JP2015531827A - Recovery of rare earth metals - Google Patents

Abstract

The present invention provides 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 fed and REM containing resources are chlorinated using aluminum chloride. REM can be recovered by electrolysis, vaporization, or hydrometallurgy.

Description

TECHNICAL FIELD The present invention relates to 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, Lu. (REM).

Background Rare earth metals (ie Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) are increasingly important in today's society It has become. Thus, permanent magnets, in particular Nd-containing magnets such as NdFeB-magnets, AB5 (where A is lanthanum, cerium, neodymium and / or praseodymium and B is nickel, cobalt, manganese and / or aluminum. There is a growing demand to find improved methods for extracting rare earth metals from a variety of resources, including batteries such as battery cathodes, thin films, lighting and displays, ores, and rare earth concentrates from ores. ing.

The rare metal may exist in the form of a metal, but is generally an oxide such as La ₂ O ₃ , CeO ₂ , Pr ₆ O ₁₁ , Nd ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Gd _It can exist as ₂ O ₃ , Tb ₄ O ₇ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Tm ₂ O ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ , and Y ₂ O ₃ .

Objects of the invention The object of the present invention is to provide at least one from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. A method for recovering a rare earth metal from a resource containing at least one of these metals.

  Another object of the present invention is to recover Nd and / or Dy from Nd / Dy containing magnets.

DESCRIPTION OF THE INVENTION At least one of the aforementioned objects is at least from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu. Achieved by a process of recovering one rare earth metal (REM), which process
a) providing a crucible for holding a salt melt;
b) in weight percent units
-Chlorine consisting of at least two metal chlorides selected from the group consisting of Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, and Ra chlorides of 60-99. Salt composition,
Providing 1-30 AlCl ₃ , and optionally, a salt melt comprising 0-10 halides, additional chlorides, sulfides and / or oxides;
c) supplying at least one REM-containing resource to the crucible before or after heating to form a salt melt, wherein the REM-containing resource is Sc, Y, La, Ce, Pr, Nd, Including at least one rare earth metal from the group of Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu;
d) Aluminum chloride as chloride donor is reacted 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. Steps and;
In e) optionally, by the addition of AlCl ₃ stepwise or continuously or in situ formation of AlCl ₃ in a salt melt, (in situ formation) as is AlCl ₃ is consumed, AlCl ₃ levels Maintaining the steps;
f) recovering the at least one REM, preferably by electrolyzing the salt melt and selectively electrodepositing the 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 is recovered. be able to.

  The salt melt is preferably heated under a protective atmosphere, suitably under argon. The atmosphere may be nitrogen. Further, chlorine gas may be mixed in a nitrogen or argon atmosphere.

Salt composition For a given salt combination of a minimum of two chloride salts, the content of these salts is within 10% by weight, more preferably from the lowest eutectic point of the salt combination. It is preferably within 5% by weight, most preferably within 1% by weight. However, as long as the liquidus temperature of this salt combination is at least 50 ° C. below the operating temperature during electrolysis; preferably other contents may be used as long as it is 100 ° C. below the operating temperature. it can. Preferably, the salt composition is at least two of the salts selected from the group: NaCl, KCl, LiCl and CaCl ₂ , preferably the group: a salt selected from NaCl, KCl, LiCl and CaCl ₂ Including at least three of them.

  In a preferred embodiment, the at least one chloride salt composition is 3-20 NaCl, 30-70 KCl, 20-60 LiCl, preferably 5%, by weight percent of the at least one chloride salt. -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 comprises 10 to 50 NaCl, 2 to 20 KCl, 50 to 80 CaCl ₂ , preferably by weight percent of the at least one chloride salt. includes 25-35 of NaCl, 3 to 10 of KCl, the CaCl ₂ 60-75.

In an alternative embodiment, the at least one chloride salt composition comprises 5 to 20 NaCl, 20 to 40 LiCl, 40 to 70 CaCl ₂ , preferably by weight percent of the at least one chloride salt. comprises NaCl from 7 to 15, 25 to 35 of LiCl, the CaCl ₂ for 50-60.

