US20150047469A1 - Method for Recovering Rare Earth from Rare Earth Element-Containing Alloy - Google Patents
Method for Recovering Rare Earth from Rare Earth Element-Containing Alloy Download PDFInfo
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- US20150047469A1 US20150047469A1 US14/384,046 US201314384046A US2015047469A1 US 20150047469 A1 US20150047469 A1 US 20150047469A1 US 201314384046 A US201314384046 A US 201314384046A US 2015047469 A1 US2015047469 A1 US 2015047469A1
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- Prior art keywords
- rare earth
- earth element
- recovering
- electrolyte
- electrolysis
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 113
- 238000000034 method Methods 0.000 title claims abstract description 38
- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 18
- 239000000956 alloy Substances 0.000 title claims abstract description 18
- 150000002910 rare earth metals Chemical class 0.000 title description 31
- 239000003792 electrolyte Substances 0.000 claims abstract description 33
- 238000005868 electrolysis reaction Methods 0.000 claims abstract description 29
- 229910052751 metal Inorganic materials 0.000 claims abstract description 20
- 239000002184 metal Substances 0.000 claims abstract description 20
- 239000000843 powder Substances 0.000 claims abstract description 18
- 150000003839 salts Chemical class 0.000 claims description 8
- 238000002425 crystallisation Methods 0.000 claims description 6
- 238000000638 solvent extraction Methods 0.000 claims description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 20
- 239000000243 solution Substances 0.000 description 19
- 238000010828 elution Methods 0.000 description 12
- 229910052692 Dysprosium Inorganic materials 0.000 description 11
- 229910052779 Neodymium Inorganic materials 0.000 description 11
- 239000002253 acid Substances 0.000 description 10
- 229910052777 Praseodymium Inorganic materials 0.000 description 9
- -1 hydrofluoric acid ion Chemical class 0.000 description 8
- 229910052742 iron Inorganic materials 0.000 description 8
- 229910001172 neodymium magnet Inorganic materials 0.000 description 8
- 239000000706 filtrate Substances 0.000 description 6
- 238000002386 leaching Methods 0.000 description 6
- 238000011084 recovery Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 4
- 239000002244 precipitate Substances 0.000 description 4
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 229960004887 ferric hydroxide Drugs 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 229910052500 inorganic mineral Inorganic materials 0.000 description 3
- IEECXTSVVFWGSE-UHFFFAOYSA-M iron(3+);oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Fe+3] IEECXTSVVFWGSE-UHFFFAOYSA-M 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000011707 mineral Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 3
- 229910052938 sodium sulfate Inorganic materials 0.000 description 3
- 235000011152 sodium sulphate Nutrition 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- DUENOCOQRLXLKT-UHFFFAOYSA-N 5,8-diethyldodecan-6-ylphosphonic acid Chemical compound CCCCC(CC)CC(P(O)(O)=O)C(CC)CCCC DUENOCOQRLXLKT-UHFFFAOYSA-N 0.000 description 2
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- 150000003863 ammonium salts Chemical class 0.000 description 2
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 2
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 2
- 235000011130 ammonium sulphate Nutrition 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- KPLQYGBQNPPQGA-UHFFFAOYSA-N cobalt samarium Chemical compound [Co].[Sm] KPLQYGBQNPPQGA-UHFFFAOYSA-N 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 239000005416 organic matter Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 229910000938 samarium–cobalt magnet Inorganic materials 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- PAWQVTBBRAZDMG-UHFFFAOYSA-N 2-(3-bromo-2-fluorophenyl)acetic acid Chemical compound OC(=O)CC1=CC=CC(Br)=C1F PAWQVTBBRAZDMG-UHFFFAOYSA-N 0.000 description 1
- 229910000521 B alloy Inorganic materials 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910052689 Holmium Inorganic materials 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 229910052771 Terbium Inorganic materials 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 229910000828 alnico Inorganic materials 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 235000019270 ammonium chloride Nutrition 0.000 description 1
- 230000003466 anti-cipated effect Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 230000005294 ferromagnetic effect Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-N hydrofluoric acid Substances F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910000765 intermetallic Inorganic materials 0.000 description 1
- 230000005291 magnetic effect Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 235000006408 oxalic acid Nutrition 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 235000002639 sodium chloride Nutrition 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B59/00—Obtaining rare earth metals
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09B—DISPOSAL OF SOLID WASTE
- B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
- B09B3/80—Destroying solid waste or transforming solid waste into something useful or harmless involving an extraction step
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
- C22B3/045—Leaching using electrochemical processes
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
- C22B3/06—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic acid solutions, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions
- C22B3/08—Sulfuric acid, other sulfurated acids or salts thereof
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B5/00—General methods of reducing to metals
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
- C22B7/006—Wet processes
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
- C25C1/06—Electrolytic production, recovery or refining of metals by electrolysis of solutions or iron group metals, refractory metals or manganese
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
- C25C7/06—Operating or servicing
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Definitions
- a neodymium magnet is normally configured from a ferromagnetic Nd 2 Fe 14 B intermetallic compound as its main phase, a nonmagnetic B-rich phase, a nonmagnetic Nd-rich phase, and oxides and the like as impurities.
