Selectivity considerations in the amine extraction of gold from alkaline cyanide solutions

It has been discovered that gold can be extracted from alkaline cyanide solution with primary, secondary, and tertiary amines by adding certain Lewis base modifiers, such as organic phosphorus oxides. Under these circumstances, gold can be extracted at about pH 10, commensurate with the pH of cyanide leach liquors. The selectivity of the amines and amine/modifier combinations for Au(CN)~2 over other metal-cyanide complexes is discussed. Potential applications for the solvent extraction of gold from cyanide solutions are also discussed.