Electrochemistry of interactions of Thiobacillus ferrooxidans with pyrite

The electrochemistry of T. ferrooxidans interactions with pyrite were studied by using a cyclic voltametry technique, and examined as a function of the fermentation stage of bacteria. The electrochemical properties of CV of the pyrite and coal-pyrite changed drastically on the second day of fermentation, when steady and convective diffusion by air bubbling diminished. The product layer was examined by SEM, X-ray diffraction and chemical analysis. The SEM study revealed that bacteria populated the pyrite surface at extremely high density levels, which, along with the solid reaction products formed on the pyrite surface created conditions for pore diffusion, explaining the CVs insensitivity to convective diffusion in solution by stirring. The X-ray diffraction study confirmed jarosite as a product layer.; The results of the transport phenomena of electrochemical charges between pyrite and iron species through the reaction product layer is evidence for the transition from i{dollar}sb{lcub}rm p{rcub}{dollar} vs. v{dollar}sp{lcub}1/2{rcub}{dollar} dependence to i{dollar}sb{lcub}rm p{rcub}{dollar} vs. v after 2 days of fermentation. This irreversible charge transfer reaction is apparently controlled by pore diffusion of the reactants through the reaction product coverages on the electrode. Using coal-pyrite, the transition from i{dollar}sb{lcub}rm p{rcub}{dollar} vs. {dollar}rm vsp{lcub}x(x=0.33){rcub}{dollar} dependence to i{dollar}sb{lcub}rm p{rcub}{dollar} vs. v{dollar}sp{lcub}1/2{rcub}{dollar} was unchanged.; Both kinetically controlled transport phenomena of electrochemical charge as a function of v exhibit a gradual process after 2 days of fermentation, resulting in several diagnostic criteria which can be explained with the same mechanistic formalism found for the transition of i{dollar}sb{lcub}rm p{rcub}{dollar} vs. v: (1) A plot of {dollar}rm Delta Esb{lcub}p{rcub}{dollar} vs. log v for the conditioned pyrite remained constant at 2 days. (2) Kinetic characteristics of charge transfer coefficients exhibited a different reaction mechanism of the {dollar}rm Fesp{lcub}2+{rcub}/Fesp{lcub}3+{rcub}{dollar} redox couple and also confirmed an agreement with the interaction mechanisms.; The environmental relationships of the conditioned pyrite affected by several solution conditions were found to be significantly sensitive to the physico-chemical nature of adhered species.; A mechanism of T. ferrooxidans cells serving as nucleation sites for jarosite formation is proposed. Finally, the complex interaction mechanisms of T. ferrooxidans with pyrite are discussed, emphasizing the mechanism of the reaction product layer growth on the pyrite surface which influenced transport phenomena of electrochemical charge.