- efforts for improving the magnetic properties are being exerted by adding various types of elements thereto.
- Patent Document 3 describes a method of immersing a rare earth-transition metal alloy scrap in a mineral acid ammonium salt aqueous solution, circulating gas containing oxygen therein to oxidize the scrap and obtain a precipitate containing a powder of oxide and hydroxide, separating the precipitate from the mineral acid ammonium salt aqueous solution, and recovering a rare earth element from the separated precipitate.
- Patent Document 4 describes placing a rare earth oxide scrap in a molten salt electrolytic bath, melting and separating the scrap into rare earth oxide and a magnet alloy part in the electrolytic bath, reducing the rare earth metal by electrolyzing the rare earth oxide that was melted in the electrolytic bath, alloying the magnet alloy part with the rare earth metal, and thereby recycling the product as a rare earth metal-transition metal-boron alloy.
- Patent Document 5 describes using a rare earth element-containing alloy as a positive electrode, depositing the alloys of Co, Ni, and Fe on a negative electrode based on the direct electrolysis method and adding oxalic acid to an electrolyte containing a rare earth element so as to precipitate and separate oxalate, and burning this in the atmosphere so as to separate and recover the rare earth element.
- Patent Document 2 Japanese Patent Application Publication No. S62-83433
- Patent Document 3 Specification of Japanese Patent No. 4287749
- a rare earth element can be extremely easily and efficiently recovered by mixing a metal powder of a rare earth element-containing alloy with an electrolyte, and performing electrolysis in the electrolyte.
- the present invention provides:
- the present invention provides a superior method of being able to extremely easily and efficiently recover a rare earth element; specifically, a rare earth element can be recovered simply by performing electrolysis in an electrolyte which contains a metal powder of a rare earth element-containing alloy obtained from scraps such as spent permanent magnets or end materials that arise during manufacture.
- the recovery method of the present invention can be applied to a known rare earth magnet so as long as it is a rare earth permanent magnet, and there is no particular limitation in the component composition thereof.
- a known rare earth magnet there is, for example, a Nd—Fe—B-based rare earth permanent magnet, and this permanent magnet typically has Nd, Fe, and B as its components, and additionally contains, as needed, rare earth elements such as Dy, Pr, Tb, Ho, and Sm, or transition metal elements such as Co, Cu, Cr, Ni, and Al.
- the metal powder of the rare earth element-containing alloy of the present invention can be obtained, for example, from end materials, i.e., scraps that arise during the manufacture of rare earth magnets. While the scraps may be used directly if they are fine as with pulverized powders or abrasive powders, preferably, a large scrap of a certain shape such as a spent permanent magnet is used after being finely pulverized. Moreover, the recovery method of the present invention may be applied even when a part of the metal powder is an oxide. Moreover, when the power contains organic matter, preferably, such organic matter is eliminated by burning the metal powder under an atmospheric atmosphere at a temperature of 200° C. or higher.
