Conventional and electrochemical bioleaching of chalcopyrite concentrates by moderately thermophilic bacteria at high pulp density

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dc.contributor.authorAhmadi, Ali
dc.contributor.authorSchaffi, Mahine
dc.contributor.authorPetersen, Jochen
dc.contributor.authorSchippers, Axel
dc.contributor.authorRanjbar, Mohammad  
dc.date.accessioned2016-08-17T10:28:12Z
dc.date.available2016-08-17T10:28:12Z
dc.date.issued2011
dc.date.updated2016-08-17T10:27:03Z
dc.description.abstractConventional and electrochemical bioleaching were investigated to extract copper from Sarcheshmeh chalcopyrite concentrate at high pulp densities. Experiments were conducted in the presence and absence of a mixed culture of moderately thermophilic iron- and sulphur oxidizing bacteria using a 2-L stirred electro-bioreactor at 20% (w/v) pulp density, an initial pH of 1.4–1.6, a temperature of 50 °C, a stirring rate of 600 rpm and Norris nutrient medium with 0.02% (w/w) yeast extract addition. The results of 10 day leaches showed that, when using electrochemical bioleaching in an ORP range of 400 to 430 mV, copper recovery reaches about 80% which is 3.9, 1.5 and 1.17 times higher than that achieved in abiotic electrochemical leaching, conventional bioleaching, and electrochemical bioleaching at 440–480 mV ORP, respectively. It appears that applying current directly to the slurry optimises both, the biological and chemical subsystems, leading to an increase in both, the dissolution rate and the final recovery of copper from the concentrate. Mineralogical analysis of the solid residues of electrochemical leaching in both, biotic and abiotic media, showed the formation of chalcocite and covellite minerals on the surface of not leached chalcopyrite. It is postulated that the reduction of refractory chalcopyrite to more soluble minerals such as chalcocite and covellite is achieved through both, electron transfer upon electrode contact and by ferrous reduction at the low ORP of the slurry. These secondary minerals are then rapidly dissolved through bioleaching, while at the same time a formation of a passive layer of jarosites is minimised. This process also appears to promote an increased bacteria–solid ratio due to favourable growth conditions.en_ZA
dc.identifierhttp://dx.doi.org/10.1016/j.hydromet.2010.12.007
dc.identifier.apacitationAhmadi, A., Schaffi, M., Petersen, J., Schippers, A., & (2011). Conventional and electrochemical bioleaching of chalcopyrite concentrates by moderately thermophilic bacteria at high pulp density. <i>Hydrometallurgy</i>, http://hdl.handle.net/11427/21292en_ZA
dc.identifier.chicagocitationAhmadi, Ali, Mahine Schaffi, Jochen Petersen, Axel Schippers, and "Conventional and electrochemical bioleaching of chalcopyrite concentrates by moderately thermophilic bacteria at high pulp density." <i>Hydrometallurgy</i> (2011) http://hdl.handle.net/11427/21292en_ZA
dc.identifier.citationAhmadi, A., Schaffie, M., Petersen, J., Schippers, A., & Ranjbar, M. (2011). Conventional and electrochemical bioleaching of chalcopyrite concentrates by moderately thermophilic bacteria at high pulp density. Hydrometallurgy, 106(1), 84-92.en_ZA
dc.identifier.issn0304-386Xen_ZA
dc.identifier.ris TY - Journal Article AU - Ahmadi, Ali AU - Schaffi, Mahine AU - Petersen, Jochen AU - Schippers, Axel AU - Ranjbar, Mohammad   AB - Conventional and electrochemical bioleaching were investigated to extract copper from Sarcheshmeh chalcopyrite concentrate at high pulp densities. Experiments were conducted in the presence and absence of a mixed culture of moderately thermophilic iron- and sulphur oxidizing bacteria using a 2-L stirred electro-bioreactor at 20% (w/v) pulp density, an initial pH of 1.4–1.6, a temperature of 50 °C, a stirring rate of 600 rpm and Norris nutrient medium with 0.02% (w/w) yeast extract addition. The results of 10 day leaches showed that, when using electrochemical bioleaching in an ORP range of 400 to 430 mV, copper recovery reaches about 80% which is 3.9, 1.5 and 1.17 times higher than that achieved in abiotic electrochemical leaching, conventional bioleaching, and electrochemical bioleaching at 440–480 mV ORP, respectively. It appears that applying current directly to the slurry optimises both, the biological and chemical subsystems, leading to an increase in both, the dissolution rate and the final recovery of copper from the concentrate. Mineralogical analysis of the solid residues of electrochemical leaching in both, biotic and abiotic media, showed the formation of chalcocite and covellite minerals on the surface of not leached chalcopyrite. It is postulated that the reduction of refractory chalcopyrite to more soluble minerals such as chalcocite and covellite is achieved through both, electron transfer upon electrode contact and by ferrous reduction at the low ORP of the slurry. These secondary minerals are then rapidly dissolved through bioleaching, while at the same time a formation of a passive layer of jarosites is minimised. This process also appears to promote an increased bacteria–solid ratio due to favourable growth conditions. DA - 2011 DB - OpenUCT DP - University of Cape Town J1 - Hydrometallurgy LK - https://open.uct.ac.za PB - University of Cape Town PY - 2011 SM - 0304-386X T1 - Conventional and electrochemical bioleaching of chalcopyrite concentrates by moderately thermophilic bacteria at high pulp density TI - Conventional and electrochemical bioleaching of chalcopyrite concentrates by moderately thermophilic bacteria at high pulp density UR - http://hdl.handle.net/11427/21292 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/21292
dc.identifier.urihttp://www.sciencedirect.com/science/article/pii/S0304386X10003191
dc.identifier.vancouvercitationAhmadi A, Schaffi M, Petersen J, Schippers A, . Conventional and electrochemical bioleaching of chalcopyrite concentrates by moderately thermophilic bacteria at high pulp density. Hydrometallurgy. 2011; http://hdl.handle.net/11427/21292.en_ZA
dc.languageengen_ZA
dc.publisherElsevieren_ZA
dc.publisher.institutionUniversity of Cape Town
dc.sourceHydrometallurgyen_ZA
dc.source.urihttp://www.sciencedirect.com/science/journal/0304386X
dc.subject.otherElectrochemistry
dc.subject.otherBioleaching
dc.subject.otherElectro-bioreactor
dc.subject.otherChalcopyrite
dc.subject.otherModerately thermophilic bacteria
dc.titleConventional and electrochemical bioleaching of chalcopyrite concentrates by moderately thermophilic bacteria at high pulp densityen_ZA
dc.typeJournal Articleen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceArticleen_ZA
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