Treatment of reclaim water for use in metals recovery

Abstract

A process for improving the recovery of gold from gold-bearing solutions formed from carbonaceous ore using a cyanide lixiviant, the process comprising treatment of tailings pond water with H 2 SO 5 before introduction into a gold-recovery system such that the water has a total concentration of CN − and SCN − reduced by at least 30%.

1 . A process for recovering gold from carbonaceous ore in a cyanide-based gold recovery operation, the process comprising: 
 removing tailings from the cyanide-based gold-recovery operation, the tailings comprising CN −  and SCN − ;    holding the tailings in a reservoir;    removing an initial water effluent comprising an initial total concentration of CN −  and SCN −  from the reservoir;    treating the initial water effluent to oxidize CN −  and SCN −  to yield a treated water effluent having a treated total concentration of CN −  and SCN −  which is at least 30% below said initial total concentration of CN −  and SCN −  in the initial water effluent; and    introducing said treated water effluent into a gold-recovery operation to recover gold from carbonaceous ore with preg robbing tendencies.    
   
   
       2 . The process of  claim 1  wherein the treated total concentration of CN −  and SCN −  is below about 10 ppm.  
   
   
       3 . The process of  claim 1  wherein the treated total concentration of CN −  and SCN −  is below about 5 ppm.  
   
   
       4 . The process of  claim 1  wherein the treated water effluent has no detectable treated total concentration of CN −  and SCN − .  
   
   
       5 . The process of  claim 1  wherein said treating the initial water effluent to oxidize CN −  and SCN −  comprises treating the initial water effluent with H 2 SO 5 .  
   
   
       6 . The process of  claim 5  wherein the initial water effluent is treated with at least about 100% of the stoichiometric requirement of H 2 SO 5  necessary to react with the total initial concentration of CN −  and SCN − .  
   
   
       7 . The process of  claim 5  wherein the initial water effluent is treated with at least about 125% of the stoichiometric requirement of H 2 SO 5  necessary to react with the total initial concentration of CN −  and SCN − .  
   
   
       8 . The process of  claim 5  wherein the initial water effluent is treated with at least about 150% of the stoichiometric requirement of H 2 SO 5  to react with the total initial concentration of CN −  and SCN − .  
   
   
       9 . The process of  claim 5  wherein the initial water effluent is also treated with a base in an amount such that the pH of the initial water effluent is between about 8 and about 11.  
   
   
       10 . The process of  claim 5  wherein the initial water effluent is also treated with a base in an amount such that the pH of the initial water effluent is between about 9 and about 10.  
   
   
       11 . The process of  claim 5  wherein the initial water effluent is also treated with a base in an amount such that the pH of the initial water effluent is about 9.5.  
   
   
       12 . The process of  claim 1  wherein the water is introduced to the gold-recovery system at a processing step selected from the group consisting of grinding, lime slakers, exhaust scrubbers, pump gland seals, and any combination thereof.  
   
   
       13 . The process of  claim 2  wherein the initial total concentration of CN −  and SCN −  is at least about 30 ppm.  
   
   
       14 . A process for treating water for use in a gold-recovery system, wherein the water has an initial total concentration of CN −  and SCN − , the process comprising: 
 adding H 2 SO 5  to the water to yield treated water having a total treated concentration of CN −  and SCN −  which is at least 30% less than said initial total concentration of CN −  and SCN − , wherein the initial total concentration of CN −  and SCN −  is above about 30 ppm and the treated total concentration of CN −  and SCN −  is below about 20 ppm.    
   
   
       15 . The process of  claim 14  wherein the water has a total concentration of CN −  and SCN −  below about 10 ppm.  
   
   
       16 . The process of  claim 14  wherein the treated water has no detectable treated total concentration of CN −  and SCN − .  
   
   
       17 . The process of  claim 14  wherein the water having the initial total concentration of CN −  and SCN −  is reclaim water from a gold-recovery tailings pond.  
   
   
       18 . The process of  claim 14  wherein the H 2 SO 5  is added to the water in an amount greater than about 100% of the stoichiometric requirement of H 2 SO 5  necessary to react with the total initial concentration of CN −  and SCN − .  
   
   
       19 . The process of  claim 14  wherein the water further comprises a base in an amount such that the pH of the water is between about 8 and about 11.  
   
   
       20 . The process of  claim 14  wherein the water is introduced to the gold-recovery system at a processing step selected from the group consisting of grinding, lime slakers, exhaust scrubbers, pump gland seals, and any combination thereof.