earth element content in the organic phase solution can be significantly improved. Then, the current efficiency at the time of scale-up when the rare earth element is finally electrolytically deposited is increased, and an electrodeposit with a high purity of the rare earth metal can be obtained.

In addition, it is possible to solve the problems caused by continuously operating the factory plant. Specifically, when calcium hydroxide is used to generate goethite, calcium accumulates in the electrolytic bath as the plant plant is continuously operated in the subsequent electrolytic deposition process. End up. Normally, calcium should not be reduced, but if calcium accumulates excessively, it can be assumed that calcium co-deposits in the electrodeposit. If this happens, the purity of the rare earth element finally obtained may be reduced.
Thus, as in this step, by separating calcium from the organic phase solution at the stage before the electrolytic deposition step, it is possible to construct an electrolytic environment in which calcium does not accumulate in the first place.

The effects brought about by the present embodiment are not limited to the above contents. In the present embodiment, it is particularly preferable to have a continuous extraction process in which the normal extraction process and the reverse extraction process are alternately repeated before the electrolytic deposition process.
Hereinafter, the reason will be described by focusing on the viewpoint of “recycling” of the solvating extractant and calcium.

First, regarding calcium, as described above, in the electrolytic deposition process, if calcium is excessively accumulated, calcium causes a decrease in the purity of the rare earth element.
On the other hand, when the deironing process is continuously performed in a factory plant, if there is no secondary use of a precipitation forming agent (here, calcium hydroxide) for forming goethite, the precipitation forming agent is externally applied each time. Must be procured. Then, when implementing this invention in a factory plant, the expense required will become a huge thing.

  As a result of examining the above two problems, the present inventor has come up with a technique for solving both of the two problems by combining the two problems. That is, the inventors came up with a technique of hydroxylating calcium that was back-extracted in the back-extraction process and recycling it as a precipitate-forming agent in the de-ironing process. In other words, even in the process of recycling rare earth elements from VCM, the recycling philosophy of recovering calcium used in recycling work and reusing it to remove unnecessary materials (goethite) is exactly the same. I came up with a method to embody.

This technique is specifically described as follows.
・ Calcium hydroxide production process in which alkali (preferably non-metallic alkali) is mixed with nitric acid after back extraction process to produce calcium hydroxide ・ Calcium hydroxide and aqueous phase solution obtained in calcium hydroxide production process Is a deironation process in which goethite is generated and precipitated by mixing with, and separated from the aqueous phase solution.

  There is a great merit in using a calcium ion as an unnecessary substance existing in the organic phase solution again in the series of cycles of recovery of rare earth elements and then using it in the deironing process. First, it is not necessary to purchase calcium hydroxide separately, and the cost can be reduced. As described above, when the present invention is implemented in a factory plant, the effect is enormous.

In addition, when a prescribed amount of calcium ions cannot be obtained by only performing the above-described back extraction step once, the calcium ions or calcium hydroxide is separately stored in a storage unit.
Here, in order to increase the amount of calcium ions or calcium hydroxide, calcium may also be recovered from the aqueous phase solution after the positive extraction step. For example, calcium hydroxide may be generated by mixing an alkali (preferably a nonmetallic alkali) with the aqueous phase solution after the positive extraction step.
Moreover, in order to store calcium ions or calcium hydroxide, a continuous extraction process, which is a preferable example of this embodiment, is performed by alternately repeating the normal extraction process and the reverse extraction process.

  The “continuous extraction process” here refers to an amide solution in which rare earth species are eluted from actual waste in the normal extraction process, for example, the normal extraction process → the reverse extraction process → the normal extraction process → the reverse extraction process →. In the back extraction process, the mineral acid that is thinner than the amide solution is used as the aqueous phase, a highly polar ionic liquid is dissolved as a diluent in the DGA-type solvating extractant, and the extraction operation is repeated. is there. When the amount of metal loaded into the organic phase in the extraction process is large (when the metal complex is close to the stoichiometry), a system in which the organic solvent flow rate during continuous extraction is small can be constructed. By performing the continuous extraction step, the metal loading of the extractant is large, and the effect of increasing the proportion of rare earth species coordinated to the tridentate ligand is achieved.

  First, it becomes possible to continuously regenerate the above calcium ions or calcium hydroxide. The regenerated calcium ions or calcium hydroxide is stored in the storage unit. After a certain amount of calcium ions or calcium hydroxide has been stored, as a precipitation-forming agent during the iron removal process, calcium hydroxide in the storage part (in the case of calcium ions, this is hydroxylated) is added to the aqueous phase solution. Adopting the method is preferable in order to efficiently perform a series of cycles in a factory plant.

As another effect, of course, the rare earth element content in the organic phase solution can be improved. This is because calcium can be further separated from the organic phase solution by repeating the normal extraction step and the reverse extraction step.
In addition to the recycling of calcium ions or calcium hydroxide, the continuous extraction step has a greater effect for the solvating extractant. This will be described below.

In fact, it is not only rare earth elements that are complexed by the solvating extractant. In the stage before the back extraction process, the calcium in the organic phase solution is complexed by the solvating extractant, like the rare earth elements.
Then, after the back extraction step, the organic phase solution contains a rare earth element complexed by a solvating extractant. Further, as described above, calcium is back-extracted from the organic phase solution to nitric acid, and there is no or almost no calcium in the organic phase solution. Therefore, the solvating extractant used for complexing calcium (more precisely, the compound constituting the solvated extractant) is present alone in the organic phase solution after the back extraction step.

  Therefore, by performing the positive extraction process again, the rare earth element that could not be extracted into the organic phase solution and remained in the aqueous phase solution, and the solvation extractant that was previously used for complexing calcium and now exists alone. It can be contacted again. By doing so, the rare earth element is positively extracted into an organic phase solution, and the solvating extractant is complexed with the rare earth element. Thereafter, the back-extraction step is performed again, and the solvating extractant that separated calcium and complexed calcium is present alone. Then, the positive extraction process is performed again.

  By adopting the above-mentioned method, not only can calcium be steadily separated, but also rare earth elements can be steadily extracted into the organic phase solution. Moreover, the solvation extractant itself in the organic phase solution can also be recycled for the normal extraction step, and the function as the solvation extractant can be exhibited to the maximum extent.

  In addition, if the normal extraction step and the reverse extraction step are performed only once in this order, the solvation extractant used for complexing calcium in the subsequent electrochemical step will be present alone. . If it becomes so, if it is a solvation extractant alone, it will become a decomposition target in an electrochemical process. In this case, the solvating extractant is consumed, and the decomposition of the solvate extractant decreases the cathode current efficiency, which may inhibit the precipitation reaction of the rare earth element.

  Of course, even if the electrochemical process (electrolytic deposition process) is performed by performing the normal extraction process and the reverse extraction process only once in this order, the effects of the present embodiment and the above-described embodiments are exhibited. However, it is possible to dramatically improve the value of the present embodiment by solving the above-mentioned matters to be considered.

  And in order to solve said matter which should be considered, when performing a continuous extraction process, ending with a normal extraction process is mentioned. That is, the continuous extraction process is configured to start at the normal extraction process and end at the normal extraction process, such as normal extraction process → back extraction process → normal extraction process → back extraction process → normal extraction process. By doing so, since the positive extraction step is performed immediately before the electrochemical step, the solvation extractant is complexed with the rare earth element, and there is relatively little solvation extractant alone. It has become. As a result, “consumption of solvation extractant” and “decrease in cathode current efficiency” as described above hardly occur.

  As described above, after the 1-Gc) continuous extraction step is performed, the 1-H) electrochemical step is performed. This content is as described in the above embodiment.

  In this embodiment, the mineral acid used in the back extraction step is nitric acid because the hydroxide of the alkali metal element or alkaline earth metal element added in the separation step is calcium hydroxide. The acid may contain a substance other than nitric acid that does not inhibit the back extraction process. Further, a hydroxide of an alkali metal element or an alkaline earth metal element may be used as another compound, or a combination of calcium hydroxide and another compound may be used. However, in that case, a mineral acid capable of performing the back extraction step is selected.

Next, an Example is shown and this invention is demonstrated concretely. 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.

  First, roughly, in <Example 1> to <Example 5>, the iron removal step is not performed as described in [Embodiment 1], while <Example 6> to <Example 7>. In No. 2, the iron removal step is performed as described in [Embodiment 2].

