EP2885436A1 - Recovery of rare earth metals - Google Patents

Recovery of rare earth metals

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Publication number
EP2885436A1
EP2885436A1 EP13879584.4A EP13879584A EP2885436A1 EP 2885436 A1 EP2885436 A1 EP 2885436A1 EP 13879584 A EP13879584 A EP 13879584A EP 2885436 A1 EP2885436 A1 EP 2885436A1
Authority
EP
European Patent Office
Prior art keywords
salt
melt
chloride
rem
aluminium
Prior art date
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.)
Withdrawn
Application number
EP13879584.4A
Other languages
German (de)
French (fr)
Other versions
EP2885436A4 (en
Inventor
Seshadri Seetharaman
Lidong Teng
Sridhar Seetharaman
Mansoor Barati
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
JERNKONTORET
Original Assignee
JERNKONTORET
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Filing date
Publication date
Application filed by JERNKONTORET filed Critical JERNKONTORET
Publication of EP2885436A1 publication Critical patent/EP2885436A1/en
Publication of EP2885436A4 publication Critical patent/EP2885436A4/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
    • C25C3/34—Electrolytic production, recovery or refining of metals by electrolysis of melts of metals not provided for in groups C25C3/02 - C25C3/32
    • 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
    • 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
    • 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

  • the invention relates to a process for recovering at least one rare earth metals (REM) from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu.
  • REM rare earth metals
  • Rare earth metals i.e. Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu
  • Nd containing magnets such as NdFeB -magnets
  • batteries such as battery cathodes containing AB5, where A is lanthanum, cerium, neodymium and/or praseodymium, and B is nickel, cobalt, manganese and/or aluminium, thin films, lightings and displays, ores, rare earth concentrates from ores.
  • the rare metals can be present in metallic form but commonly as oxides, e.g. La 2 0 3 , Ce0 2 , Pr 6 On, Nd 2 0 3 , Sm 2 0 3 , Eu 2 0 3 , Gd 2 0 3 , Tb 4 0 7 , Dy 2 0 3 , Ho 2 0 3 , Er 2 0 3 , Tm 2 0 3 , Yb 2 0 3 , Lu 2 0 3 , and Y 2 0 3 .
  • oxides e.g. La 2 0 3 , Ce0 2 , Pr 6 On, Nd 2 0 3 , Sm 2 0 3 , Eu 2 0 3 , Gd 2 0 3 , Tb 4 0 7 , Dy 2 0 3 , Ho 2 0 3 , Er 2 0 3 , Tm 2 0 3 , Yb 2 0 3 , Lu 2 0 3 , and Y 2 0 3 .
  • the object of the invention is to provide a process for recovering at least one rare earth metal from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu from a resource containing at least one of these metals.
  • Another object of the invention is to recover Nd and/or Dy from Nd/Dy containing magnets.
  • At least one of the objects mentioned above is met by a process for recovering at least one rare earth metals (REM) from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, said process including the steps of: a) providing a crucible for supporting a salt melt; b) providing a salt melt consisting of (in weight %):
  • a chloride salt composition consisting of at least two metal chlorides selected from the group consisting of chlorides of Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, and Ra, - optionally 0-10 of halides, additional chlorides, sulphides and/or oxides; c) providing at least one REM containing resource to the crucible before or after heating to form the salt melt, said REM containing resource including at least one rare earth metal from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; d) reacting the aluminium chloride as a chloride donor with at least one rare earth metal of the REM containing resource to form at least one rare earth metal chloride dissolved in the salt melt; e) optionally maintaining AICI3 levels by adding AICI3 stepwise or continuously as it is consumed or by in situ formation of A1C13 in
  • At least one rare earth metal from the group of: Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu can be recovered.
  • the salt melt is preferably heated under protective atmosphere, suitably argon.
  • the atmosphere may also be nitrogen.
  • chlorine gas may be admixed to the nitrogen or argon atmosphere.
  • the contents of the salts are within 10 % by weight from the lowest eutectic point of the salt combination, more preferably within 5% by weight , most preferably within 1 % by weight.
  • other contents may be used as long as the liquidus temperature of the salt combination is at least 50°C lower than the operating temperature during electrolyzing; preferably 100 °C lower than the operating temperature.
  • the salt composition comprises at least two of the salts selected from the group: NaCl, KCl, LiCl, and CaCl 2 , preferably at least three of the salts selected from the group: NaCl, KCl, LiCl, and CaC12.
  • the at least one chloride salt composition includes by weight % of the at least one chloride salt, 3-20 NaCl, 30-70 KCl, 20-60 LiCl, preferably 5-15 NaCl, 40-60 KCl, 30-50 LiCl, more preferably 7-12 NaCl, 45-55 KCl, 35-45 LiCl.
  • the at least one chloride salt composition includes by weight % of the at least one chloride salt, 10-50 NaCl, 2-20 KCl, 50-80 CaCl 2 preferably 25-35 NaCl, 3-10 KCl, 60-75 CaCl 2 .
  • the at least one chloride salt composition includes by weight % of the at least one chloride salt, 5-20 NaCl, 20-40 LiCl, 40-70 CaCl 2 preferably 7-15 NaCl, 25-35 LiCl, 50-60 CaCl 2 .