- This metal powder is mixed in an electrolyte, which is prepared by mixing electric conducting salt and pure water, and electrolysis is performed in the electrolyte.
- electric conducting salt used may be, for example, ammonium sulfate, ammonium nitrate, ammonium chloride, sodium chloride, or sodium sulfate.
- the electrodes stainless steel, Ti, graphite or the like is used as the negative electrode, and an insoluble anode or the like is used as the positive electrode.
- pH of the electrolyte is preferably adjusted to be between 2 and 8. This is because, when the pH is low (acidic), much Fe becomes eluted and the filterability of the residue becomes inferior, and when the pH is high (alkaline), the elution rate of the rare earth metal will deteriorate.
- the solution temperature of the electrolyte is preferably adjusted to be between 10 and 90° C. When the electrolysis temperature is less than 10° C., the elution rate of the rare earth metal will deteriorate, and, when the electrolysis temperature exceeds 90° C., electrolysis becomes difficult due to the evaporation of the electrolyte.
- electrolytic conditions described above may be suitably selected upon performing the electrolysis since the conditions will vary depending on the type, quality, amount and other factors of the material.
- the Dy concentration will rise and, upon rising to roughly 100 g/l (solubility), the sulfate of Dy becomes crystallized based on the subsequent heating treatment performed at 60° C. It is thereby possible to recover Dy simultaneously with Nd.
- the recovery rate of Dy was 70%.
- a rare earth-containing scrap (containing rare earth elements Nd, Dy, and Pr) containing Fe was subject to acid leaching using a large quantity of hydrochloric acid. Consequently, while the elution rate of Nd, Dy, and Pr was 70 to 80%, the elution rate of Fe was also 80%. In addition, with acid leaching, the filterability of the residue was exceedingly inferior, and the treatment of the eluted Fe also became a problem.
Abstract
A method for recovering a rare earth element from a rare earth element-containing alloy, wherein a rare earth element is eluted by performing electrolysis in an electrolyte which contains a metal powder of a rare earth element-containing alloy. An object of this invention is to provide a method for extremely easily and efficiently recovering a rare earth element.
Description
- The present invention relates to a method for recovering a rare earth element from a rare earth element-containing alloy.
- In recent years, permanent magnets are being applied to various fields pursuant to significant advances, and improvement of their performance and development of new devices are being conducted day by day. In particular, the widespread use of permanent magnets in the fields of IT (information technology), automobiles, household appliances and FA (factory automation) is dramatically increasing from the perspective of energy conservation and environmental countermeasures.
- Permanent magnets are used, for example, in voice coil motors of hard disk drives and optical pickup parts of DVD/CD in relation to personal computers, in micro speakers and vibration motors in relation to portable phones, and in various motors such as servo motors and linear motors in relation to household appliances and industrial devices. Moreover, over 100 permanent magnets are used in a single hybrid electric vehicle (HEV).
- As permanent magnets, known are Alnico magnets, Ferrite magnets, samarium-cobalt (SmCo) magnets, neodymium (NdFeB) magnets and the like. In recent years, the R&D of neodymium magnets is particularly active, and various efforts are being exerted for achieving higher performance of such neodymium magnets.
- A neodymium magnet is normally configured from a ferromagnetic Nd2Fe14B intermetallic compound as its main phase, a nonmagnetic B-rich phase, a nonmagnetic Nd-rich phase, and oxides and the like as impurities. In addition, efforts for improving the magnetic properties are being exerted by adding various types of elements thereto.
- Demands for neodymium magnets are expected to continue increasing significantly in light of their superior performance. Nevertheless, the rare earth metals such as Nd and Dy that are contained in a neodymium magnet entail problems in terms of supply of resources, and it is anticipated that the price of these metals will rise sharply as demands for rare earth metals increase. Thus, the development of techniques for recovering and separating rare earth metals from this kind of rare earth magnet is being actively conducted.
- For example, Patent Document 1 describes recovering a rare earth element by heating and airing a rare earth element-iron-containing alloy, thereafter generating rare earth element salt and dissolving the generated rare earth element salt in a filtrate via acid leaching using strong acid, and filtering and separating the rare earth element therefrom.