Specifically, in <Example 1> and <Example 2>, the results of the “rare earth electrolysis test from actual waste VCM” which is one of the specific examples of the present invention will be described.
And in <Example 1>, it describes about the result of collect | recovering Nd, and in <Example 2>, it describes about the result of collect | recovered Nd and Dy.

In <Example 3>, when the volume ratio of the aqueous phase solution to the organic phase solution was 1: 1, the rare earth element concentration was changed when the concentration of the solvating extractant present in the organic phase solution was changed. It was investigated how the extraction ratio to the organic phase solution changed.
In <Example 4>, conversely, when the concentration of the solvating extractant present in the organic phase solution is constant, the rare earth element is changed when the volume ratio of the aqueous phase solution to the organic phase solution is changed. It was investigated how the extraction ratio of to the organic phase solution changed.

In <Example 5> and <Comparative Example 1>, even if the anion species constituting the acid in the aqueous phase solution and the anion species constituting the ionic liquid in the organic phase solution are the same species, the extraction rate In view of the above, is the hydrophobic anion species TFSA ⁻ (Example 5) derived from an organic acid (amide solution) more effective, or NO ₃ ⁻ (Comparative Example 1) where the same anion species is derived from a mineral acid? I examined whether it was more effective.
Furthermore, TFSA is configurable hydrophobic anionic species ionic liquid ^- was investigated whether whether it is possible to recover the rare earth element in whether contained in the aqueous phase solution and the organic phase solution is changed .

And in <Example 6> and <Comparative Example 2>, in order to show what organic phase solution is qualified or unqualified, using the deironing step described in [Embodiment 2] above, It describes about the result of having collect | recovered Nd and Dy after using the method of carrying out precipitation separation of Fe beforehand before an extraction separation process.
In <Example 6>, [P ₂₂₂₅ ] [TFSA] (triethyl-pentyl-phosphonium bis (trifluoromethyl-sulfonyl) amide) was used as the organic phase solution.
On the other hand, in <Comparative Example 2>, [EMI] [TFSA] (1-ethyl-3-methyl-imidazolium bis (trifluoromethyl-sulfonyl) amide amide) was used as the organic phase solution.

In <Example 7>, in order to verify the effectiveness when the hydrophobic anion species constituting the acid in the aqueous phase solution and the anion species constituting the ionic liquid in the organic phase solution are the same species, the removal is performed. When the concentration of the same kind of anion species was changed in the aqueous phase solution after performing the iron process, it was examined how the extraction ratio of the rare earth element to the organic phase solution changed. As the “extraction ratio” mentioned here, “distribution ratio (D)” of a compound containing a rare earth element generated by solvation to an organic phase solvent was used as one of the indexes.
Hereinafter, description will be made in order from <Example 1>.

<Example 1> (Nd recovery from actual waste VCM)
In this example, according to the flowchart shown in FIG. 1, a rare earth element recovery step was performed using a used VCM for 3.5 inch HDD. In addition, about the codes | symbols, such as 1-A) and 1-B), the code | symbol based on [Embodiment 1] is used.

1-A) Dismantling / sorting step First, after disassembling the actual waste and separating the VCM, only the member as the rare earth magnet was recovered from the VCM.

1-B) Thermal Demagnetization Step The thermal demagnetization step was performed as follows. That is, a member as a rare earth magnet was placed on a firing setter, held in an alumina crucible, and then placed in an electric furnace. As a temperature program for the thermal demagnetization process, the temperature increasing / decreasing rate up to the Curie temperature (310 ° C.) was set to 100 ° C./h in an air atmosphere. By this thermal demagnetization process, the initial magnetic flux density: 410 to 445 mT is reduced to the residual magnetic flux density: 0.01 mT (demagnetization factor: 99.9% or more) while suppressing the formation of the oxide film on the surface of the member as the rare earth magnet. Lowered. This facilitated the subsequent handling of the member as a rare earth magnet.

1-C) Plating peeling process In the plating peeling process, the Ni plating layer on the surface of the member as a rare earth magnet was eluted using an alkaline plating peeling agent. After preparing an aqueous solution containing an alkaline plating release agent to pH 12 or higher, a member (demagnetized) as a rare earth magnet was put into the aqueous solution. And it stirred at 50-70 degreeC and 100 rpm on the hot stirrer, and the plating layer was eluted. The plating layer of the member as a rare earth magnet formed a three-layer structure in which a Ni layer (surface layer), a Cu layer (intermediate layer), and a Ni layer (deepest layer) were laminated in this order. Therefore, after the Ni of the surface layer was eluted with the plating release agent, the Cu layer was removed by polishing treatment. Thereafter, Ni in the deepest layer was eluted using a plating remover as described above.

1-D) Oxidation roasting step After the plating release agent was sufficiently diluted and removed with distilled water, the member as the rare earth magnet after the plating layer was eluted was dried in a dryer. The member as a rare earth magnet was pulverized using an automatic mortar. Thereafter, the pulverized member as a rare earth magnet was spread on an alumina container, and an oxidative roasting process was performed under conditions of 860 ° C. and 2 hours in an air atmosphere. And again, using an automatic mortar, the member as a rare earth magnet was pulverized until the particle diameter became 30 μm or less.

1-E) Elution Step In the elution step, a solution containing an acid composed of a hydrophobic anionic species capable of constituting an ionic liquid was used as the aqueous phase solution. As this solution, HTFSA (2.0 M) was used. 25 g of a member (resource) as a finely divided rare earth magnet was put into 250 ml of HTFSA. Then, HTFSA and resources were reacted on a hot stirrer under the conditions of 100 ° C., 700 rpm, and 12 hours. Thereafter, centrifugation and filtration were performed to remove unreacted resources.

表１に示す通り、水相溶液としてＨＴＦＳＡを用いた場合、希土類元素であるＰｒ及びＮｄの溶出量は高い一方、Ｆｅの溶出量は低く抑えられていた。その結果、上記の実施形態で述べたように、本発明の効果を奏する上で、ＨＴＦＳＡは好適であることが確認された。 Here, in order to confirm which element is likely to elute with respect to HTFSA which is an aqueous phase solution, the obtained aqueous phase solution was analyzed for ionic species by ICP-AES. The results are shown in Table 1. In addition to the case where the resource is eluted in the aqueous phase solution, as a comparison target, the case where the resource is eluted in nitric acid (2.0M) and the case where the resource is eluted in hydrochloric acid (2.0M) Also described.

As shown in Table 1, when HTFSA was used as the aqueous phase solution, the elution amount of the rare earth elements Pr and Nd was high, while the elution amount of Fe was kept low. As a result, as described in the above embodiment, it was confirmed that HTFSA is suitable for achieving the effects of the present invention.

1-F) Extraction / separation step In the extraction / separation step, 3.0 ml of [P ₂₂₂₅ ] [TFSA] (1.41 M), which is an ionic liquid, was added as an organic phase solution before extraction to the aqueous phase solution. In this example, HTFSA is positioned as an aqueous phase, and [P ₂₂₂₅ ] [TFSA] is positioned as an organic phase. In the extraction / separation step, 1.84 M TBP (tri-n-butyl phosphate) was added in advance to the organic phase solution before extraction as an additive (solvation extractant) for extraction. The volume ratio of the aqueous phase solution to the organic phase solution was 1: 1.

  Here, in order to confirm whether or not the rare earth element is appropriately extracted in this step and whether or not iron is not extracted, the pH of the organic phase solution after the extraction is compared with the organic phase solution after the extraction. The extraction rate of each element according to the above was investigated. The result is shown in FIG.

  From FIG. 2, the extraction rate of 90% or more was maintained for the rare earth elements, and the extraction rate of about 60% for Fe was able to be maintained. Furthermore, when the pH is 0.5 or less, the extraction rate of 60% or more can be maintained for rare earth elements, and the extraction rate for Fe has been successfully reduced to almost 0%.

  Based on the above results, under the condition of pH = 0.02, the organic phase was fixed to the above conditions, and then continuous extraction was performed by replacing only the aqueous phase side with a new medium. As a result of repeating this continuous extraction process 10 times, the concentration of rare earth elements in the organic phase solution after extraction was Pr = 4.68 mM, Nd = 22.24 mM, Dy = 1.06 mM. The metal concentration of the organic phase solution after extraction was calculated by collecting the aqueous phase at each stage during continuous extraction and performing ICP-AES analysis. Moreover, about Fe and B, it was not detected from the organic phase solution after extraction at all the extraction steps.

