Chemically facilitated electrochemical methods for recovery of rare earth elements

Abstract

A method for recovery of rare earth elements includes forming a rare earth containing ionic solution comprising an ionic liquid and a solvent having one or more rare earth elements dissolved therein. The method also includes adding a polar protic solvent to the rare earth containing ionic solution, and applying an electrical potential across the rare earth containing ionic solution. The method further includes collecting a deposit of at least one rare earth element on at least one electrode disposed in the rare earth containing ionic solution, and recovering the deposit of at least one rare earth element from the at least one electrode. Additional methods for recovery of rare earth elements are disclosed.

What is claimed is: 
     
         1 . A method for recovery of rare earth elements comprising:
 forming a rare earth containing ionic solution comprising an ionic liquid and a solvent having one or more rare earth elements dissolved therein;   adding a polar protic solvent to the rare earth containing ionic solution;   applying an electrical potential across the rare earth containing ionic solution;   collecting a deposit of at least one rare earth element on at least one electrode disposed in the rare earth containing ionic solution; and   recovering the deposit of the at least one rare earth element from the at least one electrode.   
     
     
         2 . The method of  claim 1 , wherein adding the polar protic solvent to the rare earth containing ionic solution comprises creating a metal species coordination environment therein. 
     
     
         3 . The method of  claim 2 , wherein adding the polar protic solvent to the rare earth containing ionic solution comprises creating a metal species coordination environment therein which facilitates reduction of the one or more of rare earth metal complexes via a single step reduction pathway. 
     
     
         4 . The method of  claim 2 , wherein creating the metal species coordination environment in the rare earth containing ionic solution comprises facilitating partitioning of rare earth metal complexes in the rare earth containing ionic solution. 
     
     
         5 . The method of  claim 4 , wherein creating the metal species coordination environment comprises facilitating reduction of the rare earth metal complexes via a single step reduction pathway. 
     
     
         6 . The method of  claim 1 , wherein adding the polar protic solvent to the rare earth containing ionic solution comprises adding the polar protic solvent to the rare earth containing ionic solution at a concentration ratio of about 1:2 polar protic solvent:rare earth elements. 
     
     
         7 . The method of  claim 1 , wherein adding the polar protic solvent to the rare earth containing ionic solution comprises adding water to the rare earth containing ionic solution. 
     
     
         8 . The method of  claim 6 , wherein adding the polar protic solvent to the rare earth containing ionic solution comprises adding water to the rare earth containing ionic solution. 
     
     
         9 . The method of  claim 1 , wherein forming the rare earth containing ionic solution comprising the ionic liquid and the solvent having one or more rare earth elements dissolved therein comprises forming the rare earth containing ionic solution having from about 10 mM to about 500 mM of the rare earth elements. 
     
     
         10 . The method of  claim 1 , wherein forming the rare earth containing ionic solution comprising the ionic liquid and the solvent having one or more rare earth elements dissolved therein comprises forming the rare earth containing ionic solution comprising the ionic liquid having the following chemical formula: 
       
         
           
           
               
               
           
         
         wherein, R1 is selected from the group of a pyrrolidinium ion (C 4 H 10 N + ), an N-pyrrolidinium ion, an N-phenyl ion, and an N-N phenyl ion; R2 is selected from the group of cyanide, carboxyl, hydrogen, a hydrocarbon group containing at least 1 carbon atom and up to 12 carbon atoms, a difluoromethanesulfonamide ion, a perfluorobutanesulfonic acid ion, and, an n-methylsulfonyl ion; and, R3 is selected from the group of cyanide, carboxyl, hydrogen, and a hydrocarbon group containing at least 1 carbon atom and up to 12 carbon atoms, and an n-methylsulfonyl ion. 
       
