Study on Surfactants for Passivation of Naturally Occuring Carbonaceous Matter in Gold Bearing Ores

The naturally occurring carbonaceous material (CM) in gold bearing ores often exhibits strongpreg-robbing properties. It can adversely affect the process of 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 pregrobbing have shown promising results but at the same time have demonstrated that, if not properly used, could have a strong detrimental effect on the gold recovery process. High dosages of surfactants used as passivating agents for carbonaceous matter could lead to unwanted partial passivation of the activated carbon added during the CIL process and severely impact the gold recovery. Optimal dosage for various surfactants would strongly depend on the ore mineralogy and the parameters of the pulp (temperature, pH, surface area and maturity of the carbonaceous material, etc). This paper describes an experimental study on the effectiveness of various commercially available blinding agents used to minimize the preg-robbing capacity of naturally occurring carbonaceous matter. The scope of the study was to: i) establish the optimum addition of blanking agent (surfactant) to minimize the preg-robbing capacity of the CM in the ore, and ii) establish maximum threshold amounts of blanking agents to be used before it negatively impacts the preg-robbing capacity of the activated carbon used in the CIL process. The study procedure involves standardized doping tests to evaluate the maximum pregrobbing capacity of treated CM, coupled with surface analysis with ToF-SIMS to monitor the presence and the degree of loading of these chemical surfactants on both the naturally occurring CM and the added activated carbon.