Method for aqueous gold thiosulfate extraction using copper-cyanide pretreated carbon adsorption
A gold thiosulfate leaching process uses carbon to remove gold from the leach liquor. The activated carbon is pretreated with copper cyanide. A copper (on the carbon) to gold (in solution) ratio of at least 1.5 optimizes gold recovery from solution. To recover the gold from the carbon, conventional elution technology works but is dependent on the copper to gold ratio on the carbon.
1. A method of recovering gold from ore containing gold, the method comprising the steps of:
treating the ore with a thiosulfate leach agent to obtain a leach solution containing gold;
pretreating activated carbon with copper cyanide to present copper cyanide on a surface of the activated carbon;
loading the pretreated activated carbon with the leach solution containing gold to adsorb gold onto the pretreated activated carbon, wherein a ratio of copper cyanide on the surface of the pretreated activated carbon to gold in the leach solution is at least about 1.5;
stripping the adsorbed gold from the pretreated activated carbon with a cyanide solution, wherein a ratio of copper and gold on the surface of the pretreated activated carbon is less than about 1.5; and
isolating the gold.
2. The method of claim 1 , wherein said activated carbon is pretreated with copper cyanide at a pH from about 9 to about 11.
3. The method of claim 2 , wherein said activated carbon is pretreated with copper cyanide at a pH of at least 10.5.
4. The method of claim 1 , wherein said pretreated activated carbon with the adsorbed gold is contacted with a cyanide solution.
5. The method of claim 1 , wherein said gold is isolated by electrowinning and smelting.