In an alternative embodiment, the at least one chloride salt composition is 35 to 65 KCl, 20 to 50 LiCl, 5 to 20 CaCl ₂ , preferably 45 to 55, by weight percent of the salt composition. KCl, 30-40 LiCl, 10-15 CaCl ₂ .

Flux The flux is AlCl ₃ . The flux can be added before or after the salt melt is formed. Further, the flux may be added stepwise as the flux is consumed. In one embodiment, at least some to all of the AlCl ₃ is generated in situ by reacting chloride ions in the salt melt with the aluminum anode, preferably the aluminum anode is the aluminum melt at the bottom of the crucible. It is.

REM-containing resources The REM-containing resources may be crushed and / or ground and / or milled before being fed to the crucible. Prior to feeding the crucible, the crushed and / or ground and / or crushed may be pelletized.

The REM-containing resource can be, for example:
-Permanent magnets, in particular Nd and / or Dy containing magnets, preferably NdFeB magnets (Nd may be partially replaced by Dy). The magnet may be coated with metallic zinc, nickel, nickel + nickel, copper + nickel, nickel + copper + nickel, gold. These coatings can be selectively electrodeposited during electrolysis. The magnet may also include other metals such as Nb and Co. These metals can be selectively electrodeposited during electrolysis.
A battery, preferably a cathode containing AB5, where A is lanthanum, cerium, neodymium and / or praseodymium and B is nickel, cobalt, manganese and / or aluminum;
-Thin films;
-Lightnings and displays;
-Ore;
-Rare earth concentrates from ores;

Examples of the rare earth oxide include La ₂ O ₃ , CeO ₂ , Pr ₆ O ₁₁ , Nd ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₄ O ₇ , Dy ₂ O ₃ , Rare earth oxides from the group of Ho ₂ O ₃ , Er ₂ O ₃ , Tm ₂ O ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ and Y ₂ O ₃ are particularly suitable. Particularly targeted resources are those containing at least one of Dy, Nd, Pm, Sm, Ho, Er, Tm, Yb, and Lu. Currently, the elements of most interest for recovery are Dy and Nd. This is because these elements may exist in a high content in the permanent magnet.

  According to one preferred embodiment, submarine nodules are excluded as REM-containing resources. This is because the raw materials usually have a very low content of rare earth oxides and a large amount of base metals such as Mn, Fe and Ni.

The dissolution flux AlCl ₃ acts as a chloride donor that dissolves the rare earth metal oxide and / or rare earth metal into the rare earth metal chloride in the salt melt. The following chlorides can be formed depending on the earth oxide or metal present in the resource being 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 YCl _3.

If AlCl ₃ dissolves the rare earth metal oxide, aluminum will form Al ₂ O ₃ . When AlCl ₃ dissolves the rare earth metal, Al metal is released, which is very reactive and therefore probably reacts with other reducible chlorides in the salt melt.

  In one embodiment, the dissolving step d) is performed before the collecting step d). However, they may partially or fully overlap as described below in other embodiments, particularly in connection with the use of a liquid aluminum anode. In order to dissolve the REM-containing resource, the salt melt is maintained at an elevated temperature, usually between about 2 hours and about 10 hours, preferably 3-8 hours, more preferably 4-8 hours. The amount of the REM-containing resource is such that the weight ratio “flux” / “REM in resource” is between 0.1 and 3, preferably 0.2 to 2.0, more preferably 0.3 to 1.0, Most preferably, it is preferably 0.4 to 0.6. The temperature should be below 1000 ° C, more preferably below 900 ° C. For optimal economy, the temperature is preferably in the range of 550-700 ° C, more preferably 580-650 ° C during dissolution. In order to improve the 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 above the liquidus temperature of the salt melt. 100 ° C higher.

When dissolving a neodymium magnet (Nd ₂ Fe ₁₄ B), the reaction is Nd + AlCl ₃ = Al + NdCl ₃
Fe + AlCl ₃ = Al + FeCl ₃
B + AlCl ₃ = Al + BCl ₃
Can be.