     
     
         11 . The method of  claim 1 , wherein forming the rare earth containing ionic solution comprising the ionic liquid and the solvent having one or more rare earth elements dissolved therein comprises forming the rare earth containing ionic solution comprising the ionic liquid including one or more of 1-butyl-1-methylpyrrolidinium triflate (BMPyOTf), 1-butyl-1-methylpyrrolidinium bistriflimide (BMPyNTf 2 ), bistriflimide pyrrolidinium, imidazolium, piperidinium, 6, 6, 7, 7, 8, 8, 8-heptafluoro-2, 2-dimethyl-3, 5-octanedione, hexafluoroacetylacetone, 1, 1, 5, 5, 6, 6, 6-octafluoro-2, 4-hexanedione, 1, 1, 1-trifluoro-2, 4-pentanedione, 1, 1, 1-trifluoro-5, 5-dimethyl-2, 4-hexanedione, 4, 4, 4-trifluoro-1-phenyl-1, 3-butanedione, or a phosphonium-based ionic liquid. 
     
     
         12 . The method of  claim 1 , wherein forming the rare earth containing ionic solution comprising the ionic liquid and the solvent having one or more rare earth elements dissolved therein comprises forming the rare earth containing ionic solution comprising one or more of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium. 
     
     
         13 . The method of  claim 1 , wherein applying the electrical potential across the rare earth containing ionic solution comprises applying the electrical potential of from about +1.0V to about −4.0V across the rare earth containing ionic solution. 
     
     
         14 . The method of  claim 1 , wherein applying the electrical potential across the rare earth containing ionic solution comprises applying the electrical potential across the rare earth containing ionic solution containing at a temperature of from about 20° Celsius to about 25° Celsius. 
     
     
         15 . The method of  claim 1 , wherein applying the electrical potential across the rare earth containing ionic solution comprises applying the electrical potential across the rare earth containing ionic solution in an inert atmosphere. 
     
     
         16 . A method for recovery of rare earth elements comprising:
 dissolving one or more rare earth elements from one or more rare earth containing components into a solvent;   combining an ionic liquid with the solvent containing the one or more rare earth elements to form a rare earth containing ionic solution;   adding a polar protic solvent to the rare earth containing ionic solution;   applying an electrical potential across at least two electrodes operatively positioned in the rare earth containing ionic solution;   collecting a deposit of at least one rare earth element on at least one of the at least two electrodes; and   recovering the deposit of the at least one rare earth element from the at least one of the least two electrodes.   
     
     
         17 . The method of  claim 16 , wherein adding a polar protic solvent to the rare earth containing ionic solution comprises combining from about 0.5 percent to about 30 percent by volume of the solvent containing the one or more of rare earth relative to the volume of the ionic liquid. 
     
     
         18 . The method of  claim 16 , wherein dissolving one or more rare earth elements from one or more rare earth containing components into a solvent comprises dissolving the one or more rare earth elements into the solvent comprising propylene carbonate, dimethyl formamide, dimethyl sulfoxide (DMSO), trimethyl phosphate, a sulfonate, acetonitrile, acetic acid, ammonia, bistriflimide acid, or combinations thereof. 
     
     
         19 . The method of  claim 16 , wherein applying the electrical potential across the at least two electrodes operatively positioned in the rare earth containing ionic solution comprises forming a current density of from about 0.5 mA/cm 2  to about 5 mA/cm 2  at the at least two electrodes. 
     
     
         20 . A method for recovery of rare earth elements from rare earth containing materials comprising:
 separating rare earth containing components from a rare earth containing material;   drying the rare earth containing components to reduce a water content therein to below about 5 percent by weight;   dissolving the dried rare earth containing components in a solvent to a rare earth element concentration of from about 10 mM to about 500 mM in the solvent;   combining an ionic liquid with the solvent containing the rare earth elements to form a rare earth containing ionic solution, the solvent comprising from about 0.5 percent to about 30percent of a total amount of the ionic liquid by volume;   adding a polar protic solvent to the rare earth containing ionic solution, wherein the polar protic solvent is added to a concentration of about 50 percent of the concentration of the rare earth elements in the rare earth containing ionic solution;   applying an electrical potential of from about +1.0V to about −4.0V across at least one anode and at least one cathode operatively positioned in the rare earth containing ionic solution in an electrochemical cell;   collecting a deposit of at least one rare earth element on the at least the one cathode; and   recovering the deposit of the at least one rare earth element from the at least one cathode.