Improved Chalcopyrite Leaching Through Optimization of Redox Potential

Hiroyoshi, Naoki; Tsunekawa, Masami; Okamoto, Hideyuki; Nakayama, Ryoichi; Kuroiwa, Shigeto

doi:10.1179/000844308794408344

Cited by 5 publications

(11 citation statements)

References 6 publications

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“…From previous chemical leaching studies, experimental conditions such as metal ion concentrations, solid/liquid ratios and co-existing minerals were shown to affect the optimal Eh value for Cu extraction (Okamoto 2004(Okamoto , 2005Hiroyoshi 2008aHiroyoshi , 2008b. This could cause misleading interpretation of results obtained from different studies conducted under different conditions.…”

Section: Fe-oxidizersmentioning

confidence: 99%

Microbiological Redox Potential Control to Improve the Efficiency of Chalcopyrite Bioleaching

Masaki

Hirajima

Sasaki

et al. 2018

Geomicrobiology Journal

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The effect of controlling the redox potential (Eh) on chalcopyrite bioleaching kinetics was studied as a new aspect of redox control during chalcopyrite bioleaching, and its mechanism was investigated by employing the "normalized" solution redox potential (Enormal) and the reaction kinetics model. Different Eh ranges were established by use of different acidophiles (Sulfobacillus acidophilus YTF1; Sulfobacillus sibiricus N1; Acidimicrobium ferrooxidans ICP; Acidiplasma sp. Fv-AP). Cu dissolution was very susceptible to real-time change in Eh during the reaction. It was found that efficiency of bioleaching of chalcopyrite can be effectively evaluated on the basis of Enormal, since it is normalized for real-time fluctuations of concentrations of major metal solutes during bioleaching. For steady Cu solubilization during bioleaching at a maximum rate, it was important to maintain a redox potential range of 0 ≤ Enormal ≤ 1 (-0.35 mV optimal) at the mineral surface by employing a "weak" ion-oxidizer. This led to a copper recovery of > 75%. At higher Enormal levels (Enormal > 1 by "strong" microbial Fe 2+ oxidation), Cu solubilization was slowed by diffusion through the product film at the mineral surface (< 50% Cu recovery) caused by low reactivity of the chalcopyrite and by secondary passivation of the chalcopyrite surface, mainly by jarosite.

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Section: Fe-oxidizersmentioning

confidence: 99%

Microbiological Redox Potential Control to Improve the Efficiency of Chalcopyrite Bioleaching

Masaki

Hirajima

Sasaki

et al. 2018

Geomicrobiology Journal

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“…Control of the redox potential of the Fe 3+ /Fe 2+ pair can minimize the formation of iron precipitates, mainly by keeping the Fe 3+ /Fe 2+ ratio low (Córdoba et al, 2008;Hiroyoshi et al, 2008a;Qin et al, 2013). There are many ways of controlling the potential, using the supply of oxygen (Third et al, 2002), addition of sodium sulfite (Sandström et al, 2005), use of chalcopyrite with a higher percentage of pyrite (FeS 2 ) (Hiroyoshi et al, 2008b), and imposition of potential by means of electrochemical techniques such as potentiostatic reduction (Nava et al, 2008), potential pulses (Lara et al, 2013), and cyclic voltammetry (Qin et al, 2013). Depending on the potential range imposed, different phases are formed on the surface, including bornite, covellite, elemental sulfur, non-stoichiometric copper compounds, and chalcocite (Ahmadi et al, 2011;Gu et al, 2013;Lara et al, 2013;Majuste et al, 2012;Nava et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Simulating the main stages of chalcopyrite leaching and bioleaching in ferrous ions solution: An electrochemical impedance study with a modified carbon paste electrode

Arena

Suegama

Bevilaqua

et al. 2016

Minerals Engineering

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In this work, we present an electrochemical study using a carbon paste electrode modified with chalcopyrite (CuFeS 2) in solution A of T&K medium with different ferrous ion concentrations, in the absence and presence of the bacterium Acidithiobacillus ferrooxidans. The aim was to evaluate the influence of ferrous ions and bacteria on the electrochemical behavior of chalcopyrite. Electrochemical impedance spectroscopy (EIS) was used to investigate the processes occurring at the electrode/solution interface in the different systems, considering the charge transfer reactions involving chalcopyrite and ferrous ions, the presence of a multicomponent layer, and diffusion. The main changes in the chalcopyrite response occurred before 67 h or 43 h of immersion, in the absence or presence of ferrous ions, respectively, indicating that the surface oxide layer present on chalcopyrite was dissolved faster in the presence of ferrous ions. The addition of bacteria decreased the charge transfer reaction resistance, especially when ferrous ions were present. In the presence of Fe 2+ , sulfur and jarosite were detected in the solid residues after leaching, while only jarosite was detected in the bioleaching experiment. The results suggested that ferrous ions accelerated the dissolution of chalcopyrite, and that overlayers including biofilms did not halt chalcopyrite dissolution, indicating that there was no passivation.

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“…Several authors have described the positive effect of both redox potential and ferrous ions on chalcopyrite dissolution, however attributing different significance of each one 7,9,10,21,24,25,26 . For instance, Third et al 21 considered the redox potential a parameter more significant to determine chalcopyrite leaching rates than bacterial cell number or their activity.…”

Section: Leaching Experimentsmentioning

confidence: 99%

“…One of the solutions discussed to overcome this issue considers the control of redox potential throughout (bio)leaching processes that could be achieved either electrochemically by applying a redox potential from an external source through a working electrode or chemically by the addition of reducing and oxidizing agents 7 . The maintenance of the redox potential in a narrow range is discussed by Hiroyoshi and colleagues 9,10 .…”

Section: Introductionmentioning

confidence: 99%

Effect of redox potential on chalcopyrite dissolution imposed by addition of ferrous ions

et al. 2017

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ABSTRACT:Copper is one of the metals with great economic interest and about 70% of it is found in nature as chalcopyrite mineral (CuFeS 2 ). Due to its slow dissolution kinetics, chalcopyrite dissolution is still a challenge for industries and researchers. Control of redox potential though has been said to be the key for increasing dissolution rate in chalcopyrite leaching systems. The current work investigated the effect of redox potential by ferrous ions addition on chalcopyrite (bio)leaching experiments. In abiotic systems, 90% of copper was leached into solution when redox potential was kept low (around 420 mV/Ag/AgCl) whereas in bacterial systems (610 mV/Ag/AgCl) low copper dissolution was observed. SEM analysis suggested presence of new phases that were confirmed by XRD to be elemental sulfur and jarosites and a significant decrease of chalcopyrite peak heights in these analyses was also observed. Jarosite was the only new phase detected in bacterial systems. Passivation of chalcopyrite surface did not occur in either conditions. The results clearly show that low redox potential along with presence of ferrous ions has positively influenced copper recovery, confirming the existence of a critical redox potential range where chalcopyrite dissolution is favored.

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Improved Chalcopyrite Leaching Through Optimization of Redox Potential

Cited by 5 publications

References 6 publications

Microbiological Redox Potential Control to Improve the Efficiency of Chalcopyrite Bioleaching

Microbiological Redox Potential Control to Improve the Efficiency of Chalcopyrite Bioleaching

Simulating the main stages of chalcopyrite leaching and bioleaching in ferrous ions solution: An electrochemical impedance study with a modified carbon paste electrode

Effect of redox potential on chalcopyrite dissolution imposed by addition of ferrous ions

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