The Gibbs energy for forming neodymium chloride is negative, while the Gibbs energy for forming FeCl ₃ and BCl ₃ is positive. Therefore, the formation of NdCl ₃ is more likely than the formation of FeCl ₃ and BCl ₃ . Neodymium can be recovered from neodymium chloride by electrolysis and / or vaporization.

Recovery Various processes can be used to recover REM resources from the melt. The salt melt used for extraction can optionally be recycled. Preferably, at least one rare earth metal and other metals can be selectively electrodeposited from the salt melt. However, it is also possible to use metal chloride vaporization and their condensation, or to leach the salt phase in water and extract the metal as a hydroxide by a hydrometallurgical process. This process can be designed to be continuous by combining the two steps. The treated residue, such as Al ₂ O ₃ , can be used for landfills, building structures, or as a raw material for the refractory industry. The salt can be recovered and reused.

  In a preferred embodiment, the REM is recovered by electrolysis by connecting at least one anode and at least one cathode to a salt melt. In this embodiment, the recovery includes 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 at least one It is selectively electrodeposited on the cathode.

  In one embodiment, the electrolysis is performed using conventional anode (s) and cathode (s), which is further described in “Electrolysis Using Conventional Anode and Cathode”. Explains.

  In the most preferred embodiment, the electrolysis includes an aluminum anode that promotes in situ formation of aluminum chloride. This is further described in “Dissolution and electrolysis using an aluminum anode”.

Electrolysis Using Conventional Anode and Cathode According to one embodiment, a conventional anode and cathode configuration is used, for example, at least one cathode and at least one anode submerged in a salt melt.

Preferably, two electrodes, for example graphite electrodes, are immersed in the melt and can be connected to a direct current power source. The theoretical decomposition voltage of MCl ₃ (where M is a rare earth metal) is about 2.5-3V. Preferably, a voltage in the range of 2.5-5V is used for electrolysis, more preferably 3-4V. If AlCl ₃ remains in the salt melt, AlCl ₃ may be selectively electrodeposited on the cathode or co-deposited with a rare earth metal.

The flux AlCl ₃ can be added in several batches or in a single batch as the aluminum chloride is consumed, and when added in a single batch, preferably 5-30% by weight of the salt mixture, more preferably It can be added at 5-20% by weight of the mixture, most preferably 7-15% by weight. Since it is difficult to recover the flux after the extraction process, it is desirable not to add excess aluminum chloride.

Therefore, it is preferable to carefully control the content of aluminum chloride in the salt melt. Furthermore, as detailed in “Dissolution”, it is preferred that there is a sufficient amount of AlCl ₃ in the melt in order to sufficiently form REM-chloride in the salt melt. Thus, in a preferred embodiment, the amount of AlCl ₃ is maintained at a sufficient level. This can be done by adding AlCl ₃ stepwise or continuously as AlCl ₃ is consumed and / or by allowing AlCl ₃ to form in situ in the salt melt. In situ formation of AlCl ₃ is described in “Dissolution and electrolysis using an aluminum anode”. The content of aluminum chloride in the salt melt depends on the material to be treated. In the neodymium magnet (Nd ₂ Fe ₁₄ B), the AlCl ₃ / Nd ratio is 2/1 considering the above-described reaction. In the example, 20% by weight AlCl ₃ was used. Preferably, the amount of AlCl ₃ is controlled within ± 7%, preferably within ± 5%, or within ± 3%.

  The electrolysis is preferably at least one rare earth from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. It is carried out in a crucible that holds the salt melt together with a dissolved REM-containing resource containing metal.

  During electrolysis, chloride ions are attracted to the anode. Using a conventional anode, such as a graphite electrode, generates chlorine gas from the salt melt and vaporizes it. Chlorine gas is preferably recovered.

  Preferably, the batch of melt is electrolyzed for 2-8 hours. During electrolysis, the temperature of the salt melt is preferably less than 1000 ° C, more preferably less than 900 ° C. For optimum economy, the temperature is preferably in the range of 550-700 ° C, more preferably 580-650 ° C. In order to improve the 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 above the liquidus temperature of the salt melt. 100 ° C higher.

  The dissolution step and the electrolysis step may be performed separately or may overlap completely or partially.