- Moreover, Patent Document 2 describes recovering a rare earth element by dissolving a rare earth element-iron-based magnet material in a mineral acid solution, subsequently adding a hydrofluoric acid ion-containing solution to precipitate and generate rare earth fluoride, and separating the precipitate.
- Moreover, Patent Document 3 describes a method of immersing a rare earth-transition metal alloy scrap in a mineral acid ammonium salt aqueous solution, circulating gas containing oxygen therein to oxidize the scrap and obtain a precipitate containing a powder of oxide and hydroxide, separating the precipitate from the mineral acid ammonium salt aqueous solution, and recovering a rare earth element from the separated precipitate.
- Moreover, Patent Document 4 describes placing a rare earth oxide scrap in a molten salt electrolytic bath, melting and separating the scrap into rare earth oxide and a magnet alloy part in the electrolytic bath, reducing the rare earth metal by electrolyzing the rare earth oxide that was melted in the electrolytic bath, alloying the magnet alloy part with the rare earth metal, and thereby recycling the product as a rare earth metal-transition metal-boron alloy.
- Moreover, Patent Document 5 describes using a rare earth element-containing alloy as a positive electrode, depositing the alloys of Co, Ni, and Fe on a negative electrode based on the direct electrolysis method and adding oxalic acid to an electrolyte containing a rare earth element so as to precipitate and separate oxalate, and burning this in the atmosphere so as to separate and recover the rare earth element.
- Patent Document 1: Japanese Patent Application Publication No. H5-14777
- Patent Document 2: Japanese Patent Application Publication No. S62-83433
- Patent Document 3: Specification of Japanese Patent No. 4287749
- Patent Document 4: Japanese Patent Application Publication No. 2002-60855
- Patent Document 5: Japanese Patent Application Publication No. S59-67384
- Conventionally, when a rare earth element is recovered from a rare earth magnet, acids such as hydrochloric acid, nitric acid, and sulfuric acid are used to leach the rare earth. Nevertheless, when this kind of acid leaching is performed, iron tends to become eluted, and, when the leaching rate of the rare earth is increased, the iron concentration in the leaching solution will rise, and there is a problem in that deironization cannot be performed favorably. Moreover, there is also a problem in that ferric hydroxide, which has inferior settleability and filterab extremely easilyility, is likely to be obtained. In addition, there is a problem in that a large quantity of acid needs to be used in order to dissolve the entire rare earth magnet.
- In order to resolve the foregoing problems, as a result of intense study, the present inventors discovered that a rare earth element can be extremely easily and efficiently recovered by mixing a metal powder of a rare earth element-containing alloy with an electrolyte, and performing electrolysis in the electrolyte.
- Based on the foregoing discovery, the present invention provides:
- 1) A method for recovering a rare earth element, wherein a rare earth element is eluted by performing electrolysis in an electrolyte which contains a metal powder of a rare earth element-containing alloy;
- 2) The method for recovering a rare earth element according to 1) above, wherein electric conducting salt is added to the electrolyte;
- 3) The method for recovering a rare earth element according to 1) or 2) above, wherein pH of the electrolyte is set between 2 and 8, and a solution temperature of the electrolyte is set between 10 and 90° C.;
- 4) The method for recovering a rare earth element according to any one of 1) to 3) above, wherein electrolysis is performed while agitating the electrolyte;
- 5) The method for recovering a rare earth element according to any one of 1) to 4) above, wherein a rare earth element is recovered from a solution to which a rare earth element was eluted; and
- 6) The method for recovering a rare earth element according to any one of 1) to 5) above, wherein a rare earth element is recovered, via a solvent extraction method or a crystallization method, from a solution to which a rare earth element was eluted.
- The present invention provides a superior method of being able to extremely easily and efficiently recover a rare earth element; specifically, a rare earth element can be recovered simply by performing electrolysis in an electrolyte which contains a metal powder of a rare earth element-containing alloy obtained from scraps such as spent permanent magnets or end materials that arise during manufacture.