  Thereafter, as a preparation for the subsequent 1-G) electrochemical step, the organic phase solution after extraction was evaporated in a draft for 12 h. Thereafter, a vacuum drying process was performed for 48 hours or more for further water removal in the electrolytic bath.

1-G) Electrochemical Step FIG. 3 shows an electrolytic test apparatus used in the electrochemical step in this example. The electrolysis test apparatus in this example is an apparatus using a three-electrode electrolysis cell. Although an electrolysis test apparatus itself may use a well-known thing, an outline | summary is demonstrated below.

The electrolysis test apparatus 1 in the present embodiment has an anode part 2, a glass member 3 containing the anode part 2, a cathode part 4, a reference electrode part 5, and an electrolytic cell 6 in which these can be accommodated. Moreover, although not shown in figure, the three-electrode system electrolysis control apparatus which has the integral electric energy function is also provided.
The electrolysis control device and the anode part 2 and the cathode part 4 are electrically connected. And it can be made to apply to the setting electric potential on the basis of a reference electrode with an electrolysis control apparatus.
In addition, a heat-resistant wool 7 that suppresses heat radiation from the electrolytic cell 6, a mantle heater 8 based on PID temperature control on the outside thereof, and a hot stirrer 9 are provided below these. A stirring bar 10 is provided inside the electrolytic cell 6. The upper part of the electrolysis cell 6 is sealed with a silicon plug 11. A glass member 3 (anode portion 2), a cathode portion 4, a reference electrode portion 5 and a thermocouple 12 for controlling the temperature of the electrolytic bath are provided so as to penetrate the silicon stopper 11.
In this embodiment, a demagnetized waste magnet member is used as the anode portion 2. And the said waste magnet member is being fixed using the anode lead wire (not shown). And the anode part 2 is arrange | positioned in the hollow glass member 3 which consists of soda-lime glass. In addition, the glass filter 13 (Vycor glass filter) is installed in the front-end | tip (top and bottom side of the glass member 3).

An extracted organic phase solution (electrolytic bath) 14 serving as an electrolytic bath is introduced into the electrolytic cell 6. At the same time, an organic phase solution (anode side) 15 after extraction is put into the glass member 3, and an anode which is a demagnetized waste magnet member is added to the organic phase solution (anode side) 15 after extraction. Part 2 is immersed. Finally, the glass member 3 containing the extracted organic phase solution (anode side) 15 is immersed in the extracted organic phase solution (electrolytic bath) 14.
The post-extraction organic phase solution (electrolytic bath) 14 and the post-extraction organic phase solution (anode side) 15 are both separated from the post-extraction organic phase solution after the 1-F) extraction separation step.

  The glass filter 13 is made of Vycor glass, and the extracted organic phase solution (anode side) 15 is diffused into the extracted organic phase solution (electrolytic bath) 14 which is put into the electrolytic cell 6 and becomes an electrolytic bath. First, the demagnetized waste magnet member and the insoluble material that are eluted as the anode part 2 are held in the vicinity of the anode part 2. Thus, the electrolytic test apparatus 1 in this example was designed. The glass filter 13 has a structure in which a current flows by increasing the applied voltage.

1-Ga) Anodic dissolution step and 1-Gb) First electrolytic deposition step In this example, 1-Ga) anodic dissolution step and 1 -Gb) The 1st electrolytic deposition process was performed simultaneously.
In the first electrolytic deposition step in this example, the anode part 2 was an Nd—Fe—B rod, the cathode part 4 was a Cu substrate, and the reference electrode part 5 was a Pt wire. In addition, the cathode part 4 was made into the structure which enlarges an electrode area by making Cu board | substrate substantially cylindrical shape. Then, Nd was deposited under the conditions of electrolytic bath temperature: 100 ° C., electrolytic atmosphere: Ar, applied voltage: −3.2 V, and total electric quantity: 96.2 C. As a result, when it was assumed that the anode current efficiency was 90.3%, the cathode deposit was 35.2 mg, and the electrolytic deposit was composed only of Nd, the cathode current efficiency was 73.4%, and the cathode recovery rate. Was 36.7%. Extremely high anode current efficiency was obtained. The anode current efficiency was calculated from the ratio of the actual weight change amount to the theoretical weight decrease amount of the anode (Nd electrode) calculated from the total amount of electricity (the same applies hereinafter).
That is, if the total amount of electricity is high, if the electrolysis time is constant, the value of the current flowing between the anode and the cathode increases, and the amount of Nd deposited on the cathode increases. Further, if the anode current efficiency is high, it means that electrolytic deposition is performed as close as theoretically possible, and there is no problem in the electrochemical reaction on the anode side.

Then, XPS analysis (X-ray Photoelectron Spectroscopy: XPS) was performed on the obtained deposit. FIG. 5 is a graph showing the results of XPS analysis performed on the electrodeposits obtained in Example 1. As a result, in the Nd3d _5/2 spectrum, a peak was prominent at 981.5 eV at a depth of 0.2 μm from the outermost surface layer, which was an intermediate state between the oxide phase and the metal phase. On the other hand, at a depth of 0.9 μm from the outermost surface layer, a peak was prominent at 980.7 eV, confirming the formation of a metal phase. Moreover, the result of having conducted the depth direction analysis of the deposit is shown in FIG. The carbon concentration and oxygen concentration decreased with the depth direction of the electrodeposit, and it was confirmed that C <0.1% and O <1.0% at a depth of 0.9 μm. That is, relatively high purity Nd was formed as a precipitate inside a slight depth from the outermost surface layer.
In the following embodiments, when displaying in the depth direction, a minus value such as −0.2 μm may be given.

<Example 2> (Recovery of Nd and Dy from actual waste VCM)
1-A) Disassembly / sorting step 1-E) The elution step was the same as in <Example 1>. Further, items not specifically mentioned below were the same as those in <Example 1>.

  1-F) In the extraction / separation step, the continuous extraction step of sequentially changing the aqueous phase side after setting the pH to 0.02 was repeated seven times. As a result, the concentration of rare earth elements in the organic phase solution after extraction was Pr = 5.6 mM, Nd = 18.69 mM, Dy = 0.84 mM. Fe and B were not detected from the organic phase solution after extraction.

  In 1-Ga) anodic dissolution step and 1-Gb) first electrolytic deposition step, electrolytic bath temperature: 120 ° C., electrolytic atmosphere: Ar, applied voltage: −3.25 V, total electric quantity : Nd was deposited under the condition of 116.2C. As a result, when it was assumed that the anode current efficiency was 92.1%, the cathode deposit was 41.6 mg, and the electrolytic deposit was composed only of Nd, the cathode current efficiency was 71.8%, and the cathode recovery rate. Was 41.6%.

As a result of XPS analysis of the obtained electrodeposit, the outermost surface layer was in an intermediate state between the oxide phase and the metal phase in the Nd3d _5/2 spectrum. On the other hand, formation of a metal phase could be confirmed inside a slight depth from the outermost surface layer. Moreover, as a result of analyzing the depth direction of the deposit, it was confirmed that the carbon concentration and the oxygen concentration were decreased. That is, relatively high purity Nd was formed as a precipitate inside a slight depth from the outermost surface layer.

1-Gc) Second electrolytic deposition step In the second electrolytic deposition step, the anode part 2 is a Dy rod and the cathode part 4 is a Cu substrate, the electrolytic bath temperature is 120 ° C, the electrolytic atmosphere is Ar, and the applied voltage is: Dy was deposited under the conditions of -3.75 V and total electricity: 35.4 C. In addition, as the electrolytic bath, 1-Gb) the low-temperature melt (electrolytic bath) 14 after being used in the first electrolytic deposition step was used.
As a result, the anode current efficiency was 91.5%, and the cathode deposit was 13.1 mg.

