Method and system for recovering rare earth elements from within an object
Disclosed is a method and system for recovering at least rare earth elements from within an object A consisting of at least one first rare earth portion or a mixture of rare earth elements and a second metal portion. The method includes a solvothermal treatment step that places the object in contact with a fluid for causing at least one rare earth portion and/or mixture of rare earth elements and the metal portion to oxidize in order to separate same, the value of the reaction temperature Tr is selected according to the nature of the object, the reaction following a R-M→R(X)x+M(X)y scheme, where R is the rare earth element or a mixture of rare earth elements, M is the transition metal, and (X) is a group which depends on the fluid used.
1. Method for recovering at least rare earth elements contained in an object A composed of a first rare earth portion or mixture of rare earth elements and of a second metal portion serving as a protective antioxidant layer, the method comprising a solvothermal treatment step performed in the presence of at least one solvent, the solvent being water or water and organic solvent, the solvent optionally comprising catalysts, to place the object “A” in contact with a fluid or mixture of fluids adapted to cause the separation of the rare earth and the metal portions, then the oxidation of at least one rare earth portion and/or mixture of rare earth elements, the fluid or mixture of fluids comprising one or more components having a molar mass higher than 2 g.mol −1 , the value of the reaction temperature Tr, wherein Tr is a temperature of the solvothermal treatment, being chosen according to the type of object A, with a maximum value lower than the melting point of the object A and a minimum value higher than the evaporation temperature of the solvent, the reaction following a scheme R-M→R(OH)x+M(O)y where R is the rare earth element or mixture of rare earth elements, and M is a transition metal.
2. The method according to claim 1 , wherein the object “A” is a magnetic component composed of at least one rare earth element and a magnetic alloy, the fluid being a solvent adapted to separate the rare earth elements from the protective antioxidant layer formed by the metal portion coating the magnet, the rare earth elements then being separated by oxidation.
3. The method according to claim 1 , wherein the reaction temperature Tr is chosen to be at least equal to the initiation temperature of an oxidation process of the constituent elements of the object A, and which allows diffusion of the oxidant within the object A.
4. The method according to claim 1 , wherein the fluid is placed under supercritical conditions.
5. The method according to claim 1 , wherein the object “A” comprising a Nd 2 Fe 14 B magnetic phase, an oxidizing solvent is used as fluid, the magnetic phase is dissociated leading to the separation of neodymium and the other elements in the form of crystals, in accordance with the process Nd 2 Fe 14 B→Nd(OH) 3 +Fe 3 O 4 .
6. The method according to claim 5 , wherein the oxidizing solvent comprises salt sodium chloride and/or sulfur oxides, and is conducted at a temperature higher than 100° C.
7. The method according to claim 1 , wherein the object A is an electrode in a rare earth/metal alloy used in a primary or secondary battery.
8. The method according to claim 1 , wherein the treatment time of the solvothermal treatment is chosen as a function of subsequent treatment of the elements and/or crystals formed at the end of the method.
9. The method according to claim 1 , further comprising a pre-treatment step of the object A via grinding and/or demagnetization.
10. System for recovering rare earths contained in an object A composed of at least one first rare earth portion or mixture of rare earth elements and of a second metal portion, the system comprising at least the following parts:
an enclosure ( 1 ) receiving object A and a fluid having characteristics adapted to cause oxidation of at least the first rare earth portion and/or of the second metal portion; and
means ( 10 ) for raising the temperature of said enclosure ( 1 ), the value of the reaction temperature Tr being chosen to trigger the reaction for implementation of the method according to claim 1 .
11. The method of claim 5 , wherein the oxidizing solvent is water.
12. The method according to claim 11 , wherein the oxidizing solvent comprises salt sodium chloride and/or sulfur oxides, and is conducted at a temperature higher than 100° C.