Papers by Author: Guan Zhou Qiu

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: In this work, the monitoring of bacterial and chemical dissolution of massive bornite was performed using cyclic voltammetry (CV); the mineral surface was examined using scanning electron microscopy (SEM) and the elements were indentified by Energy Dispersive X-ray Analysis (EDXA). The electrolyte employed for the electrochemical tests was the medium used for bioleaching the electrodes (3.0 g•dm-3 (NH4)2•SO4, 0.5 g•dm-3K2HPO4, 0.5 g•dm-3 MgSO4•7H2O and 0.1 g•dm-3 Ca(NO3)2).The results showed differences in voltagramms carried out by Acidithiobacillus ferrooxidans and Acidithiobacillus caldus: In bioleached electrodes tested in the presence of Acidithiobacillus ferrooxidans, the anodic and cathodic current signals were larger than with Acidithiobacillus caldus The analysis of CV results allowed attributing the different peaks observed in both the direct and reverse potential scanning to the oxidation of bornite to a secondary copper mineral(chalcocite and covellite) and its reduction via different non stoichiometric copper sulphides intermediaries. Surface evidences were produced by SEM, and chemical elements evidences were also investigated by EDAX.

Abstract: The effects of several variables on the column bioleaching of copper sulphide ore have been investigated. The copper ore contained chalcopyrite as the main sulfide minerals and bornite and chalcocite as the minor minerals. The experiment was carried out using bench-scale column leach reactors designed in Key Lab of Biometallurgy of Ministry of Education, which were inoculated with the pure mesophile bacteria (Acidithiobacillus ferrooxidans) and thermophile bacteria (Sulfobacillus), respectively, and the mixed bacteria which contain both iron- and sulfur-oxidizing bacteria. The results show that the mixed cultures were more efficient than the pure cultures alone and the maximum copper recovery 53.64% was achieved using the mixed cultures after 85 days. The leaching rate of chalcopyrite tended to increase with the increased dissolved ferric iron concentration. The effect of particle size on the rate of the copper leaching was also investigated, and it was shown that the copper bioleaching rate decreases as the amount of fines increase, which limits the permeability, thus decreases leaching rate. Jarosite and elemental sulphur formed in the column were characterized by the X-ray and EDS.

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.

Abstract: The highly conserved operon iron–sulfur cluster (iscSUA) is essential for the general biogenesis and transfer of iron–sulfur proteins in bacteria. In this study, expression, purification and characterization of the proteins of the isc operon (iscSUA) of Acidithiobacillus ferrooxidans ATCC 23270 was studied. Assembly and transfer of [Fe4S4] in vitro during the isc proteins and other iron sulfur proteins was studied in order to detect the pathway and mechanism of [Fe4S4] assembly and transfer in vivo. The [Fe4S4] cluster was successfully assembled in iron-sulfur proteins in vitro in the presence of Fe2+ and sulfide, and it was successfully transferred from IscA or IscU to iron- sulfur proteins. Our results support and extend certain models of iron-sulfur clusters assembly and transfer.

Abstract: The acidophilic heterotrophic bacteria Acidiphilium spp. were considered as a ministrant of Leptospirillum spp., Acidithiobacillus spp. and other autotrophic bacteria in acid mine drainage (AMD). 25 Acidiphilium-like bacterial strains were isolated from eight different mines in China and their physiology was characterized. Their marmatite-bioleaching ability has been investigated and compared with that of a mixed culture of Acidiphilium sp. and Acidithiobacillus ferrooxidans. The results indicated that some Acidiphilium-like strains exhibited a high marmatite-bioleaching ability, which was even higher than that of Acidithiobacillus ferrooxidans. The leaching efficiency was not higher in mixed than in pure culture. The phylogenetic relationship of the 25 Acidiphilium-like strains was analyzed by 16S rRNA sequencing, GyrB sequencing and rep-PCR genomic fingerprinting. The 25 strains and other eight species of Acidiphilium spp. were clustered into three groups.