  • the at least one chloride salt composition includes by weight % of the salt composition, 35-65 KCl, 20-50 LiCl, 5-20 CaC12 preferably 45-55 KCl, 30-40 LiCl, 10-15 CaCl 2 .
  • the flux is A1C1 3 .
  • the flux can be added before or after forming the salt melt. It may also be added stepwise as it is consumed. In one embodiment at least a fraction up to all of the AICI3 is generated in situ by reacting chloride ions in the salt melt with an aluminium anode, preferably the aluminum anode is an aluminum melt at the bottom of the crucible.
  • the REM containing resource may be crushed and/or ground and/or milled before being provided to the crucible.
  • the crushed and/or ground and/or milled may be pelletized before being provided to the crucible.
  • the REM containing resource may e.g. be: - permanent magnets, in particular Nd and/or Dy containing magnets, preferably
  • NdFeB -magnets where Nd may be partially replaced by Dy.
  • the magnets may be coated with metallic zinc, nickel, nickel+nickel, copper+nickel,
  • the magnets may also include other metals such as Nb and Co. These metals may be selectively electrodeposited during electrolysis.
  • batteries preferably cathodes containing AB5, where A is lanthanum, cerium, neodymium and/or praseodymium, and B is nickel, cobalt, manganese and/or aluminium;
  • Rare earth oxides are particularly suitable, for instance rare earth oxides from the group of: La 2 0 3 , Ce0 2 , Pr 6 On, Nd 2 0 3 , Sm 2 0 3 , Eu 2 0 3 , Gd 2 0 3 , Tb 4 0 7 , Dy 2 0 3 , Ho 2 0 3 , Er 2 0 3 , Tm 2 0 3 , Yb 2 0 3 , Lu 2 0 3 , and Y 2 0 3 .
  • Resources of particular interest are those containing at least one of Dy, Nd, Pm, Sm, Ho, Er, Tm, Yb and Lu. At present the most interesting elements to recover are Dy and Nd since these elements may be present in high contents in permanent magnets.
  • the ocean floor nodule ore is excluded as a REM containing resource because said raw material normally has a very low content of rare earth oxides and since they contain high amounts of base metals such as Mn, Fe and Ni.
  • the flux A1C1 3 acts as a chloride donor dissolving rare earth metal oxides and/or rare earth metals to rare earth metal chlorides in the salt melt.
  • the following chlorides can be formed depending on which are earth oxides or metals that are present in the resource to be dissolved: LaCl 3 , CeCl 3 , PrCl 3 , NdCl 3 , SmCl 3 , EuCl 3 , GdCl 3 , TbCl 3 , DyCl 3 , HoCl 3 , ErCl 3 , TmCl 3 , YbCl 3 , LuCl 3 , and YC1 3 .
  • A1C1 3 dissolves rare earth metal oxides, aluminium will form A1 2 0 3 .
  • A1C1 3 dissolves rare earth metals, Al metal is released which will is highly reactive and is hence likely to react with other reducible chlorides in the salt melt.
  • the dissolving step d) is performed before the recovering step d). However they may in different embodiments partly or fully overlap as will be described below, in particular in relation to the use of a liquid aluminium anode.
  • the salt melt is kept at high temperature usually for a time between about 2 and about 10 hours, preferably 3-8 hours, more preferably 4-8 hours.
  • the amount of REM-containing resource is preferably such that a weight ratio
  • “flux'V'REM in the resource” is between 0.1-3, preferably 0.2-2.0, more preferably 0.3- 1.0, most preferably 0.4-0.6.
  • the temperature should be lower than 1000 °C, more preferably lower than 900 °C.
  • the temperature is preferably in the range of 550-700 °C during the dissolution, more preferably 580-650 °C.
  • the temperature of the salt melt is preferably at least 50 °C above the liquidus temperature of the salt melt, more preferably at least 100°C above the liquidus temperature of the salt melt.
  • Nd+ A1C1 3 Al+ NdCl 3
  • Neodymium can be recovered from neodymium chloride by electrolysis and/or vaporization.
  • the salt melt used for extraction may optionally be recycled.
  • the at least one rare earth metal and other metals can be selectively electro-deposited from the salt melt.
  • the process can be designed to be continuous by combining the two steps. Residues after processing, such as A1 2 0 3 , may be used for landfill, building construction or as a raw material for the refractory industry.
  • the salts can be recovered and reused.
  • the REM is recovered by electrolysis by having at least one anode and at least one cathode are connected to the salt melt.
  • the recovering includes the step of electrolyzing the salt melt to form at least one rare earth metal at the cathode.
  • at least one REM from the group Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu is selectively electrodeposited on the at least one cathode.
  • the electrolysis is done using conventional anode/s and cathode/s which is further described under "Electrolysis using conventional anode/s and cathode/s".
  • the electrolysis includes an aluminium anode which facilitates an in situ formation of an aluminium chloride. This is further described under "Dissolving and electrolysis using aluminium anode”.
  • a conventional anode and cathode configuration is used, e.g. at least one cathode and at least one anode submerged in the salt melt.
  • two electrodes e.g. of graphite
  • a DC source e.g. a DC source.