  The obtained electrodeposit was analyzed by XPS. FIG. 7 is a graph showing the results of analyzing the depth direction by XPS of the electrodeposit obtained in the second electrolytic deposition step of Example 2. As a result, it was revealed that the electrodeposits co-deposited with Nd in a Dy-rich state. Moreover, it was confirmed that the carbon concentration and the oxygen concentration decreased with the depth direction, and the carbon concentration and the oxygen concentration were 0.5% or less at a depth of 1.05 μm from the outermost surface layer. That is, like Nd, Dy having a relatively high purity was formed as a precipitate inside a slight depth from the outermost surface layer.

<Example 3> (Change in rare earth extraction rate depending on the concentration of the solvating extractant)
In this example, when the volume ratio of the aqueous phase solution to the organic phase solution is 1: 1, the concentration of the solvating extractant present in the organic phase solution is changed to the rare earth element organic phase solution. We investigated how the degree of extraction changes. Note that the contents (devices and methods used) not described in the following examples are the same as in the above <Example 1>.

1-E) Elution step 2.0 g of oxidized and roasted VCM fine powder was dissolved in 200 ml of 2.0M-HTFSA solution at 70 ° C. and 500 rpm for 12 hours. After removing unreacted fine powder by filtration, the elution concentration of each metal in HTFSA was confirmed by ICP-AES analysis. As a result, Fe: 7.63 mM, Pr: 3.04 mM, Nd: 11.69 mM, Dy: 0.54 mM.

表２を見ると、ＴＢＰ濃度の増加とともに希土類種の抽出率は増加傾向にあることがわかる。また、ＴＢＰ濃度が２．４５Ｍ以上では、Ｆｅが抽出されていた。ＢはＴＢＰの全濃度範囲において、抽出されていなかった。その結果、現在確認できている段階では、抽出分離工程においては、Ａ／Ｏを１．０とした場合、前記溶媒和抽出剤の濃度が１．２３Ｍ以上２．１５Ｍ以下である場合、ＦｅやＢを全く含むことなく、希土類種を有機相溶液へと更に有効に抽出することが可能となることがわかった。 1-F) Extraction Separation Step An extraction test (2000 rpm, 5 min) was performed by using this solution as an aqueous phase and changing the solvation extractant TBP concentration stepwise from 1.23 M to 3.07 M. At that time, the volume of the organic phase (ionic liquid phase + solvating extractant) was kept constant at 6.0 ml. The ratio of the volume of the aqueous phase (A) to the volume of the organic phase (O) was unified to A / O = 1.0, and the extraction test was conducted. The solvating extractant concentration and extraction rate were as follows.

Table 2 shows that the extraction rate of rare earth species tends to increase with increasing TBP concentration. Further, Fe was extracted at a TBP concentration of 2.45M or more. B was not extracted in the whole concentration range of TBP. As a result, at the currently confirmed stage, in the extraction / separation step, when A / O is 1.0, the concentration of the solvating extractant is 1.23 M or more and 2.15 M or less, Fe or It has been found that the rare earth species can be extracted more effectively into the organic phase solution without containing B at all.

  FIG. 8 shows the relationship between the TBP concentration and the distribution ratio in each rare earth element. From FIG. 8, the slope of the linear relationship of each rare earth species is Pr: 2.48, Nd: 2.11, Dy: 2.74, and it is confirmed that the process proceeds with an almost constant extraction mechanism regardless of the rare earth species. did.

表３に示すように、全てのＡ／Ｏ比において、Ｆｅ，Ｂは有機相側に抽出されなかった。０．５≦Ａ／Ｏ≦１．０の条件下で脱鉄処理と効率的な希土類抽出を両立できることが判明した。特に、現在確認されている範囲では、溶媒和抽出剤の濃度を１．８４Ｍとした場合、Ａ／Ｏが０．５以上１．０以下であれば、ＦｅやＢを全く含むことなく、希土類種を有機相溶液へと更に有効に抽出することが可能となることがわかった。 <Example 4> (Change of rare earth extraction rate according to A / O ratio)
In Example 3, 1-E) The solution used in the elution step was used as an aqueous phase, the solvation extractant TBP concentration was unified to 1.84 M, and the ratio of the volume of the aqueous phase to the volume of the organic phase: A / O = Extraction test (2000 rpm, 5 min) was performed by changing from 0.5 to 5.0. The extraction test results for each A / O are shown in Table 3.

As shown in Table 3, Fe and B were not extracted to the organic phase side at all A / O ratios. It was found that both iron removal treatment and efficient rare earth extraction can be achieved under the condition of 0.5 ≦ A / O ≦ 1.0. In particular, within the currently confirmed range, when the concentration of the solvating extractant is 1.84M, if A / O is 0.5 or more and 1.0 or less, the rare earth is not contained at all without including Fe or B. It has been found that seeds can be extracted more effectively into organic phase solutions.

<Example 5> and <Comparative example 1> (Comparison between the case where the common anion species is [NO ₃ ⁻ ] and [TFSA ⁻ ])
In this example, even if the anion species constituting the acid in the aqueous phase solution and the anion species constituting the ionic liquid in the organic phase solution are the same species, the organic acid (amide solution) ) Derived hydrophobic anion species [TFSA ⁻ ] (Example 5) or [NO ₃ ⁻ ] (Comparative Example 1) from which the anion species of the same type is derived from mineral acid is more effective. I investigated whether or not.
Furthermore, TFSA is configurable hydrophobic anionic species ionic liquid ^- was investigated whether whether it is possible to recover the rare earth element in whether contained in the aqueous phase solution and the organic phase solution is changed .

<Example 5> (Investigation of the effect of hydrophobic and semi-hydrophobic anion species on rare earth extraction rate and electrolysis)
1-E) Elution step (common anion [TFSA ⁻ ])
On the other hand, 2.0 g of finely pulverized oxidized roasted VCM was eluted for 12 h at 70 ° C. and 500 rpm with respect to 200 ml of 2.0 M-HTFSA solution.

1-F) Extraction separation step (common anion [TFSA ⁻ ])
Using this solution as an aqueous phase, [P ₄₄₄₁₆ ] [TFSA] (volume 3.0 ml), [P ₆₆₆₁₄ ] [TFSA] (volume 3.0 ml) hydrophobic ionic liquids having [TFSA] as a common anion are mixed with TBP ( The extraction test was conducted using the sample to which the concentration of 1.84M and volume of 3.0 ml) was added as the organic phase.
[P ₄₄₄₁₆ ] is officially tributylhexadecylphosphonium.
[P ₆₆₆₁₄ ] has the official name trihexyl tetradecylphosphonium.

<Comparative Example 1>
1-E) Elution step (common anion [NO ₃ ⁻ ])
From 200 ml of 2.0M-HNO ₃ solution, 2.0 g of finely pulverized oxidized roasted VCM was eluted at 70 ° C. and 500 rpm for 12 hours.

1-F) Extraction and separation step (common anion [NO ₃ ⁻ ])
After removal of the fines product of unreacted filtration, the solution as an aqueous phase, [NO _3] and a common anion _{[P 44416] [NO 3]} ( volume of about _{2.0ml), [P 66614] [} NO ₃ ] (Volume: about 3.0 ml) A semi-hydrophobic ionic liquid added with TBP (concentration: 1.84 M, volume: about 2.0 ml or volume: about 3.0 ml) was subjected to an extraction test using the organic phase. Here, semi-hydrophobic means that complete hydrophobicity is not expressed, and that the synthesized ionic liquid component is partially soluble in the aqueous phase.

希土類種の抽出率は、[ＴＦＳＡ]系抽出の方が[ＮＯ_３]系抽出よりも高いことが判明した。なお、粘性の低い[Ｐ_{４４４１６}]をカチオン種とするイオン液体の方が、粘性が高い[Ｐ_{６６６１４}]をカチオン種とするイオン液体よりも、希土類抽出率が高いことも判明した。 In both extraction tests, it was performed under the condition of A / O = 1.0. A / O refers to (volume of aqueous phase solution) / (volume of organic phase solution). The extraction test results are shown below.

The extraction rate of rare earth species was found to be higher in [TFSA] -based extraction than [NO ₃ ] -based extraction. Incidentally, who ionic liquid with low viscosity [P _44416] and the cationic species, than the ionic liquid of high viscosity [P _66614] and the cationic species has also been found that high rare earth extraction rate.

