Electrochemical Study of the Chalcopyrite Biooxidation in Presence and Absence of Sulfuro- and Ironoxidizing Microorganisms
Iron and sulfur oxidizing microorganisms (IOM and SOM, respectively) may prevent such effect throughout the biooxidation of reduced sulfur species [8, 9]. It has been found that the electrochemical formation of S° and Sn2- phases on mineral surface facilitates initial attachment of microorganisms; in addition, it has been reported that the electrochemical activity degree of sulfur species, directly influences on the physicochemical and biological characteristics of the biofilm developed during the biooxidation[10,11]. This research assessed the biooxidation process of CuFeS2, correlating the initial presence of S° and/or Sn2- with changes in the hydrophobic domains (HD) of extracellular polymeric substances (EPS) of the formed biofilm. For this, the behavior of two different microbial cultures were compared, one SOM culture (containing only Acidithiobacillus thiooxidans) and a mixed SOM-IOM culture (Acidithiobacillus thiooxidans + Leptospirillum sp.). Massive Electrodes of chalcopyrite were electrochemically oxidized to form the sulfur secondary species (S° and Sn2-) previous to the mineral-bacteria contact. The evolution of secondary [RL1] species during biooxidation process in each culture was followed by Raman Spectroscopy. The spacetime changes of the biofilm and interfacial electrochemical study were evaluate by Electrochemical Impedance Spectroscopy (EIS and Scanning Electron Microscopy (SEM). The previous results showed that there are important differences in the biooxidation process, depending on the sulfur species produced initially, the type of culture used, and the incubation time; in addition, it was found that both types of cultures efficiently remove S° and Sn2- by dissimilar mechanisms that seem to be associated with the IOM role in the bioleaching process.
Key Words chalcopyrite, passivation layer, IOM, SOM, biooxidation.
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