  • the theoretical decomposition voltage for MC1 3 , where M is a rare earth metal is around 2.5-3 V.
  • a voltage in the range of 2.5-5 V is used for the electrolysis, more preferably 3-4 V. If A1C1 3 remains in the salt melt it may be selectively electrodeposited or co-deposited with the rare earth metal on the cathode.
  • the flux can be added in a single batch or in several batches as the aluminium chloride is consumed, preferably 5-30% by weight of the salt mixture when added in a single batch, more preferably 5-20 % by weight of the mixture, most preferably 7-15 wt%. Since the flux is difficult to recover after the extraction process, it is desirable that there is no excessive addition of aluminium chloride.
  • the amount of AICI 3 is maintained at a sufficient level. This may be done by adding AICI 3 stepwise or continuously as it is consumed and/or by in situ formation of AICI 3 in the salt melt. In situ formation of AICI 3 is discussed under "Dissolving and electrolysis using aluminium anode".
  • the content of aluminium chloride in the salt melt is dependent on the material to be treated.
  • the AlC ⁇ /Nd-ratio is 2/1 considering the reaction set out above.
  • the amount of AICI 3 is controlled within ⁇ 7 %, preferably within ⁇ 5 % or within ⁇ 3%.
  • the electrolysis preferably is carried out in the crucible that holds the salt melt with the dissolved REM containing resource containing at least one rare earth metal from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
  • the temperature of the salt melt is preferably lower than 1000 °C, more preferably lower than 900 °C.
  • the temperature is preferably in the range of 550-700 °C, more preferably 580-650 °C.
  • the temperature of the salt melt is preferably at least 50 °C above the liquidus temperature of the salt melt, more preferably at least 100°C above the liquidus temperature of the salt melt.
  • the dissolving step and the electrolysis step may be performed separately or they may fully or partly overlap.
  • the at least rare earth metal of the group Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and optionally other dissolved metals can selectively be electrodeposited on the cathode. After depositing one metal the cathode can be removed and the metal deposited on the cathode can be extracted. To avoid interrupts of the electrolysis, another "clean" electrode can be submerged.
  • the salt melt may have a plurality of electrodes which one after the other is activated as a cathode while the former is deactivated. Thereby, the metals can be selectively deposited at individual electrodes.
  • the chloride salts of the salt melt may be recycled.
  • the residue after processing contains A1 2 0 3 and for instance other stable oxides such as Si0 2 , depending on the contents of the REM containing resource.
  • the residues may for instance be used for landfill, building construction or as a raw material for the refractory industry.
  • the at least one anode includes aluminium, preferably in the form of an aluminium melt provided at the bottom of the crucible.
  • the aluminium melt form the anode or a part of the anode, for instance by immersing an electrode, e.g. a graphite electrode, in the aluminium melt and connecting it to positive polarity during electrolysis.
  • the crucible is at least partly made in a conductive material being in contact with the aluminium melt, and connecting the crucible positive polarity during the electrolysis. Thereby, the crucible and the molten aluminium operate as an anode.
  • at least one cathode is still required during electrolysis, e.g.
  • the salt melt and the aluminium are heated to a temperature where both are in liquid phase.
  • the temperature of the salt melt is preferably at least 50 °C above the liquidus temperature of the salt melt, more preferably at least 100°C above the liquidus temperature of the salt melt.
  • the temperature should be at least 660 °C and not more than 1000 °C, preferably the temperature is in the range of 700-900 °C.
  • the initiating chloride donor is provided to start the reactions in the salt melt.
  • the initiating chloride donor may be aluminium chloride and/or at least one metal chloride that can be electrolyzed, i.e. so that chloride ions forms AICI 3 at the contact surface between the salt melt and the aluminium melt.
  • the initiating chloride donor includes a metal chloride of the same type as provided in the chloride salt composition, e.g. at least one metal chloride selected from the group consisting of chlorides of Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, and Ra.
  • a metal chloride of the same type as provided in the chloride salt composition e.g. at least one metal chloride selected from the group consisting of chlorides of Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, and Ra.
  • the initiating chloride donor includes aluminium chloride added to the mixture before heating it or to the salt melt, said aluminium chloride being added up to 20 % by weight of the salt mixture, preferably 1-15 % by weight, more preferably 5-10% by weight.
  • aluminium melt as the anode or part of the anode the steps dissolving and recovering by electrolysis are expedited simultaneously, preferably for at least 2 hours.
  • additional REM containing resource can be stepwise or continuously added to the salt melt.
  • the electrolysis and dissolving operation can for instance be performed for 2-8 hours; where after metals deposited at the cathode/s is collected, and the electrolysis can be restarted.
  • another "clean" electrode can be submerged.
  • the salt melt may have a plurality of electrodes which one after the other is activated as a cathode and while the former is deactivated. Thereby the metals can be selectively deposited at individual electrodes.
  • the voltage is suitably within the range of 2.5-5V, preferably 3-4 V.
  • the rare earth metal may be co-deposited with aluminum or they may be selectively electrodeposited.
  • the residue after processing may contain A1 2 0 3 and for instance other stable oxides such as Si0 2 , depending on the contents of the REM containing resource; in particular if the REM containing resource contains REM oxides A1 2 0 3 may form when chlorinating the REM oxides.
