Electrorecovery of gold and silver from leaching solutions by simultaneous cathodic and anodic deposits

Abstract

This relates to mining and mineral or materials treatment industries that deal with gold and silver. Specifically, it is related to the process to recover gold and silver from thiosulfate or thiourea solutions, with an electrolysis that occurs simultaneously on both the anode and cathode. Increased velocity and greatly reduced energy consumption are obtained in relation to those found in conventional electrolytic cells.

1 . (canceled) 
     
     
         2 . A method for recovering silver or gold from a mineral comprising performing electrolysis from a thiosulfate or thiourea leaching solution simultaneously depositing the silver or gold on anode and cathode surfaces by operating in potential zones that permit silver or gold reduction at the cathode and ligand oxidation at the anode. 
     
     
         3 . The method according to  claim 2 , further comprising combining the leaching solution with the mineral in a leaching stage and circulating the leaching solution to an electrochemical reactor including the cathode and the anode. 
     
     
         4 . The method according to  claim 3 , further comprising recirculating the leaching solution to the leaching stage after the silver or gold is deposited on the anode and cathode surfaces. 
     
     
         5 . The method according to  claim 3 , further comprising filtering the leaching solution after the leaching stage, and prior to electrolysis. 
     
     
         6 . The method according to  claim 2 , further comprising abrading the cathode and anode mechanically to remove the silver or gold metals. 
     
     
         7 . The method according to  claim 2 , wherein the anode comprises copper and the cathode comprises titanium. 
     
     
         8 . The method according to  claim 2 , wherein the potential zone comprises a cell voltage of 100 mV, wherein the potential at the cathode is −260 mV versus a normal hydrogen electrode. 
     
     
         9 . A method for recovering a metal from a flotation concentrate comprising:
 (a) transferring a leaching solution to the flotation concentrate in a leaching stage to generate a metal-leaching solution;   (b) filtering the metal-leaching solution;   (c) circulating the filtered metal-leaching solution to an electrochemical reactor comprising an electrochemical cell having an anode and a cathode; and   (d) performing electrolysis on the metal-leaching solution, the electrolysis resulting in a deposition of the metal onto the anode and cathode.   
     
     
         10 . The method according to  claim 9 , wherein the metal is gold or silver and the leaching solution comprises thiosulfate or thiourea. 
     
     
         11 . The method according to  claim 10 , wherein the metal is silver and the leaching solution comprises 0.2 M (NH 4 ) 2 S 2 O 3 , 0.05 M CuSO 4 , 0.025 M EDTA, and 0.1 M (NH 4 ) 2 HPO 4 . 
     
     
         12 . The method according to  claim 9 , wherein the anode comprises a copper plate with a 60 cm 2  exposed geometrical area and the cathode comprises a titanium plate with a 60 cm 2  exposed geometrical area. 
     
     
         13 . The method according to  claim 9 , wherein the flotation concentrate has a particle size of less than 10 μm. 
     
     
         14 . The method according to  claim 9 , wherein electrolysis comprises a cell voltage of 100 mV, wherein the potential at the cathode is −260 mV versus a normal hydrogen electrode. 
     
     
         15 . The method according to  claim 9 , wherein the leaching stage comprises at least 2 hours of continuous agitation. 
     
     
         16 . The method according to  claim 9 , further comprising collecting the metal deposited on the anode and cathode by abrading the anode and cathode. 
     
     
         17 . The method according to  claim 9 , further comprising recirculating the leaching solution to a subsequent leaching stage after performing electrolysis. 
     
     
         18 . A method for recovering silver from a flotation concentrate comprising silver, comprising:
 (a) transferring a leaching solution to the flotation concentrate in a leaching stage to generate a silver-leaching solution;   (b) filtering the silver-leaching solution;   (c) circulating the filtered silver-leaching solution to an electrochemical reactor comprising an electrochemical cell having a copper anode and a titanium cathode;   (d) performing electrolysis on the metal-leaching solution, the electrolysis resulting in a deposition of the metal onto the anode and cathode;   (e) recovering the silver from the electrochemical reactor by mechanically abrading the anode and cathode, wherein leaching solution remains in the reactor;   (f) recirculating the leaching solution to the leaching stage; and   (g) repeating steps (a) through (f) a plurality of times.   
     
     
         19 . The method according to  claim 18 , wherein electrolysis comprises a cell voltage of 100 mV, wherein the potential at the cathode is −260 mV versus a normal hydrogen electrode. 
     
     
         20 . The method according to  claim 19 , wherein the electrolysis further comprises a current of 0.01 A, which together with the cell voltage translates to 0.004 W-h. 
     
     
         21 . The method according to  claim 20 , wherein the leaching solution comprises 0.2 M (NH 4 ) 2 S 2 O 3 , 0.05 M CuSO 4 , 0.025 M EDTA, and 0.1 M (NH 4 ) 2 HPO 4 .