Method and apparatus for electrowinning copper using the ferrous/ferric anode reaction and a flow-through anode

Abstract

The present invention relates, generally, to a method and apparatus for electrowinning metals, and more particularly to a method and apparatus for copper electrowinning using the ferrous/ferric anode reaction and a flow-through anode, such as, for example, a dimensionally stable carbon, carbon composite, metal-graphite, or stainless steel anode. In general, the use of a flow-through anode—coupled with an effective electrolyte circulation system—enables the efficient and cost-effective operation of a copper electrowinning system employing the ferrous/ferric anode reaction at a total cell voltage of less than about 1.5 V and at current densities of greater than about 26 Amps per square foot (about 280 A/m2), and reduces acid mist generation. Furthermore, the use of such a system permits the use of low ferrous iron concentrations and optimized electrolyte flow rates as compared to prior art systems while producing high quality, commercially saleable product (i.e., LME Grade A copper cathode or equivalent), which is advantageous.

1 . A method of electrowinning copper comprising: 
 providing an electrochemical cell comprising at least one flow-through anode and at least one cathode, wherein said cathode has an active surface area;    providing a flow of electrolyte through said electrochemical cell, said electrolyte comprising copper and solubilized ferrous iron;    oxidizing at least a portion of said solubilized ferrous iron in said electrolyte at the at least one flow-through anode from ferrous iron to ferric iron;    removing at least a portion of said copper from said electrolyte at the at least one cathode; and    operating said electrochemical cell at a cell voltage and at a current density, wherein said cell voltage is less than about 1.5 Volts and wherein said current density is greater than about 26 amperes per square foot of active cathode.    
     
     
         2 . The method according to  claim 1 , wherein said step of oxidizing comprises oxidizing at least a portion of said solubilized ferrous iron in said electrolyte at an anode comprising at least one of a metal mesh, a porous metal structure, a wool or fabric, a plurality of metal strips, a plurality of metal wires, a woven wire cloth, a plurality of metal rods, a perforated metal sheet, or a combination thereof.  
     
     
         3 . The method according to  claim 2 , wherein said step of oxidizing comprises oxidizing at least a portion of said solubilized ferrous iron in said electrolyte at an anode comprising at least one of titanium, tantalum, zirconium, niobium, nickel, a stainless steel, a metal alloy, an intermetallic mixture, or a ceramic or cermet containing one or more metals.  
     
     
         4 . The method according to  claim 1 , wherein said step of oxidizing comprises oxidizing at least a portion of said solubilized ferrous iron in said electrolyte at an anode having an electrochemically active coating.  
     
     
         5 . The method according to  claim 4 , wherein said step of oxidizing comprises oxidizing at least a portion of said solubilized ferrous iron in said electrolyte at an anode having an electrochemically active coating comprising at least one of: platinum; ruthenium; iridium; a Group VIII metal; a Group VIII metal oxide; a compound comprising a Group VIII metal; an oxide of titanium, molybdenum, tantalum, or a mixture thereof; or a compound comprising titanium, molybdenum, tantalum, or a mixture thereof.  
     
     
         6 . The method according to  claim 1 , said step of oxidizing comprises oxidizing at least a portion of said solubilized ferrous iron in said electrolyte at an anode comprising at least one of carbon, graphite, or a mixture of carbon and graphite.  
     
     
         7 . The method according to  claim 6 , wherein said step of oxidizing comprises oxidizing at least a portion of said solubilized ferrous iron in said electrolyte at an anode comprising at least one of a carbon foam, a graphite foam, a metal-graphite sintered material, a polycrystalline graphite, a polycrystalline graphite coated or densified with a graphitizable pitch material, a graphite foam coated or densified with graphitizable pitch material, a fiber reinforced carbon-carbon composite, a fiber reinforced carbon-carbon composite incorporating graphitizable particulates, a graphite coated metal mesh, or a carbon coated metal mesh.  
     
     
         8 . The method according to  claim 1 , wherein said step of oxidizing comprises oxidizing at least a portion of said solubilized ferrous iron in said electrolyte at an anode having a coating comprising at least one of carbon, graphite, a mixture of carbon and graphite, a precious metal oxide, or a spinel.  
     
     
         9 . The method according to  claim 1 , said step of oxidizing comprises oxidizing at least a portion of said solubilized ferrous iron in said electrolyte at an anode comprising stainless steel-clad copper rods.  
     
     
         10 . The method according to  claim 1 , said step of oxidizing comprises oxidizing at least a portion of said solubilized ferrous iron in said electrolyte at an anode comprising a titanium mesh having a coating comprising a mixture of carbon black powder and graphite powder in a graphitizable pitch binder.  
     
     
         11 . A system for electrowinning copper from a copper-containing electrolyte, comprising: 
 an electrolyte stream, wherein said electrolyte stream comprises copper and solubilized ferrous iron, and wherein the concentration of solubilized ferrous iron in said electrolyte stream is from about  10  to about 60 grams per liter;    an electrochemical cell, wherein said electrochemical cell comprises at least one flow-through anode, at least one cathode, and an electrolyte flow manifold.    
     
     
         12 . The system according to  claim 11 , wherein said at least one flow-through anode comprises at least one of a metal mesh, a porous metal structure, a wool or fabric, a plurality of metal strips, a plurality of metal wires, a woven wire cloth, a plurality of metal rods, a perforated metal sheet, or a combination thereof.  
     
     
         13 . The system according to  claim 11 , wherein said at least one flow-through anode comprises at least one of titanium, tantalum, zirconium, niobium, nickel, a stainless steel, a metal alloy, an intermetallic mixture, or a ceramic or cermet containing one or more metals.  
     
     
         14 . The system according to  claim 11 , wherein said at least one flow-through anode comprises an electrochemically active coating.  
     
     
         15 . The system according to  claim 14 , wherein said at least one flow-through anode comprises an electrochemically active coating comprising at least one of: platinum; ruthenium; iridium; a Group VIII metal; a Group VIII metal oxide; a compound comprising a Group VIII metal; an oxide of titanium, molybdenum, tantalum, or a mixture thereof; or a compound comprising titanium, molybdenum, tantalum, or a mixture thereof.  
     
     
         16 . The system according to  claim 11 , wherein said at least one flow-through anode comprises at least one of carbon, graphite, or a mixture of carbon and graphite.  
     
     
         17 . The system according to  claim 16 , wherein said at least one flow-through anode comprises at least one of a carbon foam, a graphite foam, a metal-graphite sintered material, a polycrystalline graphite, a polycrystalline graphite coated or densified with a graphitizable pitch material, a graphite foam coated or densified with graphitizable pitch material, a fiber reinforced carbon-carbon composite, a fiber reinforced carbon-carbon composite incorporating graphitizable particulates, a graphite coated metal mesh, or a carbon coated metal mesh.  
     
     
         18 . The system according to  claim 11 , wherein said at least one flow-through anode comprises at least one of carbon, graphite, a mixture of carbon and graphite, a precious metal oxide, or a spinel.  
     
     
         19 . The system according to  claim 11 , wherein said at least one flow-through anode comprises stainless steel-clad copper rods.  
     
     
         20 . The system according to  claim 11 , wherein said at least one flow-through anode comprises a titanium mesh having a coating comprising a mixture of carbon black powder and graphite powder in a graphitizable pitch binder.