Recovery of rare earth metals

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.

1 . 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, 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 AlCl 3  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 AlCl 3  in the salt melt by adding AlCl 3  stepwise or continuously as it is consumed or by in situ formation of AlCl 3  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, KCl, LiCl, and CaCl 2 , preferably at least three of the salts selected from the group: NaCl, KCl, LiCl, and CaCl 2 . 
     
     
         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 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. 
     
     
         4 . 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 KCl, 50-80 CaCl 2  preferably 25-35 NaCl, 3-10 KCl, 60-75 CaCl 2 . 
     
     
         5 . 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 CaCl 2  preferably 7-15 NaCl, 25-35 LiCl, 50-60 CaCl 2 . 
     
     
         6 . A process as claimed in  claim 1 , wherein the salt composition essentially consists of by weight % of the salt composition, 35-65 KCl, 20-50 LiCl, 5-20 CaCl 2  preferably 45-55 KCl, 30-40 LiCl, 10-15 CaCl 2 . 
     
     
         7 . A process as claimed in  claim 1 , wherein the salt composition has a liquidus temperature below 700° C. preferably below 600° C., more preferably below 500° C. 
     
     
         8 . A process as claimed in  claim 1 , 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 AlCl 3  within ±7%, preferably within ±5%.   
     
     
         9 . A process as claimed in  claim 1 , 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 Al 2 O 3  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  claim 1 , 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 AB 5 , 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  claim 1 , wherein the at least one REM-resource includes at least one rare earth oxide from the group of: 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 ,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 . 
     
     
         12 . A process as claimed in  claim 1 , 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  claim 1 , 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  claim 13 , 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  claim 13 , wherein step d) and step f) are preformed simultaneously, preferably for at least 2 hours. 
     
     
         18 . A process as claimed in  claim 13 , 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  claim 1 , 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 %. 
     
     
         20 . 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”/“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.