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Cyanide leaching of gold is a common step used in the separation between gold concentrate and gangue minerals. Generally, the common gold extraction processes mainly include gravity separation, flotation, magnetic separation and electric separation, and the low grade gold concentrate obtained by the above gold extraction processes can be further processed using cyanidation method.
Au is a physically and chemically element, which is existed in nature as simple substance except for aqua regia. KCN, the common cyaniding leaching raw material, which is referred in 3 theories about the cyanide leaching of gold:
4Au + 8KCN + O2 + 2H2O = 4KAu(CN)2 + 4KOH
Isner thought that KCN, dissolved oxygen, and water react with gold in water, and integrate into solution as the shape of a complex.
2Au + 4KCN+ O2+2H2O = 2KAu(CN)2+2KOH+H2O2 ,2Au + 4KCN+H2O2= 2KAu(CN)2+2KOH
This theory holds the view that gold integration into cyanide in two steps together with the processing of producing hydrogen peroxide, which has the same equation with the oxygen theory.
This theory holds the view, the cyanide leaching of gold is an electronic corrosion processing. There is electronic current within the gold particle. So, there is positive zone having positive electronics and a negative zone having negative electronics. Cyanide leaching of gold is the processing positive Au losing electronics and becoming the negative electronics. Dissolved oxygen obtains electronics and react with water and producing dissolved peroxide and OH.
The above the is principle of cyanide leaching of gold. However, cyanide is poisonous which will be highly harmful to the environment in the cyanide leaching of gold. So, in the view of the environmental perspective, we should use environmental-friendly gold leaching solution or find the eco-friendly subsitutes of sodium cyanide for gold leaching.
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