5. Conclusion
Gold and silver flotation at alkaline pH was depressed through their association with pyrite by either free cyanide or cuprous cyanide. The predominant cuprous cyanide species depressing pyrite flotation was Cu(CN)32− on a basis of thermodynamic calculation. The surface electrochemical reactions, especially the xanthate oxidation on pyrite surface were inhibited by either free cyanide or cuprous cyanide based on electrochemical studies on a pyrite electrode. The changes in the impedance characteristics of the pyrite electrode were consistent with the detachment of adsorbed xanthate species in the presence of these cyanide species, which was suggested to contribute to the hydrophilic pyrite surface and lower recovery in flotation.
Acknowledgements
The authors gratefully acknowledge the financial support of this work from Morobe Mining Joint Venture. The first author also thanks the scholarship provided by the University of Queensland.