Methods for electrometallizating rare earth elements using anhydrous electrolytes comprising one or more silylamide compounds

Abstract

A method for electrometallizing one or more rare earth elements includes combining a rare earth element-containing compound comprising one or more rare earth elements with a silylamide-containing anhydrous electrolyte comprising one or more silylamide compounds to form a complex-containing anhydrous electrolyte comprising one or more silylamide-rare earth element complexes. The method also includes applying an electrical potential across electrodes of an electrochemical cell containing the complex-containing anhydrous electrolyte. The electrodes are disposed in the complex-containing anhydrous electrolyte. The method further includes collecting a deposit of at least one rare earth element on at least one electrode. Also disclosed is a system for electrometallizing one or more rare earth elements.

What is claimed is: 
     
         1 . A method for electrometallizing one or more rare earth elements, comprising:
 combining a rare earth element-containing compound comprising one or more rare earth elements with a silylamide-containing anhydrous electrolyte comprising one or more silylamide compounds to form a complex-containing anhydrous electrolyte comprising one or more silylamide-rare earth element complexes;   applying an electrical potential across electrodes of an electrochemical cell containing the complex-containing anhydrous electrolyte, the electrodes disposed in the complex-containing anhydrous electrolyte; and   collecting a deposit of at least one rare earth element on at least one electrode.   
     
     
         2 . The method of  claim 1 , wherein the one or more silylamide compounds has the following chemical formula: 
       
         
           
           
               
               
           
         
         wherein: 
         A comprises at least one of lithium, sodium, potassium, or calcium; 
         R 1 , R 2 , R 3 , R 4 , R 5 , and R 6  each independently comprises hydrogen, an alkyl group, or a combination thereof; and 
         X is 1 or 2. 
       
     
     
         3 . The method of  claim 2 , wherein A comprises lithium, calcium, or a combination thereof. 
     
     
         4 . The method of  claim 2 , wherein R 1 , R 2 , R 3 , R 4 , R 5 , and R 6  are a methyl group. 
     
     
         5 . The method of  claim 2 , wherein at least one of R 1 , R 2 , R 3 , R 4 , R 5 , and R 6  is an alkyl group comprising from one carbon atom to six carbon atoms. 
     
     
         6 . The method of  claim 1 , wherein the one or more silylamide compounds comprise lithium bis(trimethylsilyl)amide, sodium bis(trimethylsilyl)amide, potassium bis(trimethylsilyl)amide, calcium bis(trimethylsilyl)amide, or a combination thereof. 
     
     
         7 . The method of  claim 1 , wherein the rare earth element comprises lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, yttrium, or a combination thereof. 
     
     
         8 . The method of  claim 1 , wherein applying the electrical potential across the electrodes of the electrochemical cell comprises applying the electrical potential at a temperature of from about 20° C. to about 25° C. 
     
     
         9 . The method of  claim 1 , wherein applying the electrical potential across the electrodes of the electrochemical cell comprises applying the electrical potential across at least two electrodes maintained under an inert atmosphere. 
     
     
         10 . The method of  claim 1 , wherein applying an electrical potential across electrodes of an electrochemical cell comprises reducing the one or more silylamide-rare earth element complexes to deposit the one or more rare earth elements on the at least one electrode. 
     
     
         11 . A method for electrometallizing at least one rare earth element, comprising:
 combining a rare earth element-containing compound comprising at least one rare earth element with a silylamide-containing anhydrous electrolyte comprising at least one silylamide compound to form a complex-containing anhydrous electrolyte comprising at least one silylamide-rare earth element complex;   providing an electrochemical cell comprising the complex-containing anhydrous electrolyte, at least one cathode disposed in the complex-containing anhydrous electrolyte, and at least one anode disposed in the complex-containing anhydrous electrolyte;   applying an electrical potential across the at least one cathode and the at least one anode of the electrochemical cell;   collecting a deposit comprising the at least one rare earth element on the at least one cathode of the electrochemical cell; and   recovering the at least one rare earth element from the collected deposit,   wherein the at least one silylamide compound has the following chemical formula:   
       
         
           
           
               
               
           
         
         
           wherein: 
           A comprises at least one of lithium, sodium, potassium, or calcium; 
           R 1 , R 2 , R 3 , R 4 , R 5 , and R 6  each independently comprises hydrogen, a C1-C6 alkyl group, or a combination thereof; and 
           X is 1 or 2. 
         
       
     
     
         12 . The method of  claim 11 , wherein the rare earth element-containing compound comprises a rare earth salt, a rare earth oxide, a rare earth nitrate, a rare earth chloride, a rare earth trifluoromethanesulfanone, a rare earth carbonate, a rare earth bistriflimide, or a combination thereof. 
     
     
         13 . The method of  claim 11 , wherein the rare earth element comprises neodymium, dysprosium, or a combination thereof. 
     
     
         14 . The method of  claim 11 , wherein the at least one silylamide compound comprises lithium bis(trimethylsilyl)amide, calcium bis(trimethylsilyl)amide, or a combination thereof. 
     
     
         15 . The method of  claim 11 , wherein the at least one silylamide compound is substantially free of one or more of fluorine, oxygen, sulfur, or boron atoms. 
     
     
         16 . A system for electrometallizing one or more rare earth elements, the system comprising:
 a container configured to contain a complex-containing anhydrous electrolyte therein, the complex-containing anhydrous electrolyte comprising at least one silylamide-rare earth element complex;   an electrodeposition reservoir configured to receive an amount of the complex-containing anhydrous electrolyte from the container, the electrodeposition reservoir including:
 a reservoir inlet configured to facilitate an addition of the complex-containing anhydrous electrolyte into the electrodeposition reservoir; and 
 a reservoir outlet configured to facilitate a removal of a spent complex-containing anhydrous electrolyte from the electrodeposition reservoir, the spent complex-containing anhydrous electrolyte exhibiting a lower amount of the at least one silylamide-rare earth element complex compared to the complex-containing anhydrous electrolyte; 
   at least one counter-electrode and at least one working electrode disposed below a surface of the complex-containing anhydrous electrolyte in the electrodeposition reservoir,
 the at least one counter-electrode configured to release electrons to the complex-containing anhydrous electrolyte upon an application of an electrical potential across the at least one counter-electrode and at least one working electrode, and 
 the at least one working electrode configured to receive a deposit of the at least one rare earth element from a reduction of the complex-containing anhydrous electrolyte upon the application of the electrical potential across the at least one counter-electrode and the at least one working electrode; and 
   a potential source configurated to apply the electrical potential across the at least one counter-electrode and the at least one working electrode.   
     
     
         17 . The system of  claim 16 , wherein the system is configured to operate in a batch mode, a semi-batch mode, or a continuous mode. 
     
     
         18 . The system of  claim 16 , wherein the potential source is configured to apply the electrical potential of from about +1.0V to about −4.0V across the at least one counter-electrode and at least one working electrode. 
     
     
         19 . The system of  claim 16 , wherein the potential source is configured to generate a current density of from about 0.5 mA/cm 2  to about 5 mA/cm 2  between the at least one counter-electrode and the at least one working electrode, and through the complex-containing anhydrous electrolyte. 
     
     
         20 . The system of  claim 16 , further comprising a controlled environment enclosure dimensioned and configured to contain the electrodeposition reservoir, the at least one counter-electrode, the at least one working electrode, and the potential source therein,
 the controlled environment enclosure including at least one evacuation outlet configured to facilitate a removal of an ambient atmosphere within the controlled environment enclosure, and at least one inert gas inlet configured to receive the inert gas into the controlled environment enclosure.