Leaching of Zinc Sulfide by Thiobacillus ferrooxidans: Experiments with a Controlled Redox Potential Indicate No Direct Bacterial Mechanism

1998 ◽  
Vol 64 (10) ◽  
pp. 3570-3575 ◽  
Author(s):  
T. A. Fowler ◽  
F. K. Crundwell
Keyword(s):  
Redox Potential ◽  
Zinc Sulfide ◽  
Thiobacillus Ferrooxidans ◽  
Experimental Period ◽  
Electrolytic Cell ◽  
Ferric Ions ◽  
Ferrous Ions ◽  
Bacterial Leaching ◽  
Dissolved Iron

ABSTRACT The role of Thiobacillus ferrooxidans in bacterial leaching of mineral sulfides is controversial. Much of the controversy is due to the fact that the solution conditions, especially the concentrations of ferric and ferrous ions, change during experiments. The role of the bacteria would be more easily discernible if the concentrations of ferric and ferrous ions were maintained at set values throughout the experimental period. In this paper we report results obtained by using the constant redox potential apparatus described previously (P. I. Harvey and F. K. Crundwell, Appl. Environ. Microbiol. 63:2586–2592, 1997). This apparatus is designed to control the redox potential in the leaching compartment of an electrolytic cell by reduction or oxidation of dissolved iron. By controlling the redox potential the apparatus maintains the concentrations of ferrous and ferric ions at their initial values. Experiments were conducted in the presence of T. ferrooxidans and under sterile conditions. Analysis of the conversion of zinc sulfide in the absence of the bacteria and analysis of the conversion of zinc sulfate in the presence of the bacteria produced the same results. This indicates that the only role of the bacteria under the conditions used is regeneration of ferric ions in solution. In this work we found no evidence that there is a direct mechanism for bacterial leaching.

Mechanism of Pyrite Dissolution in the Presence ofThiobacillus ferrooxidans

1999 ◽  
Vol 65 (7) ◽  
pp. 2987-2993 ◽  
Author(s):  
T. A. Fowler ◽  
P. R. Holmes ◽  
F. K. Crundwell
Keyword(s):  
Redox Potential ◽  
Thiobacillus Ferrooxidans ◽  
Ferric Ions ◽  
Ferrous Ions ◽  
Bacterial Leaching ◽  
Experimental Conditions ◽  
Appl Environ ◽  
Sulfate Solutions ◽  
Rate Of Dissolution ◽  
Experimental Apparatus

ABSTRACT In spite of the environmental and commercial interests in the bacterial leaching of pyrite, two central questions have not been answered after more than 35 years of research: does Thiobacillus ferrooxidans enhance the rate of leaching above that achieved by ferric sulfate solutions under the same conditions, and if so, how do the bacteria affect such an enhancement? Experimental conditions of previous studies were such that the concentrations of ferric and ferrous ions changed substantially throughout the course of the experiments. This has made it difficult to interpret the data obtained from these previous works. The aim of this work was to answer these two questions by employing an experimental apparatus designed to maintain the concentrations in solution at a constant value. This was achieved by using the constant redox potential apparatus described previously (P. I. Harvey, and F. K. Crundwell, Appl. Environ. Microbiol. 63:2586–2592, 1997; T. A. Fowler, and F. K. Crundwell, Appl. Environ. Microbiol. 64:3570–3575, 1998). Experiments were conducted in both the presence and absence of T. ferrooxidans, maintaining the same conditions in solution. The rate of dissolution of pyrite with bacteria was higher than that without bacteria at the same concentrations of ferrous and ferric ions in solution. Analysis of the dependence of the rate of leaching on the concentration of ferric ions and on the pH, together with results obtained from electrochemical measurements, provided clear evidence that the higher rate of leaching with bacteria is due to the bacteria increasing the pH at the surface of the pyrite.

