Papers by Author: G. Gu

Abstract: Acidithiobacillus caldus and Leptospirillum ferriphilum cells grown in different energy substances (ferrous ion, sulfur and pyrite) were used. The adhesion of A. caldus and L. ferriphilum cells on pyrite and their effect on pyrite surface properties were studied by adsorption, zeta-potential and FT-IR methods, and the corrosion images of pyrite interaction with bacteria were examined using atomic force microscopy. Research showed that pyrite isoelectric point (IEP) after interaction with bacterial cells shifted towards cells isoelectric point, and the shift degree in case of interaction with A. caldus was observed to be much more pronounced than for interaction with L. ferriphilum, which can be due to higher affinity of A. caldus towards pyrite. The FT-IR spectra of pyrite treated with bacterial cells revealed the presence of the cell functional groups signifying cells adsorption. Although the adsorption density of A. caldus on pyrite was higher than that of L. ferriphilum, L. ferriphilum with strong ability to oxidize ferrous ion showed better leaching efficiency than A. caldus with strong ability to oxidize sulfur for pyrite leaching. The results demonstrated that more important of indirect action (L. ferriphilum) than direct action (A. caldus) on pyrite.Introduction Bacterial adsorption to minerals is an initial step in bacterial leaching for metal recovery [1]. It has been reported that bacterial adhesion is dependent not only on the biochemical properties of the organism but also on the interfacial properties of the various interfaces existing in a bioleaching system[2].The bacteria-mineral interactions result in the changes of their surface properties. The elucidation of their alternate will be beneficial for bioleaching processes. Both Acidithiobacillus caldus and Leptospirillum ferriphilum are known for their ability to inhabit acidic environments and derive energy from oxidation of inorganic substances with natural occurrence in ore deposits and acid mine drainage and high affinity towards sulfide minerals [3-5]. In this work, the alterations of surface properties of pyrite after interaction with L. ferriphilum and A. caldus are studied, and the changes in surface properties caused by bacterial adsorption are discussed with reference to bioleaching behavior of pyrite.

Abstract: For the purpose of investigations of the different situations when the cells of Acidianus manzaensis can or can not attach the surface of the chalcopyrite. Three experiments were carried out in the modified shake flasks, and in one of the experiments the cells could not attach the surface of the chalcopyrite, but could participate in the solution chemistry of the process. The redox potential, pH, cell density, copper, ion and thiosulfate concentration in the solution were monitored in the experiments, and the morphological feature and chemical composition of the leached residues were analyzed by SEM and XRD. The most leach effiency of Cu and Fe was reached in the experiment that the Acidianus manzaensis could attach the surface of the chalcopyrite. However, the unattached Acidianus manzaensis could also leach the chalcopyrite, but it was less actively than attached cells. There was no precipitation of jarosite in the leached residues of the three experiments, but there was sulfur in the leached residues when the cells could not attach the chalcopyrite. So the surface passivating layer of sulfur can be removed only when the Acidianus manzaensis can attach the surface of the chalcopyrite. From these results it become apparent that the leach of the chalcopyrite is the cooperative action of the attached and unattached Acidianus manzaensis.