Analysis of the Oxidation-Reduction Potential and Bacterial Population of <em>Acidithiobacillus ferrooxidans</em> during the Bioleaching Study of Sulfide Ores

The analysis of the variables, bacterial population, and oxidation-reduction potential (ORP) during the bioleaching of sulfide ores by a bacterial strain of Acidithiobacillus ferrooxidans, isolated from acid mine effluent, aims at the solubilization of copper and the liberation of the gold present in an ore containing more than 80% sulfides. It was studied at different pulp densities (1, 2, and 6% - W/V) and with a 9 k medium at different ferrous sulfate concentrations (0, 3, 6, 9, 12, and 15 g/L), keeping temperature and pH constant. The tests were carried out in three consecutive stages, starting with inoculum, whose cell content was 7.05x107 Cell/mL, then the strain with the highest population obtained in the previous stage was used, observing the variation in the periods of adaptation and growth. During the bioleaching of sulfide ores, in the first stage, the maximum bacterial population achieved was 4.75x107 Cell/mL in 24 days with 6 g/L ferrous sulfate, in the second stage, the maximum population was 6.30x107 Cell/mL without the addition of ferrous sulfate, and in the third stage, the bacterial population became 4.51x107 Cell/mL. The exponential characteristic growth of the population started at approximately 13, 8, and 3 days, respectively in each stage