Optimal conditions for bio-oxidation of ferrous ions to ferric ions using Thiobacillus ferrooxidans

2002 ◽  
Vol 85 (3) ◽  
pp. 225-234 ◽  
Author(s):  
S Malhotra ◽  
A.S Tankhiwale ◽  
A.S Rajvaidya ◽  
R.A Pandey
Keyword(s):  
Thiobacillus Ferrooxidans ◽  
Optimal Conditions ◽  
Ferric Ions ◽  
Ferrous Ions

scholarly journals Role of Ferrous Ions in Synthetic Cobaltous Sulfide Leaching of Thiobacillus ferrooxidans

1984 ◽  
Vol 48 (3) ◽  
pp. 461-467 ◽  
Author(s):  
Tsuyoshi Sugio ◽  
Chitoshi Domatsu ◽  
Tatsuo Tano ◽  
Kazutami Imai
Keyword(s):  
Thiobacillus Ferrooxidans ◽  
Ferrous Ions

Leaching of Zinc Sulfide by Thiobacillus ferrooxidans: Bacterial Oxidation of the Sulfur Product Layer Increases the Rate of Zinc Sulfide Dissolution at High Concentrations of Ferrous Ions

1999 ◽  
Vol 65 (12) ◽  
pp. 5285-5292 ◽  
Author(s):  
T. A. Fowler ◽  
F. K. Crundwell
Keyword(s):  
Zinc Sulfide ◽  
Thiobacillus Ferrooxidans ◽  
Particle Surface ◽  
Product Layer ◽  
Ferrous Ions ◽  
Bacterial Oxidation ◽  
Rate Of Dissolution ◽  
Shrinking Core ◽  
Leaching Experiments ◽  
High Concentrations

ABSTRACT This paper reports the results of leaching experiments conducted with and without Thiobacillus ferrooxidans at the same conditions in solution. The extent of leaching of ZnS with bacteria is significantly higher than that without bacteria at high concentrations of ferrous ions. A porous layer of elemental sulfur is present on the surfaces of the chemically leached particles, while no sulfur is present on the surfaces of the bacterially leached particles. The analysis of the data using the shrinking-core model shows that the chemical leaching of ZnS is limited by the diffusion of ferrous ions through the sulfur product layer at high concentrations of ferrous ions. The analysis of the data shows that diffusion through the product layer does not limit the rate of dissolution when bacteria are present. This suggests that the action of T. ferrooxidans in oxidizing the sulfur formed on the particle surface is to remove the barrier to diffusion by ferrous ions.

The role of iron in the weathering of a climosequence of soils derived from schist

Soil Research ◽  
1991 ◽  
Vol 29 (3) ◽  
pp. 387 ◽  
Author(s):  
LP Aldridge ◽  
GJ Churchman
Keyword(s):  
New Zealand ◽  
Mössbauer Spectra ◽  
Ferric Ions ◽  
Ferrous Ions ◽  
Rock Samples ◽  
Mossbauer Spectra ◽  
Muscovite Mica ◽  
Primary Minerals ◽  
Close Parallel

Mossbauer spectra were obtained of the whole soil and clay fractions and some of the sand fractions, as well as some rock samples that were taken from eight soils forming a climosequence on schist in South Island, New Zealand. They show that the main changes in iron across the sequence involve the oxidation of ferrous ions in muscovite mica and its initial weathering products to ferric ions in these minerals and also in oxyhydroxides. The extremes of weathering in the sequence led to the mobilization of iron from primary minerals in soils at the surface of profiles into oxyhydroxides that were deposited lower down in these profiles. While these changes in iron have occurred alongside the loss of K+ from the interlayers of the micas to form expanded phases, there is not a close parallel between the changes on oxidation and those from the initial loss of interlayer potassium.