  • the residues may for instance be used for landfill, building
  • Al CI 3 /neodymium ratio was 2/1 and the AlC13/salt ratio was 20 wt%.
  • the whole mixture was weighted before each experiment.
  • the masses of the each material are shown in the table 1.
  • the powders were poured in an alumina crucible and the crucible was put in the vertical furnace.
  • the time to reach the target temperature which was 850 °C was about 6 hours. Then the graphite electrodes were dipped into the salt bath and the electrolysis was started. The voltage was first set on 4 but due to the high current it was decreased to 3.2 in order to avoid constant current condition. The saturation current of the equipment which was used in this experiment was 5. By fixing the voltage on 4 the current increased to 4.99 (saturation current). Hence the voltage was decreased to 3.2 V. The electrolysis was done during 5 hours.
  • the deposited layer contained over 40 % by weight of Nd and over 20 % by weight of Al.
  • the amount of Fe was below 5 % by weight. It should be noted that the essentially all Fe remained in the salt melt although the theoretical decomposition voltage of FeCl 3 is below 1 V. From the experiment it can be concluded that Nd can be recovered from the salt melt by electrolysis.

Abstract

The invention concerns a process for recovering at least one rare earth metal (REM) from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. A chloride salt melt is provided and aluminium chloride is used to chlorinate a REMcontaining resource. The REM can be recovered by electrolysis, vaporisation or hydrometallurgical methods.

Description

RECOVERY OF RARE EARTH METALS
TECHNICAL FIELD:
The invention relates to a process for recovering at least one rare earth metals (REM) from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu.
BACKGROUND
Rare earth metals (i.e. Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) are becoming increasingly important in today's society. It is therefore an increased demand in finding improved methods of extracting rare earth metals from various resources such as permanent magnets, in particular Nd containing magnets such as NdFeB -magnets, batteries such as battery cathodes containing AB5, where A is lanthanum, cerium, neodymium and/or praseodymium, and B is nickel, cobalt, manganese and/or aluminium, thin films, lightings and displays, ores, rare earth concentrates from ores. The rare metals can be present in metallic form but commonly as oxides, e.g. La203, Ce02, Pr6On, Nd203, Sm203, Eu203, Gd203, Tb407, Dy203, Ho203, Er203, Tm203, Yb203, Lu203, and Y203.
OBJECT OF THE INVENTION
The object of the invention is to provide a process for recovering at least one rare earth metal from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu from a resource containing at least one of these metals.
Another object of the invention is to recover Nd and/or Dy from Nd/Dy containing magnets.
DESCRIPTION OF THE INVENTION
At least one of the objects mentioned above is met by a process for recovering at least one rare earth metals (REM) from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, said process including the steps of: a) providing a crucible for supporting a salt melt; b) providing a salt melt consisting of (in weight %):
- 60-99 of a chloride salt composition consisting of at least two metal chlorides selected from the group consisting of chlorides of Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, and Ra, - optionally 0-10 of halides, additional chlorides, sulphides and/or oxides; c) providing at least one REM containing resource to the crucible before or after heating to form the salt melt, said REM containing resource including at least one rare earth metal from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; d) reacting the aluminium chloride as a chloride donor with at least one rare earth metal of the REM containing resource to form at least one rare earth metal chloride dissolved in the salt melt; e) optionally maintaining AICI3 levels by adding AICI3 stepwise or continuously as it is consumed or by in situ formation of A1C13 in the salt melt; f) recovering said at least one REM, preferably by electrolysing the salt melt and selectively electrodepositing at least one REM.
Thereby at least one rare earth metal from the group of: Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu can be recovered.
The salt melt is preferably heated under protective atmosphere, suitably argon. The atmosphere may also be nitrogen. Furthermore, chlorine gas may be admixed to the nitrogen or argon atmosphere.
Salt Composition
For given salt combination of the least two chloride salts, it is preferred that the contents of the salts are within 10 % by weight from the lowest eutectic point of the salt combination, more preferably within 5% by weight , most preferably within 1 % by weight. However, other contents may be used as long as the liquidus temperature of the salt combination is at least 50°C lower than the operating temperature during electrolyzing; preferably 100 °C lower than the operating temperature.
Preferably the salt composition comprises at least two of the salts selected from the group: NaCl, KCl, LiCl, and CaCl2, preferably at least three of the salts selected from the group: NaCl, KCl, LiCl, and CaC12. In preferred embodiment the at least one chloride salt composition includes by weight % of the at least one chloride salt, 3-20 NaCl, 30-70 KCl, 20-60 LiCl, preferably 5-15 NaCl, 40-60 KCl, 30-50 LiCl, more preferably 7-12 NaCl, 45-55 KCl, 35-45 LiCl. In an alternative embodiment the at least one chloride salt composition includes by weight % of the at least one chloride salt, 10-50 NaCl, 2-20 KCl, 50-80 CaCl2 preferably 25-35 NaCl, 3-10 KCl, 60-75 CaCl2.
In an alternative embodiment the at least one chloride salt composition includes by weight % of the at least one chloride salt, 5-20 NaCl, 20-40 LiCl, 40-70 CaCl2 preferably 7-15 NaCl, 25-35 LiCl, 50-60 CaCl2.