  Next, after evaporating these four kinds of ionic liquids at 100 ° C., vacuum drying was performed at 90 ° C. for 48 hours or more. After vacuum drying, an electrolytic test was performed using an Nd—Fe—B rod for the anode portion 2, a Cu substrate for the cathode portion 4, and a Pt wire for the reference electrode portion 5. The electrolysis conditions were set to electrolytic bath temperature: 100 ° C. and applied voltage: −3.25V.

As a result, no _deposit was obtained from the rare earth extracted ionic liquid using [P ₄₄₄₁₆ ] [NO ₃ ], [P ₆₆₆₁₄ ] [NO ₃ ] as an electrolytic bath. One of the reasons is that the rare earth element concentration in the electrolytic bath is low and the decrease in overvoltage with respect to the rare earth element deposition potential does not work remarkably, or that the potential window of the ionic liquid having [NO ₃ ] as an anion is small. Conceivable. As a result, it became clear that [P ₄₄₄₁₆ ] [NO ₃ ], [P ₆₆₆₁₄ ] [NO ₃ ] cannot be used as an electrolytic bath. At least in this example, the ionic liquid [P ₄₄₄₁₆ ] [NO ₃ ] and [P ₆₆₆₁₄ ] [NO ₃ ], which has [NO ₃ ] as an anion, exhibits the functionality of the hydrophobic ionic liquid even in the extraction separation process. It means that it is difficult to be used and is not suitable as an organic phase solution before extraction.

On the other hand, a black electrodeposit was obtained from the organic phase solution after extraction using [P ₄₄₄₁₆ ] [TFSA], [P ₆₆₆₁₄ ] [TFSA] as an electrolytic bath. As a result of confirming the electrodeposit by EDX analysis, it was confirmed to be Nd metal. Therefore, at least in this embodiment, as the organic phase solution that can be used as an electrolytic bath, it is effective to use an ionic liquid having phosphonium as a cation species among hydrophobic ionic liquids having TFSA as an anion. It became clear.

<Example 6> (Recovery of Nd and Dy using a method of separating Fe by precipitation)
In this example, the test was performed according to the flowchart shown in FIG. The 1-A) dismantling / sorting process to 1-D) the oxidation roasting process were the same as in <Example 1>. Further, items not specifically mentioned below were the same as those in <Example 1>. In addition, about the codes | symbols, such as 1-A) and 1-B), the code | symbol based on [Embodiment 2] is used.

  1-E) In the elution step, HTFSA (1.0 M) was used as the aqueous phase solution. 10 g of a member (resource) as a finely divided rare earth magnet was put into 250 ml of HTFSA. Then, HTFSA and resources were reacted on a hot stirrer under the conditions of 100 ° C., 700 rpm, and 24 hours. Thereafter, centrifugation and filtration were performed to remove unreacted resources.

Thereafter, in this example, 1-F) a deironing step was newly performed.
As described in [Embodiment 2], concentrated nitric acid is added to the aqueous phase solution to oxidize Fe to trivalent ions in order to avoid coprecipitation of divalent Fe ions and rare earth elements. It was.

Thereafter, a precipitation titration step was performed. KOH was used as a precipitate-forming agent into the aqueous phase solution. Then, pH 4.6 was set as the end point, and precipitation titration of [Fe (OH) _x ] ^3-x was performed. As a separation method after the formation of the precipitate, a centrifugal separation method with little loss of the solution was adopted, and the goethite which is the precipitate and the aqueous phase solution were separated.
In addition, as a result of analyzing the obtained solution by ICP-AES, it confirmed that Fe was 0 ppm and the wet separation rate was 100%.

なお、[ＤＥＭＥ]の正式名称はＮ，Ｎ−ジエチル−Ｎ−メチル−（Ｎ−２−メトキシエチル）アンモニウムである。
また、[ＭＥＭＰ]の正式名称はＮ−（２−メトキシエチル）−Ｎ−メチル−ピロリジニウムである。 1-G) In the extraction / separation step, three types of organic phases are used as diluents: [P ₂₂₂₅ ] [TFSA] (concentration 1.41M), [DEME] [TFSA] (concentration 1.46M), [MEMP]. After collecting 10 ml of [TFSA] (concentration 1.69M), 10 ml each of TBP (concentration 1.84M) was added. Thereafter, 20 ml of an aqueous phase was added to each organic phase. And it stirred for 1 h at pH 4.5, 25 degreeC, and 600 rpm. And this process was repeated 7 times and the continuous extraction was performed. The results are shown in Table 5. Table 5 shows the rare earth element distribution ratio for each number of extractions = the rare earth element concentration in the organic phase / the rare earth element concentration in the aqueous phase.

The official name of [DEME] is N, N-diethyl-N-methyl- (N-2-methoxyethyl) ammonium.
The formal name of [MEMMP] is N- (2-methoxyethyl) -N-methyl-pyrrolidinium.

  As can be seen from Table 5, in the first extraction, a high partition ratio of 46 to 183 was obtained, and rare earth ions could be extracted efficiently in the first extraction.

Regarding the rare earth element concentration in the organic phase solution obtained after continuous extraction, Pr = 54 mM, Nd = 138 mM, and Dy = 34 mM in the case of [P ₂₂₂₅ ] [TFSA]. In the case of [DEME] [TFSA], Pr = 52 mM, Nd = 134 mM, and Dy = 33 mM. In the case of [MEMP] [TFSA], Pr = 52 mM, Nd = 134 mM, and Dy = 33 mM. Regardless of which diluent was used, the rare earth element concentration was relatively high. Fe and B were not detected from the organic phase solution after extraction.

In the 1-Ha) anodic dissolution step and 1-Hb) first electrolytic deposition step, [P ₂₂₂₅ ] [TFSA] is selected as the electrolytic bath, the electrolytic bath temperature is 100 ° C., and the electrolytic atmosphere : Ar, applied voltage: -3.2V, total electric quantity: 526C, Nd was deposited. As a result, the anode current efficiency was 93.2%, the cathode deposit was 186.5 mg, and the cathode current efficiency was 71.2% when the electrolytic deposit was assumed to be composed only of Nd. A relatively high anode current efficiency was obtained.

As a result of XPS analysis of the obtained electrodeposit, the outermost surface layer was in an intermediate state between the oxide phase and the metal phase in the Nd3d _5/2 spectrum. On the other hand, formation of a metal phase could be confirmed inside a slight depth from the outermost surface layer. Moreover, as a result of analyzing the depth direction of the deposit, it was confirmed that the carbon concentration and the oxygen concentration were decreased. That is, relatively high purity Nd was formed as a precipitate inside a slight depth from the outermost surface layer.

1-Hc) Second electrolytic deposition step In the second electrolytic deposition step, the anode part 2 is a Dy rod and the cathode part 4 is a Cu substrate, the electrolytic bath temperature is 100 ° C., the electrolytic atmosphere is Ar, and the applied voltage is: Dy was deposited under the conditions of -3.7V, total electricity: 200C. In addition, as the electrolytic bath, 1-Gb) the low-temperature melt (electrolytic bath) 14 after being used in the first electrolytic deposition step was used.
As a result, the anode current efficiency was 91.8%, and the cathode precipitate was 70.3 mg.

表６に示すように、第一電解析出工程においてはＮｄを良好に回収できており、第二電解析出工程においてはＤｙを良好に回収できでいた。 Then, the cathode deposit in each electrolytic deposition step was subjected to EDX analysis (Energy Dispersive X-ray spectroscopy: EDX). The results are shown in Table 6.

As shown in Table 6, Nd was successfully recovered in the first electrolytic deposition step, and Dy was successfully recovered in the second electrolytic deposition step.

<Comparative example 2>
In Comparative Example 2, [EMI] [TFSA] (concentration 1.95 M, volume 10 ml) was used instead of [P ₂₂₂₅ ] [TFSA] used as the organic phase solution before extraction in <Example 6>. Otherwise, it was the same as <Example 6>.

  Then, with respect to the organic phase solution after extraction obtained in Comparative Example 2, whether or not the organic phase solution after extraction can be used as an electrolytic bath, that is, the rare earth element is reduced when the organic phase solution after extraction is used as an electrolytic bath. Investigate whether it can be done. Specifically, electrochemical measurement was performed using the organic phase solution after extraction as an electrolytic bath at 100 ° C. The result is shown in FIG. FIG. 9 is a graph showing whether or not an oxidation-reduction reaction occurs in the organic phase solution after extraction in Comparative Example 2.

