Abstract

HUAMANI B, Roberto P et al. Contribution to the knowledge about minimization of cyanide consumption in gold mining; oxidizing salts, aeration and overmolding for cyanicide minerals . Rev. Bol. Quim [online]. 2019, vol.36, n.5, pp.190-197. ISSN 0250-5460.

Abstract This research aims to contribute to the knowledge about the minimization of cyanide consumption in gold mining, mainly in complex minerals such as gold sulphides and gold auroarseniides; with the use of oxidizing salts. Cyanidation assays were performed varying the cyanide concentration, aeration, pH and particle size; salts of lead acetate and lead nitrate were used as passivants. In conventional cyanidation the reagent consumptions for these minerals are high; the use of passivating salts results in a reduction in the consumption of cyanide and other reagents, under the same control parameters and mineral overmolding process. Overmolding (closed milling circuit) is the process in which the mill uses a classifier whose thick product returns to the mill, and whose fine product passes to the next separation stage. This is applied after the metallurgical characterization of the sample by microscopy, observing the partial occlusion of the gold material in pyrrhotite matrix whose treatment requires high amounts of alkali and cyanide. The treatment with lead salts (passivation salts) that superficially alter the structure of the gold sulphide mineral was applied, with a decrease in the interaction with alkali and cyanide and consequent decrease in its consumption. As a result of the cyanidation process with salts, a gold solution of 97.78% was obtained for 24 hours, in significant contrast to the conventional treatment without passivation salts that gave a gold solution of 84.50%. In another cyanidation experiment, a gold solution of 93% was obtained within 24 hours, from the ore pre-oxidized with air, while the auric solution was only 80% in the same period from ore without pre-oxidation. In conclusion, a higher recovery yield of precious metal came from a pre-treatment of the mineral with passivation salts or by the aeration method, resulting in a good degree of particle release, with the consequent decrease in the consumption of cyanide and alkali.

Keywords : : Cyanidation; Gold, ; Oxidation; Passivation.

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