There are many factors which affect the gold cyanidation mechanism – mineral composition, free cyanide and dissolved oxygen (DO) concentrations, heavy metal additions, etc. This study combines electrochemistry and surface analysis methods to examine the effectiveness of the above factors on gold cyanidation process.
Three gold ore samples were used in this study. Sample 1 was a pyrite concentrate, contained mercury and silver. Sample 2 also contained sulfide minerals, including galena. Sample 3 contained pyrite with sphalerite and galena. In the case of samples 1 and 2, the presence of heavy metals enhanced gold cyanidation kinetics, though the addition of higher DO was not effective on improving the kinetics. Sample 3 showed an opposite behavior: the kinetics was not enhanced by galena, because of its relatively small amount, however, the use of higher DO made improvement in the gold leaching kinetics, which was connected to the pyrite and sphalerite oxidation.