111 WORLD GOLD CONFERENCE / BRISBANE, QLD, 26 - 29 SEPTEMBER 2013 INTRODUCTION Ubiquitous occurrence of copper and sulide minerals in ores is known to have a negative impact on the extraction of precious metals by cyanidation, mainly due to the high consumption of reagents. Research reveals that the successful application of cyanidation depends not only on the dissolution behaviour of precious metals but also on the behaviour of the associated minerals (Bayat et al, 2003) and (Azizi et al, 2010). Preoxidation (PO) of the sulide minerals could result in the formation of several oxy-sulfur species, leading the encapsulated precious metal to be amenable to a cost-effective cyanidation. Applying additives in leaching could also limit the reactivity of basic metals (Cu, Zn, etc) and ameliorate the cyanidation of precious metals. In recent years, different oxidising agents have been tested in both PO and cyanidation (Bayat et al, 2003; Xie and Dresinger, 2009; Breuer, Hewitt and Meakin, 2008; Ellis and Optimisation of Operating Parameters for Cyanidation of Sul ide-Bear ing Gold Flotation Tailings in order to Prevent the Impact of Cyanicides E Ghasemian Langeroudi 1 , B Levasseur 2 , F Saizadeh 3 , C Olsen 4 , F Larachi 5 and C Gagnon 6 ABSTRACT Gold recovery by the cyanidation process is often accompanied by the leaching of other species. This leads to the depletion of the level of free cyanide and oxygen available for gold cyanidation. The largest proportion of the consumed cyanide is diverted by the cyanicides (eg S, Cu, Zn, Fe, etc) into non-valuable complexes. COREM’s Extractive Metallurgy team has been conducting a research program on the improvement of the gold cyanidation process. As a part of this program, the current study aims to investigate the effect of certain operating parameters on the reactions involved during preoxidation and cyanidation. Flotation tailings and single mineral samples such as pyrite, sphalerite and chalcopyrite, along with their different combinations, were analysed to highlight the inluence of ore mineralogy on the operating conditions. The effects of different kinds of oxidants (oxygen, hydrogen peroxide, ferricyanide and ozone) and chemical additives (ammonium sulfate) were investigated. Experiments conducted in alkaline solutions reveal that mineralogy is a key parameter since pyrite, chalcopyrite and sphalerite react quite differently during preoxidation and cyanidation. A signiicant increase in sulfur dissolution, especially on pyrite, was observed by applying preoxidation. H 2 O 2 preoxidation showed a positive effect on increasing sulfate formation, a desirable by-product from the cyanide consumption point of view. Preoxidation of synthetic ores with ferricyanide resulted in boosting thiosulfate formation. Tests conducted on lotation tailings from a polymetallic mine revealed that a short preoxidation increases the dissolution of the ore leading to higher gold recovery and lower cyanide consumption. Regarding the formation of thiocyanate, the most undesirable by-product of the cyanidation, ferricyanide and ozone were found particularly eficient to hinder their formation. Finally, the addition of ammonium sulfate during the cyanidation process showed some promising results in terms of both gold dissolution and cyanide consumption. 1. Researcher, COREM, 1180 rue de la Minéralogie, Québec Qc G1N 1X7, Canada. Email: ghasemian.el@gmail.com 2. Researcher, COREM, 1180 rue de la Minéralogie, Québec Qc G1N 1X7, Canada. Email: benoit.levasseur@corem.qc.ca 3. Postdoctoral Researcher, COREM, 1180 rue de la Minéralogie, Québec Qc G1N 1X7, Canada. Email: fariba.saizadeh.1@ulaval.ca 4. Program Leader – Flotation and Extractive Metallurgy, COREM, 1180 rue de la Minéralogie, Québec Qc G1N 1X7, Canada. Email: caroline.olsen@corem.qc.ca 5. Professor, Université Laval, Chemical Engineering Department, Faculté des sciences et de génie, Pavillon Adrien-Pouliot, 1065, av de la Médecine, local 3550, Université Laval, Québec Qc G1V 0A6, Canada. Email: faical.Larachi@gch.ulaval.ca 6. Director – Non-Ferrous Sector, COREM, 1180 rue de la Minéralogie, Québec Qc G1N 1X7, Canada. Email: claude.gagnon@corem.qc.ca