  At least the rare earth metals from the group Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and optionally other dissolved metals are The cathode can be selectively electrodeposited. After the deposition of one metal, the cathode can be removed and the metal deposited on the cathode can be extracted. To avoid interruption of electrolysis, another “clean” electrode can be submerged. Alternatively, the salt melt may have a plurality of electrodes, which in turn activate as the cathode and the previous electrode inactive. Thereby, metal can be selectively deposited on individual electrodes.

After recovering at least one rare earth metal and possibly other metals, the chloride salt of the salt melt can be recycled. The treated residue contains Al ₂ O ₃ and, depending on the content of the REM-containing resource, contains other stable oxides such as, for example, SiO ₂ . The residue can be used, for example, for landfills, building structures, or as raw materials for the refractory industry.

Melting and electrolysis using an aluminum anode In a preferred embodiment, at least one anode comprises aluminum, which is preferably in the form of an aluminum melt provided at the bottom of the crucible. For example, by immersing an electrode, such as a graphite electrode, in the aluminum melt and connecting the electrode positively during electrolysis, the aluminum melt forms the anode or part of the anode. Alternatively, the crucible is made at least in part with a conductive material that contacts the aluminum melt and the crucible is connected positively during electrolysis. Thereby, the crucible and the molten aluminum act as an anode. Of course, at least one cathode is also required during electrolysis, for example, one or more graphite electrodes are submerged in the salt melt.

  If the aluminum melt at the bottom of the crucible is used as an anode or part of an anode, the salt melt and aluminum are heated to a temperature at which both are in a liquid phase. In order to improve the 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 above the liquidus temperature of the salt melt. 100 ° C higher. The temperature should be at least 660 ° C. and 1000 ° C. or less, preferably the temperature is in the range of 700-900 ° C.

During electrolysis, metal from the metal chloride deposits on the cathode. At the contact surface between the salt melt and the aluminum melt, chloride ions react with the aluminum, thereby forming AlCl ₃ . This means that in steady state, the salt melt can be fully or partially self-supporting with respect to the flux AlCl _{3 and} the emission of chlorine gas is reduced. Even when an aluminum melt is used as the anode or part of the anode, a smaller amount of chlorine gas can be produced. This gas can be recovered.

An initiating chloride donor is fed to initiate the reaction in the salt melt. Initiating chlorides donors, aluminum chloride, and / or may be electrolyzed, i.e., chloride ions so as to form a AlCl ₃ at the contact surface between the salt melt and the aluminum melt, at least one Metal chloride may be used.

  In one embodiment, the starting chloride donor is the same type of metal chloride provided in the chloride salt composition, eg, Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr. And at least one metal chloride selected from the group consisting of chlorides of Ba and Ra.

  In a preferred embodiment, the starting chloride donor comprises aluminum chloride added to the mixture prior to its heating or added to the salt melt, the aluminum chloride being preferably up to 20% by weight of the salt mixture. Is added in an amount of 1 to 15 wt%, more preferably 5 to 10 wt%.

  If an aluminum melt is used as the anode or part of the anode, the melting step and the recovery step by electrolysis are preferably simultaneously accelerated for at least 2 hours.

  As the rare earth metal is deposited, additional REM-containing resources can be added to the salt melt stepwise or continuously. The electrolysis and dissolution operation can be performed, for example, for 2-8 hours; the metal deposited on the cathode can then be collected and the electrolysis can be resumed. Another “clean” electrode can be submerged to avoid interruption of electrolysis. Alternatively, the salt melt may have a plurality of electrodes, which in turn activate as the cathode and the previous electrode inactive. Thereby, metal can be selectively deposited on individual electrodes.

  The voltage is suitably in the range 2.5-5V, preferably 3-4V. The rare earth metal may be co-deposited with aluminum or may be selectively electrodeposited.

Residues after treatment may contain Al ₂ O ₃ and other stable oxides such as, for example, SiO ₂ depending on the content of the REM-containing resource; When REM oxide is contained, Al ₂ O ₃ may be generated when REM oxide is chlorinated. The residue can be used, for example, for landfills, building structures, or as raw materials for the refractory industry.

