Reducing preg-robbing in carbonaceous gold ores using passivative or blanking agents

Abstract

Carbonaceous materials found in gold ores often exhibits strong preg-robbing properties which adversely affect gold recovery during the cyanidation due to its ability to adsorb, or preg-rob gold from the cyanide leach solution. Treatments of carbonaceous ores with chemical surfactants as blinding agents to limit preg-robbing have shown promising results however, if not properly used, could have a strong detrimental effect on the gold recovery process. The present study investigated the effectiveness of using commercially available surfactants (Dextrin, naphthalene sulphonate and Triton X-100) as blanking agents to minimize the preg-robbing capacity of various carbonaceous materials (activated carbon, anthracite and bituminous) and carbonaceous gold ore through adsorption and leaching studies. Chemical analysis of ore sample used for the study showed that the gold (Au) content was 17.2 g/t. The organic carbon content of the ore sample was 0.95%. Mineralogical composition of the ore sample determined with X-ray diffraction (XRD) showed that pyrite (24.8%), Quartz (21.5%) and Muscovite (21.8%) were the main mineral in the ore. Gold adsorption studies performed revealed that the treatment of the carbonaceous materials (activated carbon, anthracite and bituminous) with the blanking reagents significantly decrease gold adsorption by the carbonaceous materials. However, the blanking ability for the surfactant varied for the various carbonaceous materials. Application adsorption studies to gold leaching test confirmed that the three surfactants, especially naphthalene sulphonate could be used as blanking agents for carbonaceous gold ores during cyanidation. Gold recovery from CIL studies increased from 46.0% to 67.7%, 52.3% and 49.0% after treatment with naphthalene sulphonate, dextrin and triton X-100 (49.0%) respectively.