In an alternative embodiment the at least one chloride salt composition includes by weight % of the salt composition, 35-65 KCl, 20-50 LiCl, 5-20 CaC12 preferably 45-55 KCl, 30-40 LiCl, 10-15 CaCl2.
Flux
The flux is A1C13. The flux can be added before or after forming the salt melt. It may also be added stepwise as it is consumed. In one embodiment at least a fraction up to all of the AICI3 is generated in situ by reacting chloride ions in the salt melt with an aluminium anode, preferably the aluminum anode is an aluminum melt at the bottom of the crucible.
REM containing resource
The REM containing resource may be crushed and/or ground and/or milled before being provided to the crucible. The crushed and/or ground and/or milled may be pelletized before being provided to the crucible.
The REM containing resource may e.g. be: - permanent magnets, in particular Nd and/or Dy containing magnets, preferably
NdFeB -magnets where Nd may be partially replaced by Dy. The magnets may be coated with metallic zinc, nickel, nickel+nickel, copper+nickel,
nickel+copper+nickel,gold. These coatings may be selectively electrodeposited during electrolysis. The magnets may also include other metals such as Nb and Co. These metals may be selectively electrodeposited during electrolysis. - batteries, preferably cathodes containing AB5, where A is lanthanum, cerium, neodymium and/or praseodymium, and B is nickel, cobalt, manganese and/or aluminium;
- thin films;
- lightnings and displays;
- ores;
- rare earth concentrates from ores.
Rare earth oxides are particularly suitable, for instance rare earth oxides from the group of: La203, Ce02, Pr6On, Nd203, Sm203, Eu203, Gd203, Tb407, Dy203, Ho203, Er203, Tm203, Yb203, Lu203, and Y203. Resources of particular interest are those containing at least one of Dy, Nd, Pm, Sm, Ho, Er, Tm, Yb and Lu. At present the most interesting elements to recover are Dy and Nd since these elements may be present in high contents in permanent magnets.
According to a preferred embodiment the ocean floor nodule ore is excluded as a REM containing resource because said raw material normally has a very low content of rare earth oxides and since they contain high amounts of base metals such as Mn, Fe and Ni.
Dissolving
The flux A1C13 acts as a chloride donor dissolving rare earth metal oxides and/or rare earth metals to rare earth metal chlorides in the salt melt. The following chlorides can be formed depending on which are earth oxides or metals that are present in the resource to be dissolved: LaCl3, CeCl3, PrCl3, NdCl3, SmCl3, EuCl3, GdCl3, TbCl3, DyCl3, HoCl3, ErCl3, TmCl3, YbCl3, LuCl3, and YC13.
When A1C13 dissolves rare earth metal oxides, aluminium will form A1203. When A1C13 dissolves rare earth metals, Al metal is released which will is highly reactive and is hence likely to react with other reducible chlorides in the salt melt.
In one embodiment the dissolving step d) is performed before the recovering step d). However they may in different embodiments partly or fully overlap as will be described below, in particular in relation to the use of a liquid aluminium anode. To dissolve the REM-containing resource, the salt melt is kept at high temperature usually for a time between about 2 and about 10 hours, preferably 3-8 hours, more preferably 4-8 hours. The amount of REM-containing resource is preferably such that a weight ratio
"flux'V'REM in the resource" is between 0.1-3, preferably 0.2-2.0, more preferably 0.3- 1.0, most preferably 0.4-0.6. The temperature should be lower than 1000 °C, more preferably lower than 900 °C. For optimal economy, the temperature is preferably in the range of 550-700 °C during the dissolution, more preferably 580-650 °C. To improve viscosity of the salt melt, the temperature of the salt melt is preferably at least 50 °C above the liquidus temperature of the salt melt, more preferably at least 100°C above the liquidus temperature of the salt melt. When dissolving a neodymium magnet (Nd2Fei4B) the reactions can be:
Nd+ A1C13 = Al+ NdCl3
The Gibbs energy of neodymium chloride formation is negative, whereas the Gibbs energy for formation of FeCl3 and BC13 are positive. Therefore formation of NdCl3 is more feasible than that of FeCl3 and BC13. Neodymium can be recovered from neodymium chloride by electrolysis and/or vaporization.
Recovering
To recover the REM-resource from the melt various processes may be used. The salt melt used for extraction may optionally be recycled. Preferably the at least one rare earth metal and other metals can be selectively electro-deposited from the salt melt. However, it is also possible to use vaporization of the metal chlorides and condensing them, or leach the salt phase in water and extracting the metals as hydroxides by hydrometallurgy method. The process can be designed to be continuous by combining the two steps. Residues after processing, such as A1203, may be used for landfill, building construction or as a raw material for the refractory industry. The salts can be recovered and reused.
In a preferred embodiment, the REM is recovered by electrolysis by having at least one anode and at least one cathode are connected to the salt melt. In this embodiment the recovering includes the step of electrolyzing the salt melt to form at least one rare earth metal at the cathode. Preferably at least one REM from the group Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu is selectively electrodeposited on the at least one cathode. In one embodiment the electrolysis is done using conventional anode/s and cathode/s which is further described under "Electrolysis using conventional anode/s and cathode/s".