  As a result, in [EMI] [TFSA], the potential window on the reduction side was narrow, and a peak associated with the decomposition of the cation was generated at around -2.5V. [EMI] [TFSA] extracted some rare earth ions, but the rare earth precipitates were not obtained in the electrolytic test. As a result, it was revealed that [EMI] [TFSA] cannot be used as an electrolytic bath. This is mainly due to the narrow potential window on the cation side, and [EMI] [TFSA] can be applied to the process of extracting and separating rare earth elements alone, but the electrolysis process is considered, and rare earth species are considered. [EMI] [TFSA] was found to be ineligible when recovering in the metal form. At least under the conditions of Comparative Example 2 (Example 6), [EMI] [TFSA] means that the performance of the cation is ineligible. That is, at least under the conditions of Comparative Example 2 (Example 6), [EMI] [TFSA] is not included in the “organic phase solution that can be used as an electrolytic bath used in electrolytic deposition”.

Also in <Example 6>, electrochemical measurement was performed. The result is also shown in FIG. As a result, when [P ₂₂₂₅ ] [TFSA] was used as an electrolytic bath, there was a clear difference between before and after extraction of rare earth elements. Specifically, in the case of the organic phase solution after extraction, a reduction peak of Nd was observed before the cation decomposition on the reduction side. As a result, it was confirmed that [P ₂₂₂₅ ] [TFSA] was qualified as “an organic phase solution that can be used as an electrolytic bath used for electrolytic deposition”. At this stage, the electrochemical behavior of the solvating extractant is not clear.

<Example 7> (Extraction test using a common anion using a method of separating Fe by precipitation)
In this example, in order to verify the effectiveness when the hydrophobic anion species constituting the acid in the aqueous phase solution and the anion species constituting the ionic liquid in the organic phase solution are the same species, We investigated how the degree of extraction of rare earth elements into the organic phase solution changes when the concentration of the same kind of anionic species is changed.
Moreover, even when the aqueous phase solution is a mineral acid such as HCl, if the hydrophobic anion species capable of forming an ionic liquid is added to the aqueous phase solution, the aqueous phase solution can be efficiently used. It has been proved that rare earth elements can be recovered.

1-E) Elution Step First, 5.0 g of oxidized magnetic powder was eluted in 500 ml of 1.0 M HCl solution at 70 ° C. and 500 rpm for 12 hours.

1-F) Deironing Step After filtering the unreacted oxide magnetic powder, 1.5 ml of concentrated nitric acid was added to the aqueous phase solution (HCl solution) and reacted at 500 rpm for 12 hours. In this way, Fe ²⁺ was completely converted to Fe ³⁺ in the aqueous phase solution. Thereafter, goethite was selectively precipitated and separated under the condition of pH = 3.8 using 1.0M NaOH as a precipitation forming agent. After centrifuging the solution (10000 rpm, 5 min), the supernatant (aqueous phase solution) was separated.

1-G) Extraction and separation step Thereafter, in order to examine how the degree of extraction of rare earth elements into the organic phase solution changes when the concentration of the same kind of anion species is changed in the aqueous phase solution, the following operation is performed. Went. That is, Li [TFSA] or Li [FSA] is added to 10 ml of aqueous phase solution under the conditions of concentrations of 0.05M, 0.1M, 0.2M, 0.5M, 1.0M, and 2.0M. did. On top of that, the concentration of the solvating extractant TBP was fixed at 1.23 M, and [P ₂₂₂₅ ] [TFSA] or [P ₂₂₂₅ ] [FSA] was used as a diluent under the condition of an organic phase volume of 10 ml. An extraction test (2000 rpm, 5 min) was performed.
In this example, the process was stopped by the 1-G) extraction and separation step.

When the common anion species is [TFSA ⁻ ] or [FSA ⁻ ], the metal concentration in the organic phase solution after the extraction separation process is quantitatively analyzed by ICP-AES, and the distribution ratio of the rare earth element to the concentration of the anion species (D) was examined. The result is shown in FIG. (A) shows the result when the rare earth element is Pr, (b) shows the result when the rare earth element is Nd, and (c) shows the result when the rare earth element is Dy. As shown in FIG. 10, it was found that the distribution ratio of each rare earth element increases as the concentration of the common anion species increases.

In addition, in other words, the above-mentioned result is that even if resources are eluted using an aqueous phase solution containing mineral acid (HCl) in the elution step, the aqueous phase solution On the other hand, if the hydrophobic anion species capable of constituting the ionic liquid is added, it means that the distribution ratio of each rare earth element can be increased. In addition, if the added hydrophobic anion species is the same as the anion species of the organic phase solution, the rare earth element can be efficiently recovered.
That is, even when a mineral acid is used in the elution step, the rare earth element can be efficiently recovered, and the range of types of substances that can be used in the aqueous phase solution can be expanded.

  An example corresponding to [Embodiment 3] will be described below.

<Example 8> (Recovery of Nd and Dy from actual waste VCM employing a normal extraction process and a reverse extraction process)
In this example, the test was performed according to the flowchart shown in FIG. The 1-A) disassembly / sorting step to 1-E) elution step were the same as in <Example 1>. Further, items not specifically mentioned below were the same as those in <Example 1>. In addition, about the codes | symbols, such as 1-A) and 1-B), the code | symbol based on [Embodiment 3] is used. In addition, the organic phase solution and the aqueous phase solution used in the normal extraction step and the reverse extraction step of this example are simply “organic” in order to distinguish them from the organic phase solution and aqueous phase solution that existed before both steps. Phase ”and“ Aqueous phase ”.

First, in the 1-F) deironing step, as described in the above embodiment, a treatment for avoiding coprecipitation of divalent Fe ions and rare earth elements was performed. Specifically, by adding calcium hydroxide to the aqueous phase solution until the pH of the aqueous phase solution is 4.75, oxygen bubbling is performed for 2 hours at a flow rate of 1.5 L / min. Fe was oxidized to trivalent ions. The absence of divalent Fe ions in the aqueous phase solution was confirmed using a 1,10-phenanthroline indicator. As a result, a precipitate of [Fe (OH) _x ] ^3-x was formed in the aqueous phase solution. After the polymer flocculant was administered to the precipitate, it was removed by suction filtration and a deironing step was performed.
In addition, as a result of analyzing the obtained solution by ICP-AES, it confirmed that Fe was 0 ppm and the iron removal rate was 100%.

なお、表中のＲＥは希土類種Ｐｒ，Ｎｄ，Ｄｙの合計値を示す。 TODGA (N, N, N ′, N′-tetraoctyl diglycolamide) was synthesized by the following procedure before the extraction and separation step. When the reaction of diglycolyl chloride and dioctylamine was allowed to proceed at a molar ratio of 1: 2 in a diethyl ether solvent, the reaction was performed by adding diglycolyl chloride dropwise to a mixture of dioctylamine and triethylamine. Although an exothermic reaction is accompanied at the time of dropping, the reaction bath is circulated and cooled, so that all of the diglycolyl chloride is dropped in a state where the temperature range of 0 to 5 ° C. is maintained, and then the reaction proceeds under conditions of 300 rpm and 36 hours. I let you. The white hardly soluble substance generated during the reaction was separated into solid and liquid, and then the organic phase (TODGA in diethyl ether) was collected. 100 ml of 0.1N hydrochloric acid was added to the organic phase, and centrifugation was performed under conditions of 9840 G for 5 minutes to wash the organic phase. Thereafter, the solvent in the organic phase was completely removed by being kept in a draft under conditions of 100 ° C., 500 rpm, 24 hours. Finally, dehydrated TODGA was obtained by vacuum drying at 100 ° C. for 48 hours. The synthesis yield was 94.2%.
In the 1-Ga) normal extraction step, which is the extraction and separation step, the extractant (TODGA) collected at a concentration of 0.1 M is dissolved in the diluent: [P ₂₂₂₅ ] [TFSA]. 4 ml of organic phase was prepared. Then, 6.4 ml (0.16M HTFSA solution, pH = 1.00) of the aqueous phase solution after the deironation step was added to the organic phase with the precipitate forming agent Ca (OH) ₂ . The mixture was stirred at 25 ° C. and 9840 G for 5 minutes. After standing, the phases were separated and the aqueous phase was removed, and then the 1-Gb) back extraction step was performed. In the back extraction step, 6.4 ml of nitric acid (concentration 0.01M, pH = 2.80) was prepared as an aqueous phase and mixed with 6.4 ml of the organic phase after the first normal extraction step. The mixture was stirred at 25 ° C. and 9840 G for 5 minutes. After standing, phase separation was performed to remove the aqueous phase, and then a second positive extraction step was performed. The second positive extraction step was the same as the first positive extraction step. Specifically, first, the rare earth species is eluted from the actual waste, and then the 0.16M HTFSA solution after the deironation process is performed with the precipitation forming agent Ca (OH) _{2 is} used as the aqueous phase. Mixed with organic phase. The extraction conditions were the same as those in the first positive extraction step, and the mixture was stirred at 25 ° C., 9840 G for 5 minutes. After standing, phase separation was performed to remove the aqueous phase, and then a second back extraction step was performed. In the second back extraction step, 6.4 ml of nitric acid (concentration 0.01 M) was prepared as an aqueous phase in the same manner as in the first back extraction step, and mixed with 6.4 ml of the organic phase after the second forward extraction step. The back extraction conditions are the same as the first time. Similarly, the third normal extraction step and the back extraction step were performed. Tables 7 and 8 show the extraction rate of each element and the metal concentration results in the organic phase. Table 7 shows the distribution ratio of the rare earth element after extraction measured for each number of extractions = the rare earth element concentration in the organic phase / the rare earth element concentration in the water phase.

