Method of determining the extent of a metal oxide reduction

Abstract

The present invention relates to a method for determining the extent of electrochemical extraction of a metal (M) from a metal (M) oxide caused by a voltage applied between a cathode comprising (or consisting essentially of) or in contact with the metal (M) oxide and an inert metal alloy anodein an oxygen-dissolving molten electrolyte.

1 . A method for determining the extent of electrochemical extraction of a metal (M) from a metal (M) oxide caused by a voltage applied between a cathode comprising or in contact with the metal (M) oxide and an inert metal alloy anode in an oxygen-dissolving molten electrolyte, the method comprising:
 (a) measuring the current flow between the cathode and the inert metal alloy anode over a temporal range;   (b) relating a characteristic of the current flow between the cathode and the inert metal alloy anode over the temporal range to the extent of electrochemical extraction of the metal (M) from the metal (M) oxide.   
     
     
         2 . A method as claimed in  claim 1  wherein the current flow between the cathode and the inert metal alloy anode over the temporal range includes a point of inflection. 
     
     
         3 . A method, as claimed in  claim 1  wherein in step (b), the characteristic of the current flow between the cathode and the inert metal alloy anode over the temporal range is a quantitative characteristic. 
     
     
         4 . A method as claimed in  claim 3  wherein the quantitative characteristic is beyond a point of inflection of the current flow over the temporal range. 
     
     
         5 . A method as claimed in  claim 3  wherein the quantitative characteristic of the current flow beyond a point of inflection of the current flow over the temporal range is the measured current and step (b) is:
 relating the measured current to the rate of extraction of the metal (M) from the metal (M) oxide. 
 
     
     
         6 . A method as claimed in  claim 4  wherein the quantitative characteristic is a threshold current beyond a point of inflection of the current flow over the temporal range. 
     
     
         7 . A method as claimed in  claim 1  wherein step (b) comprises: relating the characteristic of the current flow between the cathode and the inert metal alloy anode over the temporal range to an extent of extraction beyond which is the onset of the formation of undesirable by-products or the onset of corrosive conditions. 
     
     
         8 . A method as claimed in  claim 1  wherein step (b) comprises: relating the characteristic of the current flow between the cathode and the inert metal alloy anode over the temporal range to a target rate of extraction (%) of metal (M) from metal (M) oxide or a target oxygen content of metal (M). 
     
     
         9 . A method as claimed in  claim 1  wherein the temporal range is less than 8 hours. 
     
     
         10 . A method as claimed in  claim 1  wherein the electrochemical extraction is carried out in the presence of an alkali metal (M a ) oxide. 
     
     
         11 . A method as claimed in  claim 1  wherein the metal (NI) is one or more metals selected from the group consisting of Ti, Nb, Ta, U, Th, Cr, Fe, steel and Zr. 
     
     
         12 . A method as claimed in  claim 1  wherein the metal (M) is Ti. 
     
     
         13 . A method as claimed in  claim 1  wherein the metal (M) oxide optionally in admixture with an alkali metal (M a ) oxide or an alkali metal (M a ) salt decomposable into the alkali metal (M a ) oxide is the cathode. 
     
     
         14 . A method as claimed in  claim 1  wherein the molten electrolyte contains CaCl 2 . 
     
     
         15 . A method as claimed in  claim 1  wherein the anode is composed of an Al-E-Cu based alloy comprising an intermetallic phase of formula:
 wherein:
 E denotes one or more metallic elements; 
 x is an integer in the range 1 to 5; 
 y is an integer being 1 or 2; and 
 z is an integer being 1 or 2. 
 
 
     
     
         16 . A method as claimed in  claim 15  wherein E is one or more metallic elements selected from the group consisting of Ru, Zr, Cr, Nb, V, Co, Ta, Fe, Ni, La and Mn. 
     
     
         17 . A method as claimed in  claim 1  wherein the metal (A) oxide is TiO 2 , the molten electrolyte contains CaCl 2  and the electrochemical extraction is carried out in the presence of an alkali metal (M a ) oxide. 
     
     
         18 . The method of  claim 1  wherein the cathode consists essentially of a metal (M) oxide or is in contact with the metal (M) oxide.