Separation of metals

Abstract

The invention provides a process for the separation of metals, the metals being comprised as the metal oxides in a mixed oxide sample, the process comprising: (i) adding the mixed oxide to a molten salt electrolyte and cathodically electrolysing the oxide, the potential of the cathode being controlled so as to favour oxygen ionisation over deposition of metal from the cations present in the molten salt, and the applied potential difference being such as to facilitate selective reduction of one metal oxide at the expense of other metal oxides; and (ii) separating the metal from the remaining metal oxides, wherein the metal oxides comprise oxides of metals from at least one of the transition metal, lanthanide or actinide series The process is applicable to mixed oxide samples comprising mixtures of two or more metal oxides, and a particular application is in the separation of zirconium and hafnium comprised in mixed zirconium and hafnium oxides, the removal of hafnium facilitating the use of the zirconium in fuel cladding for use in the nuclear power industry.

1 . A process for the separation of metals, said metals comprising metal oxides in a mixed oxide sample, the process comprising: 
 (i) adding the mixed oxide to a molten salt electrolyte and cathodically electrolysing the oxide, the potential of the cathode being controlled so as to favour oxygen ionisation over deposition of metal from the cations present in the molten salt, and the applied potential difference being such as to facilitate selective reduction of one metal oxide at the expense of other metal oxides; and    (ii) separating the metal from the remaining metal oxides    wherein said metal oxides comprise oxides of metals from at least one of the transition metal, lanthanide or actinide series.    
   
   
       2 . The process of  claim 1  wherein said mixed oxide sample comprises a mixture of two or more metal oxides.  
   
   
       3 . The process of  claim 1  wherein said metals comprise zirconium and hafnium and said mixed oxide sample comprises mixed zirconium and hafnium oxides.  
   
   
       4 . The process of  claim 1  wherein the mixed oxide is provided as solid pieces of irregular size and shape, a powder, an amorphous mass, or a dense solid agglomerate.  
   
   
       5 . The process of  claim 1  wherein the oxide is located in a mesh basket which forms the cathode.  
   
   
       6 . The process of  claim 1  whrein the molten salt electrolyte comprises at least one chloride salt.  
   
   
       7 . The process of  claim 6  wherein the cloride salt is CaCl 2  or BaCl 2 .  
   
   
       8 . The process of  claim 1  wherein the anode is a carbon anode.  
   
   
       9 . The process of  claim 1  wherein the step of separating the metal from the remaining metal oxides is carried out by the use of dissolution and solvent extraction techniques, heating and slagging methods or electrochemical means.  
   
   
       10 . The process of  claim 1  wherein said reduction of the selected metal oxide is carred out in one molten salt whilst separation of the metal from the other metal oxide or oxides is effected in a different molten salt composition.  
   
   
       11 . The process of  claim 1  wherein said reduction of the selected metal oxide and said separation of the metal from the other metal oxide or oxides is performed in the same molten salt.