In the table, RE indicates the total value of rare earth species Pr, Nd, Dy.

As is apparent from Table 7, in the first positive extraction step, the extraction rate of rare earth species was 96% or more, and the rare earth species could be extracted efficiently. Here, although the extraction rate of Ca was a low value of 12.0%, the rare earth species was eluted from the actual waste, and the deironation process was performed with the precipitation forming agent Ca (OH) ₂ . Since the Ca concentration was higher than that of the rare earth species, as shown in Table 8, the Ca concentration in the organic phase was 13.3 mM, which was higher than Pr and Dy.

  Next, in the first back extraction step, the back extraction rate of rare earth species was 1.0% or less, indicating that the rare earth species were not back extracted on the water phase side. On the other hand, the back extraction rate of Ca was a very high value of 83.4%, and it was confirmed that the Ca concentration in the organic phase was reduced to 2.21 mM.

  The rare earth concentrations in the first normal extraction step and back extraction step were almost unchanged at 23.58 mM and 23.46 mM, and the Ca concentration could be reduced from 13.3 mM to 2.21 mM. That is, it has been clarified that Ca can be selectively removed in the back extraction process.

  In addition, since the extractant TODGA recovers the extraction ability corresponding to the volume of Ca released to the aqueous phase after the back extraction process, the second normal extraction process is possible. Here, in the second positive extraction step, the extraction rate from the TODGA extraction mechanism to dilute Dy is relatively high at 76.8%, and the Ca extraction rate is suppressed to 4.7%. It was possible to increase the rare earth concentration and suppress the Ca concentration lower than after the positive extraction step.

  Similarly, by performing the third back extraction step, the back extraction rate of Ca was 100%, and Ca could be completely separated to the water phase side. Finally, the organic phase obtained after the third back-extraction step contained 23.60 mM rare earth species.

The extraction mechanism during the positive extraction process is as follows.
When [RE ³⁺ ] _aq and [Ca ²⁺ ] _aq are present alone in the aqueous phase, although not shown in the figure, it became clear that the extraction mechanism of TODGA proceeds as follows. Here, RE = Pr, Nd, and Dy are shown.
[RE ³⁺ ] _aq +3 [TODGA] _IL +3 [P ₂₂₂₅ ] [TFSA] _IL ⇔ [RE (TODGA) ₃ (TFSA) ₃ ] _IL +3 [P ₂₂₂₅ ⁺ ] _aq
[Ca ²⁺ ] _aq +2 [TODGA] _IL +2 [P ₂₂₂₅ ] [TFSA] _IL ⇔ [Ca (TODGA) ₂ (TFSA) ₂ ] _IL +2 [P ₂₂₂₅ ⁺ ] _aq
That is, it was a cation exchange extraction mechanism that proceeds at a molar ratio of [RE ³⁺ ] _aq : [TODGA] _IL = 1: 3, [Ca ²⁺ ] _aq : [TODGA] _IL = 1: 2.

On the other hand, in the solution obtained by performing the iron removal step with the precipitation forming agent Ca (OH) _{2 with} respect to the amide solution from which the actual waste is eluted, the concentration in the aqueous phase is [RE ³⁺ ] _aq << [Ca ²⁺ ] Since it is _aq , the extraction-mechanism analysis result (logD-log [TODGA] _IL ) under this density | concentration condition was shown in FIG. Since the stoichiometric coefficient for the rare earth species is 2.0 and the stoichiometric coefficient for Ca is 1.0 from the slope of the straight line in each metal species, it can be expressed by the following extraction equilibrium equation. did it.
[RE ³⁺ ] _aq + [Ca ²⁺ ] _aq +3 [TODGA] _IL +5 [P ₂₂₂₅ ] [TFSA] _IL ⇔ [RE (TODGA) ₂ (TFSA) ₃ ] _IL + [Ca (TODGA) (TFSA) ₂ ] _IL +5 [P ₂₂₂₅ ⁺ ] _aq
That is, in the rare earth mixed system with a high Ca concentration, the stoichiometric coefficient of TODGA with respect to Ca is lower than that with a system in which Ca is present alone, so that the complex formation state of Ca ²⁺ with respect to TODGA of the tridentate ligand is It became weak and became a factor that the extraction rate at the time of positive extraction decreased. Similarly, the weak Ca ²⁺ complexing state was determined to be a factor that is easily extracted back to the aqueous phase.

After the third back-extraction step, in order to use the extracted sample as an electrolytic bath, vacuum drying treatment was performed in an oil bath bath under conditions of 110 ° C., 300 rpm, and 24 hours. The amount of moisture in the organic phase after vacuum drying was measured with a Karl Fischer moisture meter with a moisture vaporizer, and found to be 62 ppm. The electrochemical measurement result at 120 ° C. of the extracted sample is shown in FIG. In FIG. 13, the TODGA / [P ₂₂₂₅ ] [TFSA] system in which the same concentration of the extractant is dissolved in the diluent is not subjected to the normal extraction process and the reverse extraction process, but only the vacuum drying process using an oil bath is performed. The electrochemical behavior of the solution (dashed line) is shown as a comparison.
In the electrochemical behavior of TODGA / [P ₂₂₂₅ ] [TFSA] before extraction indicated by a one-dot chain line, no peak current is observed on the reduction side, and a reduction current corresponding to the potential window on the cathode side from around −3.16 V is observed. It was observed. On the other hand, a remarkable reduction peak was observed at −2.63 V in the rare earth extraction medium that was vacuum-dried after the third back extraction step. This indicated the following reduction reaction.
[Nd (TODGA) ₂ ] ³⁺ + 3e ⁻ → Nd (0) +2 [TODGA]
That is, it was suggested that Nd metal could be deposited by direct electrodeposition from the extraction medium after the third back extraction step.

