Experimental study on alkaline pressure pre-oxidation-cyanide leaching of low-grade carbonaceous gold ore in Hubei Province
The gold grade of a tailings sample in Hubei is 0.325 g/t,with a carbon content of 0.49%,belonging to typical low-grade carbonaceous gold ore.The mineralogy indicates that the main minerals in the ore are quartz,kaolinite,and illite,with 79.59%of carbon distributed in organic carbon.Various leaching processes such as direct cyanide leaching,surface passivation-cyanide leaching,competitive adsorption-cyanide leaching,and chemical oxi-dation pre-treatment-cyanide leaching were employed,but the gold leaching rates were all less than 20%.The preg-robbing performance test shows that the tailings have a preg-robbing index of 1.462 g/t,belonging to the medium preg-robbing category.The alkaline pressure pre-oxidation process significantly reduced the carbonaceous preg-robbing effect and increased gold leaching efficiency.Under specific conditions of grinding fineness at-0.074 mm with80%distribution,oxygen pressure of 1 000 kPa,liquid-solid ratio of 2∶1,sodium hydroxide dosage of 5%,and pressure pre-oxidation time of 6 h at an agitation rate of 200 r/min,the gold leaching rate reached 64.15%by alkaline pres-sure pre-oxidation-cyanide leaching.
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