- The present invention provides a method for recovering a rare earth element from a rare earth element-containing alloy, wherein a metal powder of a rare earth element-containing alloy contained in a permanent magnet or the like is mixed in an electrolyte, and, by performing electrolysis in the electrolyte, the rare earth element is eluted.
- The recovery method of the present invention can be applied to a known rare earth magnet so as long as it is a rare earth permanent magnet, and there is no particular limitation in the component composition thereof. As a known rare earth magnet, there is, for example, a Nd—Fe—B-based rare earth permanent magnet, and this permanent magnet typically has Nd, Fe, and B as its components, and additionally contains, as needed, rare earth elements such as Dy, Pr, Tb, Ho, and Sm, or transition metal elements such as Co, Cu, Cr, Ni, and Al.
- The metal powder of the rare earth element-containing alloy of the present invention can be obtained, for example, from end materials, i.e., scraps that arise during the manufacture of rare earth magnets. While the scraps may be used directly if they are fine as with pulverized powders or abrasive powders, preferably, a large scrap of a certain shape such as a spent permanent magnet is used after being finely pulverized. Moreover, the recovery method of the present invention may be applied even when a part of the metal powder is an oxide. Moreover, when the power contains organic matter, preferably, such organic matter is eliminated by burning the metal powder under an atmospheric atmosphere at a temperature of 200° C. or higher.
- This metal powder is mixed in an electrolyte, which is prepared by mixing electric conducting salt and pure water, and electrolysis is performed in the electrolyte. As the electric conducting salt, used may be, for example, ammonium sulfate, ammonium nitrate, ammonium chloride, sodium chloride, or sodium sulfate. Moreover, as the electrodes, stainless steel, Ti, graphite or the like is used as the negative electrode, and an insoluble anode or the like is used as the positive electrode.
- Here, pH of the electrolyte is preferably adjusted to be between 2 and 8. This is because, when the pH is low (acidic), much Fe becomes eluted and the filterability of the residue becomes inferior, and when the pH is high (alkaline), the elution rate of the rare earth metal will deteriorate. Moreover, in light of costs, the solution temperature of the electrolyte is preferably adjusted to be between 10 and 90° C. When the electrolysis temperature is less than 10° C., the elution rate of the rare earth metal will deteriorate, and, when the electrolysis temperature exceeds 90° C., electrolysis becomes difficult due to the evaporation of the electrolyte.
- However, the electrolytic conditions described above may be suitably selected upon performing the electrolysis since the conditions will vary depending on the type, quality, amount and other factors of the material.
- The present invention can cause rare earth elements to be eluted as ions by performing electrolysis in an electrolyte which contains a metal powder on the one hand, and cause metals such as iron to be eluted in the electrolyte and precipitated as ferric hydroxide, or cause a part thereof to be electrodeposited on a cathode, and thereby eliminate iron from the electrolyte on the other hand.
- In order to efficiently advance this kind of electro-chemical reaction, it is important that the metal powder comes into contact with the anode as much as possible. Accordingly, for example, it would be effective to increase the number of times that the metal powder comes into contact with the anode by agitating the electrolyte, or increase the contact area by enlarging the area of the anode.
- By eluting the obtained rare earth elements as ions, filtering the solution to which the rare earth elements were eluted and thereby separating the rare earth elements, and then subjecting the product to the solvent extraction method or the crystallization method, rare earth elements can be recovered.
- The solvent extraction method is a method where, by adding an organic solution with an extracting agent dissolved therein to a filtrate to which rare earth ions are eluted, the extracting agent and the rare earth ions form a complex and become extracted and separated in the organic solution. As the extracting agent, used may be, for example, 2-ethylhexyl-2-ethylhexyl-phosphonic acid.
- Meanwhile, the crystallization method is a method where only the rare earth sulfate is crystallized and separated from the solution by raising the solution temperature of the electrolyte of a sulfuric acid system (for instance, sodium sulfate or ammonium sulfate) since the solubility of the rare earth sulfate differs depending on the difference in temperature.
- The present invention is now explained with reference to the following Examples and Comparative Examples. Note that these Examples are merely exemplifications, and the present invention is not in any way limited thereby. In other words, the present invention is limited only based on the scope of its claims, and covers various modifications other than the Examples contained herein.
