Leaching of finely disseminated gold ore with cyanide and thiourea solutions

In this study, the aim was to investigate the gold recovery from finely disseminated ore by using thiourea as an alternative to the cyanidation process. Experimental studies were carried out on the Gumushane-Mastra (East Black Sea Region, Turkey) epithermal ore samples, which contain finely disseminated gold. The effects of parameters such as grinding particle size, mixing time, extractant and oxidant concentrations, and pH on agitation leaching were examined for both methods and the reagent consumption values under satisfactory conditions were determined. The experimental results were compared with respect to consumed reagent amounts and technological efficiencies, and it was revealed that cyanidation is more advantageous. Gold recovery decreases and a higher reagent consumption is required for thiourea treatment. In leaching, using thiourea and increasing oxidant content and mixing time improved the process up to a certain level. Elemental sulfur formation and adsorption hindered diffusion. Thus, leaching extent higher than 78% could not be obtained. (C) 2003 Elsevier Science B.V. All rights reserved.