Contribución al conocimiento sobre la minimización del consumo de Cianuro en la minería del Oro; Sales oxidantes, Aireación y Sobremolienda para minerales Cianicidas
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Rev. Bol. Quim
Abstract
La presente investigación pretende aportar al conocimiento sobre la minimización del consumo de cianuro en la minería aurífera, principalmente en minerales complejos como ser sulfuros y arseniuros de oro; con la utilización de sales oxidantes. Se realizaron ensayos de cianuración variando la concentración de cianuro, la aireación, el pH y la granulometría; se utilizaron sales de acetato de plomo y nitrato de plomo como pasivantes. En la cianuración convencional los consumos de reactivos para estos minerales son altos; la utilización de sales pasivantes resulta en una reducción de consumo de cianuro y otros reactivos, bajo los mismos parámetros de control y proceso de sobremolienda mineral. La sobremolienda (circuito cerrado de molienda) es el proceso en el cual el molino utiliza en su trabajo un clasificador cuyo producto grueso regresa al molino, y cuyo producto fino pasa a la siguiente etapa de separación. Ésta es aplicada después de la caracterización metalúrgica de la muestra por microscopía, observándose la oclusión parcial del material aurífero en matriz de pirrotita cuyo tratamiento requiere de elevadas cantidades de álcali y cianuro. Se aplicó el tratamiento con sales de plomo (sales de pasivación) que alteran superficialmente la estructura del mineral sulfurado de oro, con una disminución de la interacción con el álcali y el cianuro y consiguiente disminución en su consumo. Como resultado del proceso de cianuración con sales se obtuvo una disolución de oro del 97.78% durante 24 hs, en significativo contraste con el tratamiento convencional sin sales de pasivación que dio una disolución de oro del 84.50%. En otra experimentación de cianuración, se obtuvo una disolución de oro del 93% en 24 hs, a partir del mineral preoxidado con aire, mientras que la disolución áurica fue solo de un 80% en el mismo periodo a partir de mineral sin preoxidación. En conclusión, un mayor rendimiento de recuperación de metal precioso provino de un pre-tratamiento del mineral con sales de pasivación ó por el método de aireación, dando como resultado un buen grado de liberación de la partícula, con la consiguiente disminución en el consumo de cianuro y álcali.
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.
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.
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Vol. 36, No. 5