In the most preferred embodiment, the electrolysis includes an aluminium anode which facilitates an in situ formation of an aluminium chloride. This is further described under "Dissolving and electrolysis using aluminium anode".
Electrolysis using conventional anode/s and cathode/s
According to one embodiment a conventional anode and cathode configuration is used, e.g. at least one cathode and at least one anode submerged in the salt melt.
Preferably, two electrodes, e.g. of graphite, are immersed into the melt and connectable to a DC source. The theoretical decomposition voltage for MC13, where M is a rare earth metal is around 2.5-3 V. Preferably a voltage in the range of 2.5-5 V is used for the electrolysis, more preferably 3-4 V. If A1C13 remains in the salt melt it may be selectively electrodeposited or co-deposited with the rare earth metal on the cathode.
The flux, AICI3, can be added in a single batch or in several batches as the aluminium chloride is consumed, preferably 5-30% by weight of the salt mixture when added in a single batch, more preferably 5-20 % by weight of the mixture, most preferably 7-15 wt%. Since the flux is difficult to recover after the extraction process, it is desirable that there is no excessive addition of aluminium chloride.
Accordingly, it is preferable to have a careful control of the content of aluminium chloride in the salt melt. Moreover, as set out under "Dissolving" a sufficient amount of AICI3 in the melt is preferred in order to get a sufficient formation of REM-chlorides in the salt melt. Accordingly, in a preferred embodiment the amount of AICI3 is maintained at a sufficient level. This may be done by adding AICI3 stepwise or continuously as it is consumed and/or by in situ formation of AICI3 in the salt melt. In situ formation of AICI3 is discussed under "Dissolving and electrolysis using aluminium anode". The content of aluminium chloride in the salt melt is dependent on the material to be treated. For neodymium magnets (Nd2Fei4B) the AlC^/Nd-ratio is 2/1 considering the reaction set out above. In the example 20 wt.% AlC^was used. Preferably, the amount of AICI3 is controlled within ± 7 %, preferably within ± 5 % or within ±3%.
The electrolysis preferably is carried out in the crucible that holds the salt melt with the dissolved REM containing resource containing at least one rare earth metal from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
During electrolysis chloride ions will be attracted to the anode. With the use of a conventional anode/s, e.g. a graphite electrode/s, chlorine gas will form and evaporate from the salt melt. The chlorine gas is preferably recovered. Preferably the batch of melt is electrolyzed for 2 to 8 hours. During the electrolysis, the temperature of the salt melt is preferably lower than 1000 °C, more preferably lower than 900 °C. For optimal economy the temperature is preferably in the range of 550-700 °C, more preferably 580-650 °C. To improve viscosity of the salt melt, the temperature of the salt melt is preferably at least 50 °C above the liquidus temperature of the salt melt, more preferably at least 100°C above the liquidus temperature of the salt melt.
The dissolving step and the electrolysis step may be performed separately or they may fully or partly overlap.
The at least rare earth metal of the group Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and optionally other dissolved metals, can selectively be electrodeposited on the cathode. After depositing one metal the cathode can be removed and the metal deposited on the cathode can be extracted. To avoid interrupts of the electrolysis, another "clean" electrode can be submerged. Alternatively, the salt melt may have a plurality of electrodes which one after the other is activated as a cathode while the former is deactivated. Thereby, the metals can be selectively deposited at individual electrodes.
After recovering the at least one rare earth metal and possibly other metals, the chloride salts of the salt melt may be recycled. The residue after processing contains A1203 and for instance other stable oxides such as Si02, depending on the contents of the REM containing resource. The residues may for instance be used for landfill, building construction or as a raw material for the refractory industry.
Dissolving and electrolysis using aluminium anode
In a preferred embodiment the at least one anode includes aluminium, preferably in the form of an aluminium melt provided at the bottom of the crucible. The aluminium melt form the anode or a part of the anode, for instance by immersing an electrode, e.g. a graphite electrode, in the aluminium melt and connecting it to positive polarity during electrolysis. Alternatively, the crucible is at least partly made in a conductive material being in contact with the aluminium melt, and connecting the crucible positive polarity during the electrolysis. Thereby, the crucible and the molten aluminium operate as an anode. Of course at least one cathode is still required during electrolysis, e.g. one or more graphite electrode/s submerged in the salt melt. When using an aluminium melt at the bottom of the crucible as the anode or part of the anode, the salt melt and the aluminium are heated to a temperature where both are in liquid phase. To improve viscosity of the salt melt, the temperature of the salt melt is preferably at least 50 °C above the liquidus temperature of the salt melt, more preferably at least 100°C above the liquidus temperature of the salt melt. The temperature should be at least 660 °C and not more than 1000 °C, preferably the temperature is in the range of 700-900 °C.
During the electrolysis metals/s from metal chloride/s is deposited at the cathode. At the contact surface between the salt melt and the aluminium melt chloride ions are reacting with aluminium, thereby forming A1C13. This means that during steady state the salt melt can be wholly or partly self-supporting in regards of the flux, AICI3 and also that emission of chlorine gas is reduced. Lesser amounts of chlorine gas may form even when using an aluminium melt as the anode or part of the anode. This gas may be recovered.
