Recovery of gold from carbonaceous gold-bearing ores

摘要

When certain sedimentary gold ores containing indigenous organic carbonaceous materials are slurried with an aqueous solution containing an alkali metal cyanide, the aurocyanide complex which is formed is adsorbed by an adsorptive carbon component of the ore. Dissolution of the gold proceeds until chemical equilibrium is attained between the aurocyanide complex in solution and the aurocyanide complex adsorbed by the ore. In the process of the invention, the gold is dissolved from the ore by using (1) much higher strengths of cyanide solution, and (2) much higher temperatures than are normally used in the standard cyanidation process, allowing higher extractions of gold to take place. Because the concentration of aurocyanide in solution is limited by chemical equilibrium, the dissolution of gold must be done in stages. An amount of granular activated carbon substantially greater than the amount of indigenous active carbon present in the ore is added to each stage of dissolution, the added carbon and the carbon in the ore both adsorbing the aurocyanide complex until the system comes to equilibrium. The added carbon is separated from the ore slurry after each stage, and the reaction is repeated in successive stages of extraction. The added carbon separated from the ore slurry is treated to remove and recover the gold complexes adsorbed thereon.