- A rare earth-containing scrap (containing rare earth elements Nd, Dy, and Pr) containing Fe was subject to slurrying with 1 L of pure water containing sodium chloride to obtain an electrolyte, and electrolysis was performed therein. The electrolytic conditions were as follows; namely, pH of 2 to 3, electrolysis temperature of 20° C., current of 10 A, and electrolysis time of 20 hours. Consequently, the elution rate of Nd was 95%, the elution rate of Dy was 98%, and the elution rate of Pr was 94%. Fe precipitated as ferric hydroxide.
- Subsequently, after the electrolysis was completed, the residue in the solution was filtered and eliminated, and the filtrate was subject to the solvent extraction method using an extracting agent of 2-ethylhexyl-2-ethylhexyl-phosphonic acid (manufactured by Daihachi Chemical Industry; Product name: “PC88A”) to separate the rare earth elements, and the rare earth elements of Nd, Dy, and Pr were thereby recovered. The recovery rate was 98%.
- According to the foregoing process, it was possible to efficiently recover the rare earth metals of Nd, Dy, and Pr from a rare earth-containing scrap, and also attain favorable filterability. In addition, it was possible to use the rare earth elements of Nd,
- Dy, and Pr as the raw material of a recycled permanent magnet.
- Note that, when the metal content weight in the scrap is A and the metal content weight in the residue after electrolysis is B, the elution rate (%) indicates the ratio in which the metal had eluted in the solution, and is calculated as follows: elution rate (%)=(A−B)/A×100 (hereinafter the same in the Examples and the
- Comparative Examples).
- A rare earth-containing scrap (containing rare earth elements Nd, Dy, and Pr) containing Fe was subject to slurrying with 1 L of pure water containing sodium sulfate to obtain an electrolyte, and electrolysis was performed therein. The electrolytic conditions were as follows; namely, pH of 4, electrolysis temperature of 20° C., current of 5 A, and electrolysis time of 20 hours. Consequently, the elution rate of Nd was 98%, the elution rate of Dy was 99%, and the elution rate of Pr was 95%. Fe had electrodeposited on a cathode.
- Subsequently, after the electrolysis was completed, the residue in the solution was filtered and eliminated to obtain a rare earth-containing filtrate. This filtrate was used, the rare earth-containing scrap was once again added thereto and subject to slurrying, electrolysis was performed once again under the same conditions as those described above, and the Nd concentration in the solution was raised to roughly 100 g/l (solubility).
- Subsequently, the residue in the solution was filtered and eliminated, the filtrate was heated to 60° C., the rare earth sulfate of Nd was crystallized, and the salt thereof was recovered. Here, the recovery rate was 69%. Note that, while the solution after crystallization still contains rare earths, since this solution can be used once again in an electrolytic cell, it could be said that the loss of rare earth ions is basically zero.
- Moreover, as a result of repeating the foregoing electrolysis, the Dy concentration will rise and, upon rising to roughly 100 g/l (solubility), the sulfate of Dy becomes crystallized based on the subsequent heating treatment performed at 60° C. It is thereby possible to recover Dy simultaneously with Nd. Here, the recovery rate of Dy was 70%.
- In addition, when this kind of filtering/electrolysis process is repeated, the Pr concentration will rise and, upon rising to roughly 130 g/l, the sulfate of Pr becomes crystallized based on the subsequent heating treatment performed at 60° C. It is thereby possible to also recover Pr together with Dy and Nd. Here, the recovery rate of Pr was 68%.
- According to the foregoing process, it was possible to efficiently recover the rare earth metals of Nd, Dy, and Pr from a rare earth-containing scrap, and also attain favorable filterability. In addition, it was possible to use the rare earth elements of Nd,
- Dy, and Pr as the raw material of a recycled permanent magnet.
- A rare earth-containing scrap (containing rare earth elements Nd, Dy, and Pr) containing Fe was subject to acid leaching using a large quantity of hydrochloric acid. Consequently, while the elution rate of Nd, Dy, and Pr was 70 to 80%, the elution rate of Fe was also 80%. In addition, with acid leaching, the filterability of the residue was exceedingly inferior, and the treatment of the eluted Fe also became a problem.