Example Neodymium refining from a neodymium magnet was performed in a salt bath containing LiCl, KCl, and NaCl. The eutectic composition of the three salts is found from the ternary phase diagram, the required amounts of sodium chloride, lithium chloride and potassium chloride powder are carefully mixed and the mixture is placed in a dryer (T = 110 ° C.) for 24 hours. It was. A neodymium magnet (Nd2Fe14B) was crushed and added to the mixture along with aluminum chloride as a fluxing agent. The AlCl ₃ / neodymium ratio was 2/1 and the AlCl ₃ / salt ratio was 20 wt%. The entire mixture was weighed before each experiment. Table 1 shows the mass of each material.

  The powder was poured into an alumina crucible, and the crucible was placed in a vertical furnace.

  The time to reach the target temperature of 850 ° C. was about 6 hours. Next, the graphite electrode (s) were immersed in a salt bath to initiate electrolysis. The voltage was initially set to 4, but due to the high current, the voltage was reduced to 3.2 to avoid a constant current condition. The saturation current of the device used in this experiment was 5. By fixing the voltage to 4, the current increased to 4.99 (saturation current). Therefore, the voltage was reduced to 3.2V. Electrolysis was performed for 5 hours.

After the experiment, a thickly deposited layer was observed on the cathode. The deposited layer contained more than 40 wt% Nd and more than 20 wt% Al. The amount of Fe was less than 5% by weight. It should be noted that the theoretical decomposition voltage of FeCl ₃ is less than 1 V, but essentially all Fe remained in the salt melt. From the experiments it can be concluded that Nd can be recovered from the salt melt by electrolysis.

Claims (20)