An initiating chloride donor is provided to start the reactions in the salt melt. The initiating chloride donor may be aluminium chloride and/or at least one metal chloride that can be electrolyzed, i.e. so that chloride ions forms AICI3 at the contact surface between the salt melt and the aluminium melt.
In one embodiment, the initiating chloride donor includes a metal chloride of the same type as provided in the chloride salt composition, e.g. at least one metal chloride selected from the group consisting of chlorides of Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, and Ra.
In a preferred embodiment, the initiating chloride donor includes aluminium chloride added to the mixture before heating it or to the salt melt, said aluminium chloride being added up to 20 % by weight of the salt mixture, preferably 1-15 % by weight, more preferably 5-10% by weight. When using aluminium melt as the anode or part of the anode the steps dissolving and recovering by electrolysis are expedited simultaneously, preferably for at least 2 hours.
As the rare earth metal is deposited, additional REM containing resource can be stepwise or continuously added to the salt melt. The electrolysis and dissolving operation can for instance be performed for 2-8 hours; where after metals deposited at the cathode/s is collected, and the electrolysis can be restarted. To avoid interrupts of the electrolysis, another "clean" electrode can be submerged. Alternatively, the salt melt may have a plurality of electrodes which one after the other is activated as a cathode and while the former is deactivated. Thereby the metals can be selectively deposited at individual electrodes.
The voltage is suitably within the range of 2.5-5V, preferably 3-4 V. The rare earth metal may be co-deposited with aluminum or they may be selectively electrodeposited.
The residue after processing may contain A1203 and for instance other stable oxides such as Si02, depending on the contents of the REM containing resource; in particular if the REM containing resource contains REM oxides A1203 may form when chlorinating the REM oxides. The residues may for instance be used for landfill, building
construction or as a raw material for the refractory industry EXAMPLE
Neodymium refining from neodymium magnet was performed in a salt bath containing LiCl, KC1 and NaCl. Eutectic composition of the three salts was found from the ternary phase diagram and desired amounts of sodium chloride, lithium chloride and potassium chloride powders were mixed together carefully and the mixture was put in a dryer (T=l 10 °C) for 24 hours. The Neodymium magnet (Nd2Fel4B) was crushed and added together with aluminum chloride as fluxing agent to the mixture. The
Al CI 3 /neodymium ratio was 2/1 and the AlC13/salt ratio was 20 wt%. The whole mixture was weighted before each experiment. The masses of the each material are shown in the table 1.
Table 1 : amounts of different component used in the bath
Material A1C13 Nd2Fel4B NaCl KC1 LiCl
Amount [g] 3.69 7.5 1.87 7.8 8.81
The powders were poured in an alumina crucible and the crucible was put in the vertical furnace.
The time to reach the target temperature which was 850 °C was about 6 hours. Then the graphite electrodes were dipped into the salt bath and the electrolysis was started. The voltage was first set on 4 but due to the high current it was decreased to 3.2 in order to avoid constant current condition. The saturation current of the equipment which was used in this experiment was 5. By fixing the voltage on 4 the current increased to 4.99 (saturation current). Hence the voltage was decreased to 3.2 V. The electrolysis was done during 5 hours.
After the experiment, a thick deposited layer on cathode was observed. The deposited layer contained over 40 % by weight of Nd and over 20 % by weight of Al. The amount of Fe was below 5 % by weight. It should be noted that the essentially all Fe remained in the salt melt although the theoretical decomposition voltage of FeCl3 is below 1 V. From the experiment it can be concluded that Nd can be recovered from the salt melt by electrolysis.

Claims

process for recovering at least one rare earth metal (REM) from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, said process including the steps of: a) providing a crucible for supporting a salt melt; b) providing a salt melt consisting of (in weight %):
- 60-99 of a chloride salt composition consisting of at least two metal chlorides selected from the group consisting of chlorides of Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, and Ra;
- 1- 30 of A1C13 and,
optionally
- <10 of halides, additional chlorides, sulphides and/or oxides; c) providing at least one REM containing resource to the crucible before or after heating to form the salt melt, said REM containing resource including at least one rare earth metal from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; d) reacting the aluminium chloride as a chloride donor with at least one rare earth metal of the REM containing resource to form at least one rare earth metal chloride dissolved in the salt melt; e) maintaining the content of AICI3 in the salt melt by adding AICI3
stepwise or continuously as it is consumed or by in situ formation of AICI3 in the salt melt; f) recovering said at least one REM, preferably by electrolysing the salt melt and selectively electrodepositing at least one REM.
2. A process as claimed in claim 1, wherein the salt composition
comprises at least two of the salts selected from the group: NaCl, KC1, LiCl, and CaCl2, preferably at least three of the salts selected from the group: NaCl, KC1, LiCl, and CaCl2.
3. A process as claimed in claim 1, wherein the salt composition essentially consists of by weight % of the salt composition, 3-20 NaCl, 30-70 KC1, 20-60 LiCl, preferably 5-15 NaCl, 40-60 KC1, 30-50 LiCl, more preferably 7-12 NaCl, 45-55 KC1, 35-45 LiCl.
