Influence of thermophilic microorganisms on the electrochemical behavior of pyrite

The electrochemical behavior of massive pyrite (FeS2) electrodes has been s tudied in the absence and in the presence of thermophilic (moderate and ext reme) microorganisms using potentiometry, anodic and cathodic polarization and cyclic voltammetry as analytical techniques. The cultures used were mod erate and extreme thermophilic microorganosm. First of all, the bacteria cultures were adapted to pyrite. Next, the influ ence of some physical and chemical factors such as agitation, temperature, scan rate, pH and different nutrient media (9K, Norris and sulfuric acid) w as studied in the absence of bacteria. Temperature, scan rate and pH were s ignificant variables influencing the sulfide oxidation. The results showed that in the presence of bacteria the rest potential of t he bioleached mineral increased with the leaching time which was related to the electrochemical transformation of the pyrite surface. The pyrite bioleached showed three new signals in the voltammetric scan, on e of them corresponding to an oxidation and the other two to reductions. Th ese signals were more important when the attack time increased.