Method 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 Because
a) providing a crucible for holding the salt melt;
b) at least two metals selected from the group consisting of chlorides of Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba and Ra, in units of% by weight A chloride salt composition comprising chloride,
- 1~30 AlCl _3, as well as,
Optionally,
Providing a salt melt consisting of halides, additional chlorides, sulfides and / or oxides of ≦ 10;
c) supplying at least one REM-containing resource to a crucible before or after heating to form the salt melt, wherein the REM-containing resource is Sc, Y, La, Ce, Pr, Including at least one rare earth metal from the group of Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu;
d) reacting aluminum 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 AlCl _{3 in} the salt melt by adding AlCl ₃ stepwise or continuously as AlCl ₃ is consumed or by in situ formation of AlCl _{3 in} the salt melt Step to do;
f) recovering the at least one REM, preferably by electrolyzing the salt melt and selectively electrodepositing the at least one REM. Salt composition, NaCl, KCl, at least two of the salts selected from the group of LiCl and CaCl _2, preferably at least three of salt selected NaCl, KCl, from the group of LiCl and CaCl ₂ The method of claim 1 comprising a species.   The salt composition is essentially 3-20 NaCl, 30-70 KCl, 20-60 LiCl, preferably 5-15 NaCl, 40-60 KCl, 30% by weight of the salt composition. The method of claim 1, comprising ˜50 LiCl, more preferably 7-12 NaCl, 45-55 KCl, 35-45 LiCl. The salt composition is essentially 10 to 50 NaCl, 2 to 20 KCl, 50 to 80 CaCl ₂ , preferably 25 to 35 NaCl, 3 to 10 KCl, by weight percent of the salt composition. The method according to claim 1, comprising 60 to 75 CaCl ₂ . Salt composition consists essentially, in weight percent of the salt composition, 5 to 20 NaCl, 20 to 40 of LiCl, CaCl ₂ 40 to 70, preferably NaCl of 7-15, 25-35 of LiCl, The method according to claim 1, comprising 50-60 CaCl ₂ . The salt composition is essentially 35 to 65 KCl, 20 to 50 LiCl, 5 to 20 CaCl ₂ , preferably 45 to 55 KCl, 30 to 40 LiCl, by weight percent of the salt composition. The method according to claim 1, comprising 10 to 15 CaCl ₂ .   The process according to any one of claims 1 to 6, wherein the salt composition has a liquidus temperature of less than 700 ° C, preferably less than 600 ° C, more preferably less than 500 ° C. following:
-Supplying at least one REM-containing resource stepwise or continuously into said liquid salt melt;
The method according to any one of claims 1 to 7, comprising at least one step of maintaining the content of AlCl ₃ within ± 7%, preferably within ± 5%. following:
-Vaporizing the metal chloride from the melt and condensing the metal chloride for later recovery of the condensed chloride metal;
-Leaching the metal chloride from the melt into water and extracting the metal as a hydroxide by hydrometallurgy;
-Recycling the molten chloride salt;
- Al treated residue was collected containing ₂ O _3, preferably, landfill, used as a raw material for the or refractory industry for building construction step;
The method according to any one of the preceding claims, comprising at least one step of crushing and / or grinding and / or crushing the REM-containing resource before adding the REM-containing resource to the crucible. At least one REM resource is:
-Permanent magnets, in particular Nd-containing magnets, preferably NdFeB magnets;
- battery, preferably, AB ₅ (In the formula, A, lanthanum, cerium, neodymium and / or praseodymium, B is nickel, cobalt, manganese and / or aluminum) containing cathode;
The method according to claim 1, wherein the method is at least one of a rare earth concentrate from the ore. At least one REM resource is La ₂ O ₃ , CeO ₂ , Pr ₆ O ₁₁ , Nd ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₄ O ₇ , Dy ₂ O _3. 11. The composition of claim 1, comprising at least one rare earth oxide from the group of: Ho ₂ O ₃ , Er ₂ O ₃ , Tm ₂ O ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ and Y ₂ O ₃ . The method according to any one of the above.   At least one anode and at least one cathode are placed in contact with the salt melt, and a metal recovery step electrolyzes the salt melt to produce Sc, Y, La, Ce, Pr, Nd , Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and at least one REM is formed on at least one cathode, preferably Sc, Y, Selectively electrodepositing at least one REM from the group of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, 12. A method according to any one of the preceding claims. -Providing an aluminum melt to the bottom of the crucible, said aluminum melt forming an anode or part of the anode; and-starting chloride to initiate the reaction in the salt melt Supplying a starting donor to the salt melt, wherein the starting chloride donor is aluminum chloride and / or at least one metal chloride that can be electrolyzed, preferably the starting chloride donor 13. The method of claim 12, comprising at least one of the steps of being capable of forming aluminum chloride at the interface between the aluminum melt and the salt melt.   14. The method of claim 13, wherein the starting chloride donor is the same type of metal chloride as provided in the chloride salt composition.   The starting chloride donor comprises aluminum chloride added to the mixture before its heating or added to the salt melt, said aluminum chloride being up to 20% by weight of the chloride salt mixture, preferably 1-15. 14. A process according to claim 13 added in wt%, more preferably 5-10 wt%.   16. The salt melt and the aluminum melt are maintained at a temperature above 660 ° C, preferably between 700 ° C and 1000 ° C, more preferably below 900 ° C. Method.   17. A method according to any one of claims 13 to 16, wherein step d) and step f) are performed simultaneously, preferably for at least 2 hours.   18. A method according to any one of claims 13 to 17, wherein the method is partially or fully self-supporting during steady state by aluminum chloride formed during electrolysis.   A flux in the form of aluminum chloride is added to the mixture before heating to its salt melt and / or is added to the salt melt so that the aluminum chloride is consumed in several batches as the aluminum chloride is consumed. Or can be added in a single batch, 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% by weight The method according to any one of claims 1 to 12. During the following steps e) and g), the salt melt is kept at a temperature of at least 500 ° C. and at most 900 ° C., preferably the salt melt is 550-700 ° C., more preferably 580-650 ° C. Holding at a temperature in the range;
In step g) electrolyzing the melt for a period of about 2 to 8 hours, preferably about 3 to 6 hours;
-Collecting chlorine gas released during electrolysis;
In step e) reacting aluminum chloride for a period of the order of 2 to 10 hours, preferably 3 to 8 hours;
-The weight ratio "flux" / "REM in resource" is 0.1-3, preferably 0.2-2.0, more preferably 0.3-1.0, most preferably 0.4-0. 20. The method of claim 19, comprising at least one of the steps of controlling to a range of .6.