Effect of mesophilic microorganisms on the electrochemical behavior of galena

In recent years, the bioleaching of sulfidic raw materials has been of grea t interest. However, the application of this biotechnology, is now very lim ited for many different complex reasons. The mechanism of the chemical and electrochemical reactions taking part in the process is not well understood The application of electrochemical techniques is useful in its elucidation . Among the common sulfides, galena has been studied very little with respe ct to its behavior during bioleaching. Therefore, the electrochemical evolu tion of massive electrodes of lead sulfide in the presence and absence of a mixed culture of mesophilic microorganisms was investigated by the applica tion of potentiometry, anodic and cathodic polarization and cyclic voltamme try. The agitation rate, the use of pH control and the composition of the n utrient mediums did not have any significant affects on the oxidation of ga lena. However, the temperature (25 degrees to 45 degrees C), the scan rate (4 to 100 mV/s) and the acid used to adjust the pH were significant variabl es that influenced sulfide oxidation. Therefore, the peak (600 to 1,000 mV) corresponding to the oxidation of sulfide ions from the mineral was only d etected ill the presence of a complexing anion of lead In the presence of b acteria, the peaks corresponding to galena oxidation decreased and, at the same time, new peaks appeared both during the oxidation at -300 mV and duri ng the reduction of the mineral surface at 150 and -300 mV. These signals w ere more important,when the attack time increased The rest potential of bio leached mineral increased with an increase ill leaching time, which I was r elated to the electrochemical transformation of the galena surface.