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NITROX METHOD APPLIED on REFRACTARY ORES

Abstract:

This paper summarizes the design of a process for refractory gold ores, originated from the district of Buenos Aires, Colombia. Initially applying conventional methods such as cyanide leaching, it was possible to extract approximately 65% of gold. In order to obtain gold extractions over 80% it was proposed the Nitrox method, which consists on applying nitric acid, with the goal of oxidizing the minerals containing the gold, followed by the recovery of the acid to be reused in the process. The process started with the mineral characterization of 2 samples (A and B) of the mine Carmelo, using optical techniques, petrography and mineralogy, employing polished thin sections, and polished sections observing sulfide minerals as pyrite, chalcopyrite which cause the refractoriness. The sample preparation starts with fine grinding until reaching a size under 40 µm, then proceeding to the oxidation, washing, filtration, cyanide leaching and tail analysis. The results obtained, applying the method, were increasing the percentage of gold extraction for sample A from 75.89% to 95.87% and for sample B from 62.68% to 85.16% depending on parameters such as acid concentration, time of acid exposure and time of the cyanide leaching.