Selective gold extraction from copper anode slime with an alcohol

Abstract

The invention relates to a method for recovering gold from an acid digest of a gold-containing copper anode slime. The acid digest is selectively extracted with an alcohol having low miscibility with water. Gold is then recovered from the resulting alcoholic extract.

1 . A method for recovering gold from an acid digest of a gold-containing copper anode slime, said method comprising:
 a) selectively extracting the acid digest with an alcohol to form an alcoholic extract comprising the gold, said alcohol having low miscibility with water; and   b) recovering the gold from the alcoholic extract; wherein the gold in the acid digest is in a form that is extractable into said alcohol.   
     
     
         2 . The method of  claim 1  wherein the alcohol has a solubility in water of less than about 0.2% w/w, v/v or w/v at 20° C. 
     
     
         3 . The method of  claim 1  wherein the alcohol is a primary alcohol. 
     
     
         4 . The method of  claim 3  wherein the primary alcohol is a branched chain alcohol. 
     
     
         5 . The method of  claim 4  wherein the branched chain alcohol is selected from the group consisting of 2-ethyl-1-hexanol, 8-methyl-1-nonanol and mixtures thereof. 
     
     
         6 . The method of  claim 1  further comprising digesting a gold-containing copper anode slime using acid to provide the acid digest. 
     
     
         7 . The method of  claim 6  wherein said digesting comprises combining the anode slime with concentrated hydrochloric acid. 
     
     
         8 . The method of  claim 6  wherein an oxidant is used with the acid in digesting the gold-containing copper anode slime. 
     
     
         9 . The method of  claim 1  wherein the acid digest comprises a radioactive element and the acidity of the acid digest is such that at least about 90% of the gold present in the digest is extracted into the alcohol and less than about 10% of the amount of the radioactive element present in the acid digest is extracted into the alcohol. 
     
     
         10 . The method of  claim 9  wherein the radioactive element is polonium. 
     
     
         11 . The method of  claim 1  wherein the proportion of gold to total metals in the acid digest prior to step-a) is about 4% or less by weight or by moles. 
     
     
         12 . The method of  claim 1  wherein a) comprises continuous countercurrent extraction. 
     
     
         13 . The method of  claim 1  further comprising scrubbing the alcoholic extract to remove impurities from said extract, said scrubbing being conducted between a) and b). 
     
     
         14 . The method of  claim 13  wherein said scrubbing comprises scrubbing with a dilute mineral acid. 
     
     
         15 . The method of  claim 1  wherein b) comprises extracting the alcoholic extract with an aqueous extractant to provide a gold-containing aqueous extract. 
     
     
         16 . The method of  claim 15  wherein the aqueous extractant has a pH greater than about 5. 
     
     
         17 . The method of  claim 16  wherein the aqueous extractant is at approximately neutral pH. 
     
     
         18 . The method of anyone of  claim 15  further comprising of reducing the gold in the aqueous extract to Au(0). 
     
     
         19 . The method of  claim 18  comprising further refining the Au(0). 
     
     
         20 . The method of  claim 1  wherein the gold in the acid digest is present as Au(III). 
     
     
         21 . The method of  claim 20  wherein the gold in the acid digest is present as AuCl4 − . 
     
     
         22 . The method of  claim 1  further comprising recovering the alcohol from the alcoholic extract. 
     
     
         23 . The method of  claim 22  wherein the recovered alcohol is reused in step a). 
     
     
         24 . (canceled) 
     
     
         25 . (canceled) 
     
     
         26 . (canceled) 
     
     
         27 . (canceled) 
     
     
         28 . (canceled) 
     
     
         29 . The method of  claim 8  wherein the oxidant is hydrogen peroxide or chlorine.