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

2017 ◽  
Vol 42 (1) ◽  
pp. 40 ◽  
Author(s):  
Ana Laura Araújo Santos ◽  
Fabiana Antonia Arena ◽  
Assis Vicente Benedetti ◽  
Denise Bevilaqua
Keyword(s):  
Redox Potential ◽  
Acid Leaching ◽  
Dissolution Kinetics ◽  
Sem Analysis ◽  
Conclusive Evidence ◽  
Copper Recovery ◽  
Potential Range ◽  
Ferrous Ions ◽  
Copper Dissolution

Copper is a metal with a great economic interest and about 70% is found in nature in chalcopyrite form (CuFeS2). However the chalcopyrite dissolution is a challenge for industries as well as researchers because of its slow dissolution kinetics. The control of redox potential is one factor that can help in this drawback. This study was undertaken to evaluate the role of redox potential on chalcopyrite bioleaching by addition of ferrous ions. Acid leaching with addition of ferrous ions promoted high dissolution of chalcopyrite by the maintenance of low redox potential (420 mV/Ag/AgCl). On the other hand, the copper dissolution in bacterial systems showed low copper recovery (610 mV/Ag/AgCl). XRD of solid residues showed in abiotic conditions the formation of elemental sulfur, jarosites and a significant decrease on chalcopyrite’s peaks. In bacterial conditions, only jarosites was detected as new crystalline phase. SEM analysis confirmed the results obtained by XRD. In general, the results showed conclusive evidence that the maintenance of low redox potential and the addition of ferrous ions have positively influenced the copper recovery and confirmed the literature data, which indicate a critical potential range where chalcopyrite leaching is more favorable.

scholarly journals In situ synthesis of methane using Ag–GDC composite electrodes in a tubular solid oxide electrolytic cell: new insight into the role of oxide ion removal

2021 ◽  
Vol 5 (7) ◽  
pp. 2055-2064
Author(s):  
Saheli Biswas ◽  
Aniruddha P. Kulkarni ◽  
Daniel Fini ◽  
Sarbjit Giddey ◽  
Sankar Bhattacharya
Keyword(s):  
Electrolytic Cell ◽  
Composite Electrodes ◽  
Ion Removal ◽  
Single Temperature ◽  
Methanation Catalyst ◽  
Oxide Ion ◽  
Insight Into ◽  
Electrochemical Phenomenon

In situ synthesis of methane in a single-temperature zone SOEC in the absence of any methanation catalyst is a completely electrochemical phenomenon governed by the thermodynamic equilibrium of various reactions.

scholarly journals Role of redox-inactive metals in controlling the redox potential of heterometallic manganese–oxido clusters

2021 ◽  
Author(s):  
Keisuke Saito ◽  
Minesato Nakagawa ◽  
Manoj Mandal ◽  
Hiroshi Ishikita
Keyword(s):  
Photosystem Ii ◽  
Redox Potential ◽  
Quantum Chemical Calculations ◽  
Catalytic Reaction ◽  
Quantum Chemical ◽  
Ionic Radius ◽  
Redox Potentials ◽  
Oxygen Evolving ◽  
Highest Occupied Molecular Orbitals

AbstractPhotosystem II (PSII) contains Ca2+, which is essential to the oxygen-evolving activity of the catalytic Mn4CaO5 complex. Replacement of Ca2+ with other redox-inactive metals results in a loss/decrease of oxygen-evolving activity. To investigate the role of Ca2+ in this catalytic reaction, we investigate artificial Mn3[M]O2 clusters redox-inactive metals  [M] ([M]  = Mg2+, Ca2+, Zn2+, Sr2+, and Y3+), which were synthesized by Tsui et al. (Nat Chem 5:293, 2013). The experimentally measured redox potentials (Em) of these clusters are best described by the energy of their highest occupied molecular orbitals. Quantum chemical calculations showed that the valence of metals predominantly affects Em(MnIII/IV), whereas the ionic radius of metals affects Em(MnIII/IV) only slightly.

Quinone-enhanced Ascorbate Reduction of Nitric Oxide: Role of Quinone Redox Potential

2004 ◽  
Vol 38 (10) ◽  
pp. 1107-1112 ◽  
Author(s):  
Antonio E. Alegria ◽  
Sheila Sanchez ◽  
Ingrid Quintana
Keyword(s):  
Nitric Oxide ◽  
Redox Potential
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