Preg-robbing phenomena in the cyanidation of sulphide gold ores

The study investigates the preg-robbing phenomena of pyrite and chalcopyrite in the cyanidation of sulphide gold ores. The objective is to examine how these minerals adsorb gold in cyanide-deficient solutions, both with and without activated carbon. A series of experiments were conducted to determine the extent of gold removal from solution by these ores. Results showed that chalcopyrite exhibited strong preg-robbing characteristics, competing effectively with activated carbon to extract gold. Pyrite also displayed significant preg-robbing behavior, preferentially adsorbing gold over activated carbon in cyanide-poor environments. The adsorption degree was influenced by the kinetics of the process. Furthermore, the study explored the impact of copper, silver, zinc, nickel, and iron cyanide complexes, highlighting their role in mitigating preg-robbing and stabilizing the aurocyanide complex. The findings reveal that the ability of sulphide ores to adsorb Au(CN)₂⁻ is linked to their cyanide consumption rate and the formation of metal-cyanide complexes. A proposed mechanism suggests the reduction of gold at chalcopyrite surfaces leads to new copper-cyanide complexes, while similar reductions occur at pyrite surfaces with zinc as an impurity.