- The present invention yields a significant industrial advantage with respect to the point of being able to extremely easily and efficiently recover a rare earth element because, with the method of the present invention, a metal powder of a rare earth element-containing alloy obtained from scraps such as spent permanent magnets or end materials that arise during manufacture is used, and a rare earth element can be recovered simply by performing electrolysis in an electrolyte which contains the metal powder.
Claims (10)
1. A method for recovering a rare earth element, wherein a rare earth element is eluted by performing electrolysis in an electrolyte which contains a metal powder of a rare earth element-containing alloy.
2. The method for recovering a rare earth element according to claim 1 , wherein electric conducting salt is added to the electrolyte.
3. The method for recovering a rare earth element according to claim 2 , wherein pH of the electrolyte is set between 2 and 8, and a solution temperature of the electrolyte is set between 10 and 90° C.
4. The method for recovering a rare earth element according to claim 3 , wherein electrolysis is performed while agitating the electrolyte.
5. The method for recovering a rare earth element according to claim 4 , wherein a rare earth element is recovered from a solution to which a rare earth element was eluted.
6. The method for recovering a rare earth element according to claim 5 , wherein a rare earth element is recovered, via a solvent extraction method or a crystallization method, from a solution to which a rare earth element was eluted.
7. The method for recovering a rare earth element according to claim 1 , wherein pH of the electrolyte is set between 2 and 8, and a solution temperature of the electrolyte is set between 10 and 90° C.
8. The method for recovering a rare earth element according to claim 1 , wherein the electrolysis is performed while agitating the electrolyte.
9. The method for recovering a rare earth element according to claim 1 , wherein the rare earth element is recovered from a solution to which the rare earth element is eluted.
10. The method for recovering a rare earth element according to claim 1 , wherein the rare earth element is recovered, via a solvent extraction method or a crystallization method, from a solution to which the rare earth element was eluted.
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PCT/JP2013/068963 WO2014013929A1 (en) | 2012-07-19 | 2013-07-11 | Method for recovering rare earth from rare earth element-containing alloy |
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US14/384,046 Abandoned US20150047469A1 (en) | 2012-07-19 | 2013-07-11 | Method for Recovering Rare Earth from Rare Earth Element-Containing Alloy |
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US (1) | US20150047469A1 (en) |
EP (1) | EP2781623B1 (en) |
JP (1) | JP5647750B2 (en) |
KR (1) | KR20140108298A (en) |
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US10597771B2 (en) | 2014-10-27 | 2020-03-24 | Jx Nippon Mining & Metals Corporation | Rare earth thin-film magnet and method for producing same |
EP3795704A1 (en) * | 2019-09-17 | 2021-03-24 | Institut "Jozef Stefan" | A method for selective recovery of rare earth elements from nd-fe-b magnet scraps based on electrolysis |
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US11072842B2 (en) | 2016-04-15 | 2021-07-27 | Jx Nippon Mining & Metals Corporation | Rare earth thin film magnet and method for producing same |
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US10597771B2 (en) | 2014-10-27 | 2020-03-24 | Jx Nippon Mining & Metals Corporation | Rare earth thin-film magnet and method for producing same |
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CN113832348A (en) * | 2021-09-18 | 2021-12-24 | 内蒙古大学 | Method for recovering rare earth and cobalt elements from rare earth permanent magnet muddy waste |
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TW201413058A (en) | 2014-04-01 |
JP5647750B2 (en) | 2015-01-07 |
TWI567241B (en) | 2017-01-21 |
EP2781623B1 (en) | 2017-04-05 |
EP2781623A1 (en) | 2014-09-24 |
KR20140108298A (en) | 2014-09-05 |
CN104169471A (en) | 2014-11-26 |
WO2014013929A1 (en) | 2014-01-23 |
JPWO2014013929A1 (en) | 2016-06-30 |
EP2781623A4 (en) | 2015-11-11 |
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