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Zhao H.,Key Laboratory of Biohydrometallurgy of Ministry of Education | Wang J.,Central South University | Yang C.,Key Laboratory of Biohydrometallurgy of Ministry of Education | Hu M.,Key Laboratory of Biohydrometallurgy of Ministry of Education | And 4 more authors.
Hydrometallurgy | Year: 2015

Thermodynamic calculations and electrochemical measurements were employed to establish a mathematic model for predicting the optimum redox potential in chalcopyrite leaching at 318 K. The proposed model revealed that the optimum redox potential mainly depended on the temperature as well as the concentrations of Cu2 + and Fe2 +. Chemical leaching (ferric leaching) of chalcopyrite indicated that the proposed model was accurate, from which the optimum redox potential of bioleaching of chalcopyrite can also be accurately predicted. Based on the model, the redox potential should be maintained at an optimum potential range (EL-EH) to obtain a high leaching efficiency. Moreover, the addition of Cu2 + and Fe2 + accelerated the dissolution of chalcopyrite remarkably at the initial stage of bioleaching, but the further dissolution was inhibited owing to the jarosite formed during the bioleaching process. Therefore, Cu2 + and Fe2 + should be added periodically to prevent the rapid formation of jarosite and enhance the bioleaching efficiency. © 2014 Elsevier B.V. Source


Zhang Y.,Central South University | Zhang Y.,Key Laboratory of Biohydrometallurgy of Ministry of Education | Zhang Y.,University of Alberta | Yang Y.,Central South University | And 4 more authors.
Hydrometallurgy | Year: 2013

A novel Acidithiobacillus ferrooxidans strain QXS-1 was isolated from the acid mine drainage of Qixiashan Pb-Zn-Ag mine area in China. The isolate QXS-1 is a motile, rod-shaped Gram-negative bacterium with an optimum growth at 30 C and pH 2.0. The phylogenetic analysis has demonstrated that QXS-1 is a new strain of A. ferrooxidans. The strain QXS-1 exhibited an unusual trait on the utilization of ferrous iron and sulfur as energy sources. The sulfur-domesticated QXS-1 cells only utilized sulfur as energy source for growth when both ferrous iron and sulfur are available, whereas ferrous-domesticated QXS-1 cells prefer to simultaneously utilize both ferrous iron and sulfur as energy source for growth in the presence of both substrates. The QXS-1 cells accumulated intracellular hydrophilic sulfur during growth. Based on the ultrastructure study, we deduced that the accumulated sulfur in QXS-1 exists in both octasulfur ring form and polysulfide form. The strain QXS-1 exhibited remarkable marmatite-bioleaching capacity. It is able to extract 6585 mg/L zinc from marmatite within 18 days in shake flask. © 2013 Elsevier B.V. All rights reserved. Source


Wang J.,Central South University | Wang J.,Key Laboratory of Biohydrometallurgy of Ministry of Education | Tao L.,Central South University | Tao L.,Key Laboratory of Biohydrometallurgy of Ministry of Education | And 19 more authors.
Minerals Engineering | Year: 2016

The cooperative interactions between chalcopyrite and bornite during bioleaching by mixed moderately thermophilic culture were investigated mainly by bioleaching experiments and electrochemical experiments. Bioleaching results showed that a cooperative effect existed between chalcopyrite and bornite. When the mass ratio of chalcopyrite to bornite was 3:1, an extremely high copper extraction of more than 88% was achieved after bioleaching for 27 days. One of the major reasons for the cooperative effect was that a certain redox potential range (370-450 mV vs. Ag/AgCl) could be maintained for a long period of time during bioleaching due to the mixture of chalcopyrite and bornite. Electrochemical measurements revealed that chalcopyrite was much easier to be reduced than oxidized, while bornite was prone to be directly oxidized. Hence, galvanic effect between chalcopyrite and bornite enhanced the reduction of chalcopyrite to secondary copper-iron species and promoted the oxidative dissolution of bornite. Therefore, redox potential controlling and galvanic effect both contributed to the cooperative bioleaching of chalcopyrite and bornite. © 2016 Published by Elsevier Ltd. Source


Zhao H.,Central South University | Zhao H.,Key Laboratory of Biohydrometallurgy of Ministry of Education | Wang J.,Central South University | Wang J.,Key Laboratory of Biohydrometallurgy of Ministry of Education | And 6 more authors.
International Journal of Electrochemical Science | Year: 2015

In this work, a new stirred reactor was designed and then a comparative study of bioleaching using stirred reactor and shake flask was carried out to investigate the bioleaching performance of the new stirred reactor. Results showed that variations of redox potentials and acid consumptions during were similar in the two systems, and about 15% more copper extraction can be obtained by stirred reactor. Bacterial concentration increased more sharply in the initial stage of bioleaching in stirred reactor. Analytical results showed that a worse passivation caused by larger amount of jarosite and elemental sulfur on the minerals surface leaded the lower copper extraction in shake flask. Electrochemical analysis revealed that the conductivity of bioleaching residues of shake flasks is lower than that of bioleaching residues of stirred reactor. Stirred reactor possesses significant advantages over shake flask in bioleaching of chalcopyrite concentrates can be caused mainly by better mass transfer effect, better air inflation effect and stronger shear force. Therefore, the stirred reactor can be used for both enlarge cultivation of bacteria and tank bioleaching of ores. Electrochemical measurements revealed that chalcopyrite dissolution was preferred to be a continuous reduction-oxidation pathway, in which chalcopyrite was initially reduced and then oxidized, and the initial reduction reaction was the rate-limiting step. © 2015 The Authors. Source


Wang J.,Key Laboratory of Biohydrometallurgy of Ministry of Education | Wang J.,Central South University | Zhao H.,Key Laboratory of Biohydrometallurgy of Ministry of Education | Zhao H.,Central South University | And 6 more authors.
International Journal of Electrochemical Science | Year: 2013

In this work, a comparative study on the electrochemical behavior of massive chalcopyrite electrode in different leaching mediums was carried out to investigate the different interface reactions. The results showed that the dissolution process of chalcopyrite in sulfuric acid solution system involves series of complex oxidation and reduction reactions, containing several intermediate species. The corresponding interface reactions were discussed in details according to some other researches. The results also revealed that the pH values, the addition of Acidithiobacillus ferrooxidans (A.f) and Acidithiobacillus caldus (A.c) do not change the interface reactions of chalcopyrite dissolution. But a lower pH value and the presence of the two strains of bacteria could significantly accelerate the oxidation rate of chalcopyrite. Additionally, low pH value and the presence of Acidithiobacillus ferrooxidans (A.f) made chalcopyrite prone to be reduced to bornite or talnakhite, thus resulting in a higher copper leaching rate. © 2013 by ESG. Source

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