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dc.contributor.authorBevilaqua, Denise-
dc.contributor.authorLahti, Heidi-
dc.contributor.authorSuegama, Patrícia H.-
dc.contributor.authorGarcia Júnior, Oswaldo-
dc.contributor.authorBenedetti, Assis Vicente-
dc.contributor.authorPuhakka, Jaakko A.-
dc.contributor.authorTuovinen, Olli H.-
dc.identifier.citationHydrometallurgy, v. 138, p. 1-13.-
dc.description.abstractOxidative dissolution of chalcopyrite at ambient temperatures is generally slow and subject to passivation, posing a major challenge for developing bioleaching applications for this recalcitrant mineral. Chloride is known to enhance the chemical leaching of chalcopyrite, but much of this effect has been demonstrated at elevated temperatures. This study was undertaken to test whether 100-200 mM Na-chloride enhances the chemical and bacterial leaching of chalcopyrite in shake flasks and stirred tank bioreactor conditions at mesophilic temperatures. Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and abiotic controls were employed for the leaching experiments. Addition of Na-chloride to the bioleaching suspension inhibited the formation of secondary phases from chalcopyrite and decreased the Fe(III) precipitation. Neither elemental S nor secondary Cu-sulfides were detected in solid residues by X-ray diffraction. Chalcopyrite leaching was enhanced when the solution contained bacteria, ferrous iron and Na-chloride under low redox potential (< 450 mV) conditions. Scanning electron micrographs and energy-dispersive analysis of X-rays revealed the presence of precipitates that were identified as brushite and jarosites in solid residues. Minor amounts of gypsum may also have been present. Electrochemical analysis of solid residues was in concurrence of the differential effects between chemical controls, chloride ions, and bacteria. Electrochemical impedance spectroscopy was used to characterize interfacial changes on chalcopyrite surface caused by different bioleaching conditions. In abiotic controls, the impedance signal stabilized after 28 days, indicating the lack of changes on mineral surface thereafter, but with more resistive behavior than chalcopyrite itself. For bioleached samples, the signal suggested some capacitive response with time owing to the formation of less conductive precipitates. At Bode-phase angle plots (middle frequency), a new time constant was observed that was associated with the formation of jarosite, possibly also with minor amount or elemental S, although this intermediate could not be verified by XRD. Real impedance vs. frequency plots indicated that the bioleaching continued to modify the chalcopyrite/solution interface even after 42 days. © 2013 The Authors.en
dc.subjectElectrochemical analysis-
dc.subjectAcidithiobacillus ferrooxidans-
dc.subjectAcidithiobacillus thiooxidans-
dc.subjectEnergy dispersive analysis-
dc.subjectScanning electron micrographs-
dc.subjectConcurrency control-
dc.subjectElectrochemical impedance spectroscopy-
dc.subjectRedox reactions-
dc.subjectScanning electron microscopy-
dc.subjectX ray diffraction-
dc.subjectChlorine compounds-
dc.titleEffect of Na-chloride on the bioleaching of a chalcopyrite concentrate in shake flasks and stirred tank bioreactorsen
dc.contributor.institutionTampere University of Technology-
dc.contributor.institutionUniversidade Estadual Paulista (UNESP)-
dc.contributor.institutionUniversidade Federal da Grande Dourados (UFGD)-
dc.contributor.institutionOhio State University-
dc.description.affiliationDepartment of Chemistry and Bioengineering Tampere University of Technology, P.O. Box 541, FI-33101 Tampere-
dc.description.affiliationInstitute of Chemistry UNESP Univ. Estadual Paulista, Araraquara, SP CEP 14.901-970-
dc.description.affiliationDepartamento de Química Universidade Federal da Grande Dourados, Dourados, MS, CEP 79.825-070-
dc.description.affiliationDepartment of Microbiology Ohio State University, 484 West 12th Avenue, Columbus, OH 43210-
dc.description.affiliationUnespInstitute of Chemistry UNESP Univ. Estadual Paulista, Araraquara, SP CEP 14.901-970-
dc.rights.accessRightsAcesso aberto-
Appears in Collections:Artigos, TCCs, Teses e Dissertações da Unesp

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