Experimental Study On Leaching Gold From Cyanide Tailings

Cyanide residues are the solid wastes produced in cyanide process of gold roasted concentrate,in which the content of gold and silver is 0.2g/t-10g/t and 25g/t-90g/t, respectively, which have great values of recycling and utilization. However, it’s difficult to recover gold from cyanide residues because gold is encapsulated by iron mineral. To recovery gold from cyanide residues have great economic benefits and can enhance the comprehensive utilization ratio of resources for gold plant.Using the cyanide residues of a domestic gold smelter as raw material, the experimental studies were carried out to leach gold from cyanide residues by the process of sulfuric acid leaching iron-thiourea leaching gold.And the optimum parameters were obtained,which can provide the theoretical basis for industrial application.The extraction method of gold and the status of recovering gold from cyanide residues were reviewed. The research method of sulfuric acid leaching iron-thiourea leaching gold was put forward.The theoretical analysis of removing iron from cyanide residues by sulfuric acid leaching and leaching gold by thiourea were conducted and the experiments were carried out systematically. The effects of sulfuric acid dosage, leaching temperature,leaching time, liquid-solid ratio on leaching ratio of iron were studied. The optimum terms of removing iron by sulfuric acid leaching were obtained as follows,sulfuric acid dosage is 45ml concentrated sulfuric acid for 100g cyanide tailings, leaching temperature is 80℃, leaching time is 4h, liquid-solid ratio is 4:1.Under those terms, the verification experiments of sulfuric acid leaching were carried out and the results showed that the average leaching ratio of iron can be reached to 60.29%.The acid leaching residues were obtained under those optimum terms of acid leaching iron above.Using the acid leaching residues as raw material, experiments of leaching gold by thiourea were carried out. The effects of thiourea dosage, leaching temperature, leaching time on leaching ratio of gold were researched.The optimum terms of leaching gold by thiourea were gained as follows, thiourea dosage is 25kg/t, leaching temperature is 50 ℃, leaching time is 4h. The verification experiments of leaching gold by thiourea were studied under those conditions above and the results showed that the average leaching ratio of gold can be reached to 62.33%.The comprehensive verification experiments of sulfuric acid leaching iron-thiourea leaching gold were carried out under those terms above, the results showed that the average leaching ratio of iron was 60.61% and the average leaching ratio of gold was 63.05%.The process has the advantages of short flow sheet and low energy consumption, with which gold can be leached effectively from cyanide residues, which has better prospect for industrial application.