Optimization of Cyanide Leaching Process in order to Increase Au, Ag and Hg Recovery in Pouya Zarkan Aghdareh Plant

Cyanidation process is one of the most important and widespread hydrometallurgical technologies used in the extraction of gold and silver from ores and concentrates. Some of the most effective parameters on cyanide leaching are sodium cyanide concentration, dissolved oxygen, solid percent, pH, particle size, retention time and agitation speed. In this article the effect of these parameters on the recovery of gold, silver and mercury from Pouya Zarkan Aghdareh ore has been studied to determine the optimum conditions using Taguchi exprimental design method. The experiments at the screening step based on L16 orthogonal array indicated that the effective parameters on gold, silver and mercury recovery such as sodium cyanide, pH, solid percent in pulp, d80 and retention time were obtained equal to 900 g/t ore, 10, 42%, 53 μm and 30 h, respectively. The experiments at the optimization step based on L18 orthogonal array indicated that d80 on gold recovery and retention time on silver and mercury recovery were the most effective parameters. Finally the optimum conditions for gold, silver and mercury recovery were obtained for parameters such as sodium cyanide, pH, solid percent in pulp, d80 and retention time equal to 1000 g/t ore, 10.3, 46%, 37 μm and 40 h, respectively. At this conditions gold, silver and mercury recovery were equal to 91.42±1.02, 54.31±1.24 and 19.50±0.66 percent, respectively.