Determinación de la capacidad oxidativa de un consorcio microbiano nativo sobre un mineral aurífero refractario

Abstract

Biooxidation is known as an alternative process (pre-treatment) for gold recovery from refractory ores, which had increased in developing countries. This process uses acidophilic microorganisms, which allows the gold presetn in a sulfurized ore matrix become available for the cyanidation process. This research had two main goals which were to isolate the native acidophilic microorganism from a natural acidic drainage and to determine its oxidation capacity in a stirring tank reactor by varying the pulp density (% w/v) to get better solubility of the mineral and greater gold recovery. For the isolation of acidophilic microorganisms, a Silverman and Lundgren (1959) medium culture adjusted to pH 1.8 was used; ferrous sulfate (FeSO4 * 7H2O) was used as an energy source. For the adaptation of these microorganisms and in order for them to reach optimal growing rates (u), successive cell replications were performed at the time the color of the culture changed from green to red. The biooxidation tests were conducted by using the following fixed variables: pH (1, 8), temperature (20°C), agitation (400rpm), aeration (3vvm), initial inoculum concentration (20%v/v), particle size (-200mesh) and four pulp densities (5, 10, 15 and 20 %w/v). The concentration of Fe, total Fe, sulfates and cell counting in a Neubauer chamber were measured for a 30-day period to determinate the microorganism growing kinetics during the oxidation process. The volumetric productivity obtained in the biooxidation process per batch was: Qp Fe of 2.20, 1.65, 0.80, 0.78 g/L day; Qp SO4 of 3.17, 2.27, 2.10, 1.73 g/L day and the gold recovery values were 51, 40, 33 and 43% for pulp densities of 5, 10, 15 and 20 % w/v, respectively. Key wordsacidophilic microorganism, biooxidation, gold recovery, refractory minerals, volumetric productivity.