Electrochemical system for metal recovery

Abstract

Metal recovery apparatus ( 20 ) being a diaphragm-less electrolytic cell arrangement where oxidizing reactions are achieved in a cathode cell ( 32 ) in an anode mode and reducing reactions in the anode cell ( 43 ) in a cathode mode by changing the direction of current flow. Better performance is achieved by pulsing ( 27 b ) the DC power ( 27 b ) to the electrodes and in some applications, installing plastic mesh ( 165 ) over the surface of the solution electrodes ( 24, 31 ) to reduce unwanted side reaction.

1 . An electrochemical apparatus comprising a first cell and a second cell, the first cell including a first main electrode and a first solution electrode and the second cell including an second main electrode and a second solution electrode, a power supply to supply DC power to the first and second cells, an electrical connection between the main electrode of one of the cells with the solution electrode of the other of the cells via the power supply and a direct electrical connection between the main electrode of the other of the cells with the solution electrode of the other of the cells, an electrolyte supply to the first cell, an enriched electrolyte transfer line between the first cell and the second cell and a depleted electrolyte line from the second cell, whereby metal is taken into solution from a metal source in the first cell and is deposited in the second cell. 
     
     
         2 . An electrochemical apparatus as in  claim 1  wherein the first cell is an anode cell and the second cell is a cathode cell. 
     
     
         3 . An electrochemical apparatus as in  claim 1  wherein the first cell is a cathode cell and the second cell is an anode cell. 
     
     
         4 . An electrochemical apparatus as in  claim 1  wherein the first cell comprises a first cell assembly of an anode cell and a cathode cell and the second cell comprises a second cell assembly of an anode cell and a cathode cell. 
     
     
         5 . An electrochemical apparatus as in  claim 1  further including a frequency modulator associated with the DC power source whereby to supply a pulsed DC power to the first and second cells. 
     
     
         6 . An electrochemical apparatus as in  claim 6  wherein the frequency modulator has a frequency range of from 10 to 100 kilohertz. 
     
     
         7 . An electrochemical apparatus as in  claim 6  wherein the frequency modulator has a duty cycle of the pulsing DC power of from 10 to 90 percent. 
     
     
         8 . An electrochemical apparatus as in  claim 1  wherein the first main electrode and the second main electrode are made of expanded titanium sheet coated with platinum group oxides. 
     
     
         9 . An electrochemical apparatus as in  claim 1  wherein the first main electrode and the second main electrode are made from expanded metal sheets selected from aluminum, iron, copper or stainless steel. 
     
     
         10 . An electrochemical apparatus as in  claim 1  wherein the first main electrode comprises an expanded metal sheet and is sandwiched between two first solution electrodes and the second main electrode comprises an expanded metal sheet and is sandwiched between two second solution electrodes and non-conductor baffles are installed between the respective main electrodes and the solution electrodes whereby to force electrolyte flowing through the respective cells to weave in and out of the expanded metal electrodes. 
     
     
         11 . An electrochemical apparatus as in  claim 1  further including a plastic mesh covering the surface of each of the solution electrodes whereby to trap a layer of electrolyte thereagainst. 
     
     
         12 . An electrochemical apparatus comprising a first electrochemical cell assembly and a second electrochemical cell assembly,
 the first electrochemical cell assembly including comprising a first anode cell and a second anode cell, the first anode cell including a first main electrode and a first solution electrode, the second anode cell including a second main electrode and a second solution electrode, a first power supply to supply DC power to the first and second anode cells, an electrical connection between the first main electrode of the first anode cell with the second solution electrode of the second anode cell via the first power supply and a direct electrical connection between the second main electrode of the second anode cell with the first solution electrode of the first anode cell,   the second electrochemical cell assembly including comprising a first cathode cell and a second cathode cell, the first cathode cell including a third main electrode and a third solution electrode, the second cathode cell including a fourth main electrode and a fourth solution electrode, a second power supply to supply DC power to the first and second cathode cells, an electrical connection between the third main electrode of the first cathode cell with the fourth solution electrode of the second cathode cell via the second power supply and a direct electrical connection between the fourth main electrode of the second cathode cell with the third solution electrode of the first cathode cell,   an electrolyte supply to the first anode cell, a first electrolyte transfer line between the first anode cell and the second anode cell, an enriched electrolyte transfer line between the second anode cell and the first cathode cell, a second electrolyte transfer line between the first cathode cell and the second cathode cell and a depleted electrolyte line from the second cell, whereby metal is taken into solution from a metal source in the first cell and is deposited in the second cell.   
     
     
         13 . An electrochemical apparatus as in  claim 12  wherein each of the first power supply and the second power supply comprise a frequency modulator associated with the DC power source whereby to supply a pulsed DC power to the first and second cell assemblies. 
     
     
         14 . An electrochemical apparatus as in  claim 14  wherein each of the frequency modulators have a duty cycle of the pulsing DC power of from 10 to 90 percent. 
     
     
         15 . An electrochemical apparatus as in  claim 14  wherein each of the frequency modulators have a frequency range of from 10 to 100 kilohertz. 
     
     
         16 . An electrochemical apparatus as in  claim 12  wherein each of the main electrodes are made of expanded titanium sheet coated with platinum group oxides. 
     
     
         17 . An electrochemical apparatus as in  claim 12  wherein each of the main electrodes are made from expanded metal sheets selected from aluminum, iron, copper or stainless steel. 
     
     
         18 . An electrochemical apparatus as in  claim 1  wherein the each of the main electrode comprises an expanded metal sheet and is sandwiched between respective solution electrodes and non-conductor baffles are installed between the respective main electrodes and the solution electrodes whereby to force electrolyte flowing through the respective cells to weave in and out of the expanded metal electrodes. 
     
     
         19 . An electrochemical apparatus as in  claim 12  further including a plastic mesh covering the surface of each of the solution electrodes whereby to trap a layer of electrolyte thereagainst.