表９に示した通り、第一電解析出工程ではＮｄ濃度が比較的高い電析物が得られた。また、第二電解析出工程ではＤｙのモル比率が高い電析物が得られた。 <Example 9>
In this example, the set of the normal extraction process and the reverse extraction process in Example 8 was performed five times, and then the rare earth element electrolytic deposition was actually performed. Specifically, in this example, the same continuous extraction process as in Example 8 was performed under the following conditions to prepare 19.2 ml of an extraction medium for an electrolytic deposition test. The acid medium in the first positive extraction step was 0.24 M HTFSA solution (pH = 0.83) or 0.32 M HTFSA solution (pH = 0.71). As the aqueous phase in the positive extraction step, a solution obtained by elution of rare earth species from the actual waste as in Example 8 and then deironing using the precipitation forming agent Ca (OH) ₂ was used. The aqueous phase in the back extraction step used 0.01 M nitric acid as in Example 8. Finally, an organic phase TODGA / [P ₂₂₂₅ ] [TFSA] with Pr = 4.31 mM, Nd = 26.6 mM, Dy = 1.63 mM and Ca = 0.01 mM is obtained after the fifth back extraction step. It was. The vacuum drying conditions were the same as in Example 8, and the water content in the organic phase was 41 ppm.
In the 1-Ha) anode elution step and 1-Hb) first electrolytic deposition step, this organic phase was used as an electrolytic bath. Nd-Fe-Brod separated by a Vycor glass filter was used for the anode, and a Cu substrate was used for the cathode. A Pt line was used as a pseudo reference electrode. An Nd electrodeposition test was performed under the conditions of an electrolytic bath temperature: 100 ° C., an electrolytic atmosphere: Ar, an applied voltage: −3.35 V, and a total electric quantity: 31.8 C. The anode current efficiency was 89.7%, the cathode deposit was 9.6 mg, and the cathode current efficiency was 60.4% when it was assumed that the electrodeposit was composed only of Nd.
FIG. 14 is a graph showing the results of XPS analysis of the electrodeposit obtained in Example 9. As a result, in the Nd3d _5/2 spectrum, a peak of 981.8 eV was prominent at a depth of 0.2 μm from the outermost surface layer, which was an intermediate state between the oxide phase and the metal phase. On the other hand, a peak of 980.7 eV was prominent at a depth of 1.2 μm from the outermost surface layer, confirming the formation of a metal phase.
After carrying out the first electrolytic deposition step and pulling up all the electrode members, 1-Hc) the second electrolytic deposition step was carried out. The electrode configuration used was Dy rod for the anode and a Cu substrate for the cathode. A Pt line was used as a pseudo reference electrode. The Dy electrodeposition test was conducted under the conditions of electrolytic bath temperature: 100 ° C., electrolytic atmosphere: Ar, applied voltage: −3.76 V, and total electric quantity: 10.6C. The anode current efficiency was 80.3%, the cathode deposit was 2.7 mg, and the cathode current efficiency was 50.8% when the electrodeposit was assumed to be composed only of Dy.
The cathode deposit in each electrolytic deposition process was analyzed by EDX. The results are shown in Table 9.

As shown in Table 9, an electrodeposit having a relatively high Nd concentration was obtained in the first electrolytic deposition step. In the second electrolytic deposition step, an electrodeposit having a high Dy molar ratio was obtained.

DESCRIPTION OF SYMBOLS 1 ... Electrolytic test apparatus, 2 ... Anode part, 3 ... Glass member, 4 ... Cathode part, 5 ... Reference electrode part, 6 ... Electrolytic cell, 7 ... Heat-resistant wool, 8 ... Mantle heater, 9 ... Hot stirrer, 10 ... Stirrer, 11 ... Silicon plug, 12 ... Thermocouple, 13 ... Glass filter, 14 ... Organic phase solution after extraction (electrolytic bath), 15 ... Organic phase solution after extraction (anode side)

Claims (14)

In the method for recovering rare earth elements using ionic liquid, the rare earth elements are recovered from resources containing iron group elements, boron and rare earth elements by electrolytic deposition of rare earth elements.
An elution step of eluting iron group elements, boron and rare earth elements from the resources into an aqueous phase solution;
Extraction that selectively extracts rare earth elements from the iron group elements, boron, and rare earth elements in the aqueous phase solution into an organic phase solution that can be used as an electrolytic bath for electrolytic deposition after the elution step. A separation process;
After the extraction and separation step, using the organic phase solution as an electrolytic bath, an electrolytic deposition step of electrolytically depositing a rare earth element from the organic phase solution;
A method for recovering a rare earth element using an ionic liquid, comprising:
However, the aqueous phase solution is an acid solution containing a hydrophobic anion species capable of constituting an ionic liquid, and the organic phase solution contains an ionic liquid and a solvating extractant.   The method for recovering a rare earth element using an ionic liquid according to claim 1, wherein the hydrophobic anionic species in the aqueous phase solution and the anionic species constituting the ionic liquid in the organic phase solution are the same type. . A deironing step of separating the goethite from the aqueous phase solution by generating goethite as iron oxyhydroxide in the aqueous phase solution during the elution step and before the extraction and separation step. The method for recovering rare earth elements using ionic liquid according to claim 1 or 2 , further comprising: The method for recovering a rare earth element using an ionic liquid according to claim 3 , wherein the pH of the organic phase solution is more than 0.5 and not more than 5.0 in the extraction and separation step. In the iron removal step, the goethite is precipitated by adding a hydroxide of an alkali metal element or alkaline earth metal element to the aqueous phase solution, and the goethite is separated from the aqueous phase solution,
The organic phase solution, according to claim 3 or 4, characterized in that an iron element, a solution can be extracted selectively rare earth elements from among boron and plus an alkali metal element or alkaline earth element in the rare earth element A method for recovering rare earth elements using an ionic liquid as described in 1. 3. The method for recovering a rare earth element using an ionic liquid according to claim 1, wherein the pH of the organic phase solution is 0.5 or less in the extraction and separation step. In the extraction / separation step, when the ratio (A / O) of the volume (A) of the aqueous phase solution to the volume (O) of the organic phase solution is 1.0, the concentration of the solvating extractant is 1. The method for recovering a rare earth element using an ionic liquid according to any one of claims 1 to 6 , wherein the method is 23M or more and 2.15M or less. In the extraction and separation step, when the concentration of the solvating extractant is 1.84 M, the ratio (A / O) of the volume (A) of the aqueous phase solution to the volume (O) of the organic phase solution is 0. The method for recovering a rare earth element using an ionic liquid according to any one of claims 1 to 6 , wherein the value is 5 or more and 1.0 or less. The method for recovering a rare earth element using an ionic liquid according to any one of claims 1 to 8 , wherein the iron group element is at least iron. The rare earth element recovered in the electrolytic deposition step is one or more selected from lanthanum element, cerium element, praseodymium element, neodymium element, samarium element, europium element, gadolinium element, terbium element and dysprosium element. The method for recovering a rare earth element using an ionic liquid according to any one of claims 1 to 9 , wherein the element is an element. In the method for recovering rare earth elements using ionic liquid, the rare earth elements are recovered from resources containing iron, boron and rare earth elements by electrolytic deposition of rare earth elements.
An elution step of eluting iron, boron and rare earth elements from the resources into an aqueous phase solution that is an amide solution ;
Deironing to separate the goethite from the aqueous phase solution by adding a hydroxide of an alkali metal element or alkaline earth metal element to the aqueous phase solution to produce goethite that is iron oxyhydroxide. Process,
A positive extraction step of selectively extracting rare earth elements among boron and rare earth elements in the aqueous phase solution after the deironation step into an organic phase solution that can be used as an electrolytic bath used in electrolytic deposition; ,
After the positive extraction step, the alkali metal element or an alkaline earth metal element was added in the deferrisation step, a back extraction step for selectively extracting from the organic phase solution to dilute mineral acids than the amide solution,
After the back extraction step, using the organic phase solution as an electrolytic bath, an electrolytic deposition step of electrolytically depositing a rare earth element from the organic phase solution;
A method for recovering a rare earth element using an ionic liquid, comprising:
However, the aqueous phase solution is an acid solution containing a hydrophobic anion species capable of constituting an ionic liquid, and the organic phase solution contains an ionic liquid and a diglycolamide type solvating extractant. The amide solution is an acid solution containing a hydrophobic anion species capable of constituting an ionic liquid and a solution containing an amide. The hydroxide of the alkaline earth metal element was added in deferrisation process is calcium hydroxide, the mineral acid used in the inverse extraction process of claim 1 1, characterized in that the nitrate ion A method for recovering rare earth elements using liquids. A calcium hydroxide production step for producing calcium hydroxide by mixing alkali with nitric acid after the back extraction step;
Further comprising
In the iron removal step, the calcium hydroxide obtained in the calcium hydroxide production step and the aqueous phase solution are mixed to produce and precipitate goethite through the hydroxide, and then separated from the aqueous phase solution. claim 1 2 according to the recovery method of rare earth element by using an ionic liquid which is characterized in that. The prior electrolytic deposition process, according to any one of claims 1 1 to 1 3, characterized in that it has a continuous extraction process repeated said positive extraction step and the stripping step are alternately, an ionic liquid Rare earth element recovery method used.

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