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 for**cyanidation recovery. Pressure leaching or bioleaching (oxidation) are typically used to destroy the sulfide**minerals, followed by cyanide leaching. The presence of carbonate minerals in the refractory gold ore, the**generation of partial oxidation product such as elemental sulfur during pressure leaching and bioleaching, are**detrimental to the gold recovery process due to wasteful acid and cyanide consumption. We propose to remove**these carbonate minerals and elemental sulfur by reverse flotation. For that purpose, appropriate flotation**depressants 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 the**arsenopyrite be concentrated to enrich the gold grade for subsequent processing. This usually entails the**selective separation of arsenopyrite from pyrite. Current practice is to use strong oxidation reagents to depress**arsenopyrite while floating away pyrite. Again suitable gold depressants are required if the ore contains native**gold nuggets.**In the proposed research we will utilize the phenomena of self-assembling of thiol reagents on gold surface to**guide the development of gold flotation depressants. Microflotation and batch flotation as well as atomic force**microscopic (AFM) force and induction measurements will be performed on gold powders, refractory gold**ores, and silicon wafers sputtered with gold. The flotation and force/induction time will be correlated so that**the AFM will be the primary tool to assess the effect of reagents on gold. The research will not only develop**suitable gold depressants but also suitable evaluation techniques to assess the flotation behaviors of hard-to-get**or expensive high purity minerals and precious metal powders.