A process as claimed in claim 1, wherein the salt composition essentially consists of by weight % of the salt composition, 10-50 NaCl, 2-20 KC1, 50-80 CaCl2 preferably 25-35 NaCl, 3-10 KC1, 60-75 CaCl2.
A process as claimed in claim 1, wherein the salt composition essentially consists of by weight % of the salt composition, 5-20 NaCl, 20-40 LiCl, 40-70 CaCl2 preferably 7-15 NaCl, 25-35 LiCl, 50-60 CaCl2.
A process as claimed in claim 1, wherein the salt composition essentially consists of by weight % of the salt composition, 35-65 KC1, 20-50 LiCl, 5-20 CaCl2 preferably 45-55 KC1, 30-40 LiCl, 10-15 CaCl2.
A process as claimed in any one of claims 1-6, wherein the salt composition has a liquidus temperature below 700 °C preferably below 600 °C, more preferably below 500°C.
A process as claimed in any one of claims 1-7, wherein the process includes at least one of the following:
- providing the at least one REM containing resource into said liquid salt melt stepwise or continuously;
- maintaining the content of A1C13 within ±7%, preferably within ±5%.
A process as claimed in any one of claims 1-8, wherein the process includes at least one of the following:
- vaporizing metal chlorides from the melt and condensing them for subsequent recovery of the metals of the condensed chlorides;
- leaching metal chlorides from the melt in water and extracting the metals as hydroxides by a hydrometallurgical method;
- recycling the chloride salts of the melt;
- recovering a processing residue including A1203 and preferably using it for landfill, building construction, or as a raw material for refractory industry
- crushing and/or grinding and/or milling the REM containing resource before adding it to the crucible.
10. A process as claimed in any one of claims 1-9, wherein the at least one REM-resource is at least one of: - Permanent magnets, in particular Nd containing magnets, preferably NdFeB magnets;
- Batteries, preferably cathodes containing AB5, where A is lanthanum, cerium, neodymium and/or praseodymium, and B is nickel, cobalt, manganese and/or aluminium;
- Thin films
- lightnings and displays
-ores
- rare earth concentrates from ores.
11. A process as claimed in any one of claims 1-10, wherein the at least one
REM-resource includes at least one rare earth oxide from the group of: La203, Ce02, Pr6On, Nd203,Sm203, Eu203, Gd203, Tb407,
Dy203,Ho203, Er203, Tm203, Yb203, Lu203, and Y203.
12. A process as claimed in any one of claims 1-11, wherein providing at least one anode and at least one cathode to be in contact with the salt melt, and wherein recovering of the metals includes electrolyzing the salt melt to form at least one REM from the group Sc, Y, La, Ce, Pr Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu on the at least one cathode, preferably selectively electrodepositing at least one REM from the group Sc, Y, La, Ce, Pr Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
13. A process as claimed in any one of claims 12, wherein the method
includes at least one of the steps of:
- providing an aluminium melt at the bottom of the crucible, said aluminium melt forming the anode or a part of the anode, and
- providing an initiating chloride donor to the salt melt for starting the reactions in the salt melt, said initiating chloride donor being aluminium chloride and/or at least one metal chloride that can be electrolyzed, preferably the initial chloride donor is able to form aluminium chloride at the contact surface between the aluminium melt and the salt melt.
14. A process according to claim 13 wherein the initiating chloride donor is a metal chloride of the same type as provided in the chloride salt composition.
15. A process according to claim 13 wherein the initiating chloride donor includes aluminium chloride added to the mixture before heating it or to the salt melt, said aluminium chloride being added up to 20 % by weight of the chloride salt mixture, preferably 1-15 % by weight, more preferably 5-10% by weight.
16. A process as claimed in any one of claims 13-15, wherein the salt melt and the aluminium melt is held at a temperature above 660 °C, preferably between 700 °C and 1000 °C, more preferably below 900°C.
17. A process as claimed in any one of claims 13-16, wherein step d) and step f) are preformed simultaneously, preferably for at least 2 hours.
18. A process as claimed in any one of claims 13-17, wherein the process is partly or wholly self-supporting during steady state by the aluminum chloride formed during the electrolyzing.
19. A process as claimed in any one of claims 1-12, wherein the flux in the form of aluminium chloride is added to the mixture before heating it to a salt melt and/or to the salt melt, the aluminium chloride can be added in a single batch or in several batches as the aluminium chloride is consumed, preferably 5-30% by weight of the salt mixture when added in a single batch, more preferably 5-20 % by weight of the mixture, most preferably 7-15 wt%. 0 A process as claimed in claim 19 including at least one of the following - during step e) and g), holding the salt melt at a temperature of at least
500°C and at most 900 °C, preferably holding the salt melt at a temperature in the range of 550-700 °C, more preferably 580-650 °C;
- in step g), electrolyzing the melt for a time period on the order of 2 to 8 hours, preferably 3-6 hours;
- collecting chlorine gas evolved during the electrolysis;
- in step e), reacting the aluminium chloride for time period on the order of 2-10 hours , preferably 3-8 hours;
- controlling the weight ratio "flux'V'REM in the resource" is in the range of 0.1 - 3, preferably 0.2-2.0, more preferably 0.3-1.0, most preferably 0.4-0.6.
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