Selective reductive electrowinning apparatus and method

Abstract

A method and electrochemical cell for recovery of metals is provided, where the electrochemical cell includes an anode disposed in an anodic chamber, a cathode disposed in a cathodic chamber, an ion-conducting separator disposed between the anode and the cathode to physically separate the anodic and cathodic chambers, a basic pH anolyte containing a sacrificial reductant disposed within the anodic chamber, an acidic pH catholyte containing metal ions disposed within the cathodic chamber, and an electrical connection between the anode and the cathode. The method includes applying a voltage or an electrical current to an electrolytic cell across the cathode and the anode and is sufficient to reduce the metal ions to form an elemental metal species at the cathode, and to oxidize the sacrificial reductant at the anode.

What is claimed is: 
     
         1 . A method of recovering metals comprising:
 applying a voltage or an electrical current to an electrolytic cell comprising:
 an anode disposed in an anodic chamber; 
 a cathode disposed in a cathodic chamber; 
 a separator disposed between the anode and the cathode to physically separate the anodic and cathodic chambers, the separator allowing the transport of ions between the anodic and cathodic chambers; 
 an anolyte disposed within the anodic chamber, comprising a sacrificial reductant, wherein the anolyte has a basic pH; 
 a catholyte disposed within the cathodic chamber, comprising at least one or more metallic ions dissolved therein, wherein the catholyte has an acidic pH; and 
 an electrical connection between the anode and the cathode, wherein the voltage or the electrical current is applied to the electrolytic cell across the cathode and the anode via the electrical connection, wherein the voltage or the electrical current is sufficient to reduce the at least one or more metallic ions to form at least one or more elemental metal species at the cathode, and to oxidize the sacrificial reductant at the anode. 
   
     
     
         2 . The method of  claim 1 , wherein the voltage or electrical current is less than a value necessary to affect a substantial generation of hydrogen at the cathode and/or a substantial generation of oxygen at the anode. 
     
     
         3 . The method of  claim 1 , wherein the sacrificial reductant is selected from the group consisting of urea, ammonia, ethanol, methanol, and a combination thereof. 
     
     
         4 . The method of  claim 1 , wherein the separator comprises a cation conducting polymer comprising:
 a polymeric backbone comprising polyetheretherketones, polyetherketones, polyethersulfones, polyphenylene sulfide, polyphenylene ethers, polyparaphenylene, polyethylene, polypropylene, polystyrene, a fluoropolymer, or combinations thereof; and   a plurality of protonic acid groups covalently bonded to the polymeric backbone.   
     
     
         5 . The method of  claim 1 , wherein the anode or the cathode comprise a material independently selected from the group consisting of cobalt, copper, iron, nickel, platinum, iridium, ruthenium, rhodium, and mixtures thereof and alloys thereof. 
     
     
         6 . The method of  claim 1 , wherein the anode further comprises a support material at least partially layered with one or more metals, metal mixtures, or alloys. 
     
     
         7 . The method of  claim 1 , wherein the anolyte comprises an alkaline electrolyte composition. 
     
     
         8 . The method of  claim 7 , wherein the alkaline electrolyte composition comprises an hydroxide salt selected from the group consisting of lithium hydroxide, rubidium hydroxide, cesium hydroxide, barium hydroxide, strontium hydroxide, potassium hydroxide, sodium hydroxide, magnesium hydroxide, calcium hydroxide, potassium carbonate, sodium carbonate, and mixtures thereof. 
     
     
         9 . The method of  claim 7 , wherein the alkaline electrolyte composition comprises a polymeric gel. 
     
     
         10 . The method of  claim 9 , wherein the polymeric gel comprises polyacrylic acid, polyacrylates, polymethacrylates, polyacrylamides, sulfonated-polymers or combinations thereof. 
     
     
         11 . The method of  claim 1 , wherein the at least one or more metallic ions is a cation of a metal selected from the group consisting of zinc, chromium, tantalum, gallium, iron, cadmium, indium, thallium, cobalt, nickel, tin, lead, copper, bismuth, silver, mercury, gold, chromium, niobium, vanadium, manganese, aluminum, and combinations thereof. 
     
     
         12 . The method of  claim 1 , wherein the anolyte has a pH of about 8 or greater. 
     
     
         13 . The method of  claim 1 , wherein the electrolytic cell operates at a temperature in a range from about 0° C. to about 80° C. 
     
     
         14 . The method of  claim 1 , wherein the anodic chamber further comprises a first inlet and a first outlet, the method further comprising:
 flowing the anolyte into the anodic chamber through the first inlet;   oxidizing at least a portion of the sacrificial reductant in the anolyte to form a modified anolyte;   discharging the modified anolyte from the anodic chamber through the first outlet; and   optionally, recirculating the modified anolyte through the anodic chamber.   
     
     
         15 . The method of  claim 1 , wherein the cathodic chamber further comprises a second inlet and a second outlet, the method further comprising:
 flowing the catholyte into the cathodic chamber through the second inlet;   reducing at least a portion of the at least one or more metallic ions to form at least one or more elemental metal species to form a modified catholyte;   discharging the modified catholyte from the cathodic chamber through the second outlet; and   optionally, recirculating the modified catholyte through the cathodic chamber.   
     
     
         16 . An electrochemical cell comprising:
 an anode in an anodic chamber;   a cathode in a cathodic chamber;   a separator disposed between the anode and the cathode to physically separate the anodic and cathodic chambers, the separator allowing the transport of ions between the anodic and cathodic chambers;   an anolyte disposed within the anodic chamber, comprising a sacrificial reductant, wherein the anolyte has a basic pH;   a catholyte disposed within the cathodic chamber, comprising one or more metallic ions dissolved therein, wherein the catholyte has an acidic pH; and   an electrical connection between the anode and the cathode.   
     
     
         17 . The electrochemical cell of  claim 16 , wherein the separator comprises a cation conducting polymer comprising:
 a polymeric backbone comprising polyetheretherketones, polyetherketones, polyethersulfones, polyphenylene sulfide, polyphenylene ethers, polyparaphenylene, polyethylene, polypropylene, polystyrene, a fluoropolymer, or combinations thereof; and   a plurality of protonic acid groups covalently bonded to the polymeric backbone.   
     
     
         18 . The electrochemical cell of  claim 17 , wherein the protonic acid groups is selected from the group consisting of sulfonic acids, carbonic acids, phosphoric acids, or boronic acids. 
     
     
         19 . The electrochemical cell of  claim 17 , wherein the cation conducting polymer comprises a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer; a sulfonated poly(ether ether ketone); or a sulfonated polyimide. 
     
     
         20 . The electrochemical cell of  claim 19 , wherein the sulfonated tetrafluoroethylene-based fluoropolymer-copolymer is ethanesulfonyl fluoride, 2-[1-[difluoro-[(trifluoroethenyl)oxy]methyl]-1,2,2,2-tetrafluoroethoxy]-1,1,2,2,-tetrafluoro-, with tetrafluoroethylene.