This chapter highlights the latest developments in cyanidation of gold, as well as plant improvements and associated research aspects in terms of goldleaching kinetics, and surface passivation. Implementation of instrumentation for chemical monitoring and development of metallurgical reagent-addition strategies have contributed to improve the performance of cyanidation in terms of higher gold extraction and lower addition of reagents. Adequate control of oxygen and lead nitrate has proven beneficial in the optimization of leaching kinetics. This is particularly critical for increased production throughput while maintaining performance. Significant paybacks on improved gold-leaching with cyanide have been obtained. Surface analysis studies of the passive coatings formed on gold during leaching contribute to a better understanding of the mechanisms involved in gold dissolution. The findings thus indicate that these mechanisms are complex and involve electrochemical reactions, as well as mass transfer and chemical reactions.
Guy has 21 years of experience in the hydrometallurgy of gold and 2 years experience in pyrometallurgy of copper. His current work is on the development of practical applications to improve cyanidation of sulfide-bearing gold ores, leaching kinetics, plant control and reagent management as well as decreasing the toxicity of effluents. He is the author of 51 publications and 82 division and company reports and is a member of the Canadian Institute of Mining, Metallurgy and Petroleum (CIM) and the Quebec Engineering Association.