Electrochemical cell for recovery of metals from solid metal oxides

Abstract

An electrochemical cell and methods of using the electrochemical cell are described that can be utilized for the recovery of metals from metal oxides. The cell includes a first electrode that includes a solid metal oxide, an electrolyte including an oxygen ion conductor, and a second electrode space apart from the electrolyte by an oxygen ion conducting membrane. Upon reduction of the metal oxide, solid metal is formed that replaces the metal oxide of the electrode and provides for simplified recovery of the metal from the metal oxide. The membrane protects the second electrode from corrosion and degradation from the electrolyte, increasing the life of the cell.

What is claimed is: 
     
         1 . An electrochemical cell comprising:
 a first electrode including a solid metal oxide and a first current collector;   a second electrode including a material that encourages the oxidation of oxygen ion and a second current collector, the first and second electrodes being in electrical communication with one another;   an electrolyte comprising an alkali metal or alkaline earth metal salt or a eutectic or mixture thereof;   an oxygen ion conducting compound mixed with the electrolyte;   an oxygen ion conducting membrane separating the electrolyte from the second electrode.   
     
     
         2 . The electrochemical cell of  claim 1 , the solid metal oxide including uranium oxide. 
     
     
         3 . The electrochemical cell of  claim 1 , the solid metal oxide including an oxide of a noble metal. 
     
     
         4 . The electrochemical cell of  claim 1 , wherein the metal oxide is chopped, ground, porous. 
     
     
         5 . The electrochemical cell of  claim 1 , wherein the metal oxide is held in a container. 
     
     
         6 . The electrochemical cell of  claim 1 , wherein the electrolyte includes a chloride salt of sodium, potassium, lithium, magnesium, calcium, aluminum, or a fluoride salt of sodium, potassium, lithium, magnesium, calcium, aluminum, or cryolite or a mixture or eutectic thereof. 
     
     
         7 . The electrochemical cell of  claim 1 , wherein the oxygen ion conducting compound comprises an alkali metal oxide or alkali earth metal oxide. 
     
     
         8 . The electrochemical cell of  claim 1 , wherein the oxygen ion conducting compound comprises lithium oxide. 
     
     
         9 . The electrochemical cell of  claim 1 , wherein the oxygen ion conducting compound comprises a metal oxide that is the same as the solid metal oxide of the first electrode. 
     
     
         10 . The electrochemical cell of  claim 1 , wherein the oxygen ion conducting membrane comprises a solid composition including one or more oxides containing divalent and/or trivalent cations and one or more oxides containing tetravalent cations. 
     
     
         11 . The electrochemical cell of  claim 10 , wherein the oxygen ion conducting membrane comprises zirconia or hafnia stabilized in cubic form by one or more of MgO, NiO, SrO, CaO, NiO, Y 2 O 3 , Sc 2 O 3 , La 2 O 3 , Gd 2 O 3  and Ce 2 O 3 . 
     
     
         12 . The electrochemical cell of  claim 1 , wherein the oxygen ion conducting membrane is immersed in the electrolyte. 
     
     
         13 . The electrochemical cell of  claim 1 , wherein the oxygen ion conducting membrane is a container and contains the electrolyte in the interior of the container, 
     
     
         14 . The electrochemical cell of  claim 1 , wherein the material that encourages the oxidation of oxygen ion comprises platinum, a noble metal, a silver alloy, a cermet, an electronic oxide, a composite thereof stabilized with zirconia, or a carbonaceous substance. 
     
     
         15 . The electrochemical cell of  claim 14 , wherein the material that encourages the oxidation of oxygen ion comprises platinum. 
     
     
         16 . The electrochemical cell of  claim 1 , wherein the second electrode is porous. 
     
     
         17 . The electrochemical cell of  claim 1 , wherein the second electrode is a layer on the oxygen ion conducting membrane. 
     
     
         18 . A method for recovering a metal from a metal oxide comprising:
 locating a first electrode in an electrochemical cell, the electrochemical cell comprising the first electrode including a solid metal oxide and a first current collector, a second electrode including a material that encourages the oxidation of oxygen ion and a second current collector, an electrolyte comprising an alkali metal or alkaline earth metal salt or a eutectic or mixture thereof, an oxygen ion conducting compound mixed with the electrolyte, and an oxygen ion conducting membrane separating the electrolyte from the second electrode;   applying a voltage potential across the first and second electrodes, wherein the voltage potential is greater than the dissociation potential of the metal oxide of the first electrode, the voltage potential driving a reaction of the metal oxide to form oxygen ions and a solid metal in the place of the solid metal oxide of the first electrode, the oxygen ions being conducted across the electrolyte via the oxygen ion conducting compound and across the oxygen ion conducting membrane to the second electrode, the oxygen ions being oxidized to form a molecular oxygen species at the second electrode.   
     
     
         19 . The method of  claim 18 , wherein the solid metal oxide comprises uranium oxide. 
     
     
         20 . The method of  claim 19 , wherein the uranium oxide is a component of spent nuclear fuel. 
     
     
         21 . The method of  claim 18 , wherein the reaction of the metal oxide includes the formation of a Magneli phase in the metal oxide. 
     
     
         22 . The method of  claim 18 , further comprising following formation of the solid metal in the place of the solid metal oxide removal of the first electrode from the electrochemical cell. 
     
     
         23 . The method of  claim 22 , further comprising locating a third electrode in the electrochemical cell in place of the first electrode, the third electrode comprising a solid metal oxide and a current collector, and thereafter applying the voltage potential across the third electrode and the second electrode, 
     
     
         24 . The method of  claim 18 , further comprising preprocessing the metal oxide prior to locating the first electrode in the electrochemical cell,