The Mechanism of the Ammonia-Cyanide System for Leaching Copper-Gold Ores

Muir, David M. ; Deng, Tong ; La Brooy, Stephen R. ; Monhemius, A. J. ; Peters, E. ; Singh, Pritam ; Warren, G. W.
Organization: Society for Mining, Metallurgy & Exploration
Pages: 14
Publication Date: Jan 1, 1993
The controlled addition of ammonia to cyanide solutions inhibits the leaching of copper minerals but extracts up to 80% Au using as little as 10% of the cyanide compared with conventional cyanidation of copper-gold ores. The solubility of copper minerals and copper speciation in solution is dependent on NH3, CN-, pH and Eh. Rotating disc and electrochemical studies show that gold is leached by a mixed Cu-CN--NH3 complex with either Cu(II) or O2 as oxidant. This complex is slowly oxidised to CuCN and Cu(OH)2 by air.
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