Development of gold flotation depressants for refractory gold ores

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Most refractory gold ores need to be treated to destroy the encapsulating sulfide minerals to release the gold forcyanidation recovery. Pressure leaching or bioleaching (oxidation) are typically used to destroy the sulfideminerals, followed by cyanide leaching. The presence of carbonate minerals in the refractory gold ore, thegeneration of partial oxidation product such as elemental sulfur during pressure leaching and bioleaching, aredetrimental to the gold recovery process due to wasteful acid and cyanide consumption. We propose to removethese carbonate minerals and elemental sulfur by reverse flotation. For that purpose, appropriate flotationdepressants for gold are required, which are not currently available.In refractory gold ores the gold is typically associated with arsenopyrite. Often it is required that thearsenopyrite be concentrated to enrich the gold grade for subsequent processing. This usually entails theselective separation of arsenopyrite from pyrite. Current practice is to use strong oxidation reagents to depressarsenopyrite while floating away pyrite. Again suitable gold depressants are required if the ore contains nativegold nuggets.In the proposed research we will utilize the phenomena of self-assembling of thiol reagents on gold surface toguide the development of gold flotation depressants. Microflotation and batch flotation as well as atomic forcemicroscopic (AFM) force and induction measurements will be performed on gold powders, refractory goldores, and silicon wafers sputtered with gold. The flotation and force/induction time will be correlated so thatthe AFM will be the primary tool to assess the effect of reagents on gold. The research will not only developsuitable gold depressants but also suitable evaluation techniques to assess the flotation behaviors of hard-to-getor expensive high purity minerals and precious metal powders.