Investigating the Bioleaching of an Arsenic Mine Tailing Using a Mixed Mesophilic Culture

2017 ◽  
Vol 262 ◽  
pp. 668-672 ◽  
Author(s):  
Emmanuel Ngoma ◽  
Kathija Shaik ◽  
Danilo Borja ◽  
Mariette Smart ◽  
Jay Hyun Park ◽  
...  
Keyword(s):  
Iron Oxidation ◽  
Column Experiment ◽  
Packed Bed ◽  
Microbial Colonization ◽  
Post Inoculation ◽  
Initial Inoculum ◽  
South Korean ◽  
Oxidation Rates ◽  
C 30 ◽  
Kinetics Of

The aim of this study was to investigate the microbial colonization and arsenic leaching kinetics of South Korean mine tailings containing arsenopyrite at fixed temperatures (20°C, 30°C and 45°C) and at ramped up temperatures (25 to 45°C, with a 2°C daily increase). The experiments were conducted in a packed bed of inert granite pebbles coated with the tailings material and leached with a mesophilic culture dominated by Acidithiobacillus caldus (56%), a lesser percentage of Leptospirillum ferriphilum (29%) and Archaea (15%), using 1 g/L ferrous-enriched 0K medium. The ramped-up temperature experiment was conducted in triplicate and columns were sacrificed after different leach periods to study the evolution of microbial species dominating the colonization. The leaching performance was evaluated using the arsenic released into solution, the iron oxidation rates, the pH and the redox potential. The microbial speciation of the culture attached to the solids during the leach experiment was determined upon completion of each experiment. A steady arsenic solubilisation of between 94 and 97% was observed among the various column experiment after 88 days post inoculation. Microbial speciation performed following the leaching of the mineral indicated a shift of microbial communities in the columns when compared to the initial inoculum.

A Novel Apparatus to Determine the Bio-Oxidation Kinetics of Sessile Leptospirillum ferriphilum

2013 ◽  
Vol 825 ◽  
pp. 238-241 ◽  
Author(s):  
Porogo Duku ◽  
Sanet H. Minnaar ◽  
Susan T.L. Harrison ◽  
Jochen Petersen
Keyword(s):  
Oxidation Kinetics ◽  
Iron Oxidation ◽  
Packed Bed ◽  
Leptospirillum Ferriphilum ◽  
Oxidation Rates ◽  
Cell Counts ◽  
Ferrous Iron Oxidation ◽  
Uptake Rates ◽  
Carbon Utilisation ◽  
Kinetics Of

A novel apparatus was developed to test the ferrous iron oxidation kinetics of Leptospirillum ferriphilum in predominantly sessile culture, by combining a CSTR under wash-out conditions with a packed bed of inert ceramic saddles. Results indicate that a dense culture of sessile bacteria is established rapidly, which achieves high oxidation rates in all experiments with a yield in terms of CO2 uptake rates comparable or higher to what has been measured in planktonic culture. However, the yield in terms of cell counts changes dramatically, indicating a substantial shift in carbon utilisation in the sessile culture. The apparatus is feasible as a method to study iron oxidation kinetics of sessile cultures, providing it is operated at sufficiently high recycle ratios.

Temperature Effects on the Iron Oxidation Kinetics of a Leptospirillum ferriphilum Dominated Culture at pH Below One

2007 ◽  
Vol 20-21 ◽  
pp. 465-468 ◽  
Author(s):  
Bestamin Özkaya ◽  
Pauliina Nurmi ◽  
Erkan Sahinkaya ◽  
Anna H. Kaksonen ◽  
Jaakko A. Puhakka
Keyword(s):  
Ferric Iron ◽  
Arrhenius Equation ◽  
Iron Oxidation ◽  
Iron Concentration ◽  
Leptospirillum Ferriphilum ◽  
Temperature Range ◽  
Oxidation Rates ◽  
Ferrous Iron Oxidation ◽  
Maximum Temperatures ◽  
Kinetics Of

In this study, ferrous iron oxidation rates of a Leptospirillum ferriphilum dominated culture were determined over the temperature range of 2-50oC at pH below one. The results show that at pH 0.9 the culture oxidizes iron within the temperature range of 10°C to 45°C. Using the Arrhenius equation, an Ea value of 89.9 ± 6.75 kJ/mol was calculated. From the data fitted to Ratkowsky Equation, the optimum, minimum and maximum temperatures were 35 ± 1.5, 9.96 ± 1.72 and 42.93 ± 0.64 °C for this culture, respectively. The redox potential of the solution becomes more positive, which was the maximum (650-700 mV) at temperatures between 19-40 oC due to completing biological oxidation and increasing in ferric iron concentration.

Ferrous Iron Oxidation in Packed-Bed Reactors at Elevated Temperatures

2015 ◽  
Vol 1130 ◽  
pp. 226-229 ◽  
Author(s):  
Aleksander Bulaev
Keyword(s):  
Ferrous Iron ◽  
Elevated Temperatures ◽  
Iron Oxidation ◽  
Packed Bed ◽  
Thermophilic Microorganisms ◽  
Packed Bed Reactors ◽  
Moderately Thermophilic ◽  
Oxidation Rates ◽  
Ferrous Iron Oxidation ◽  
In Series

The ferrous iron oxidation by mixed culture of moderately thermophilic microorganisms (Sulfobacillus thermosulfidooxidansSh 10-1 andAcidiplasmaMBA-1) was investigated in continuous experiments in three packed-bed reactors connected in series at temperature 55°C, and a pH of 1.0. Two solutions were used in the experiments. The first one contained (g L-1) 59 Fe2+, the second one contained (g L-1) 59 Fe2+, 16 Fe3+, 2 Cu2+, 2 Zn2+. The hydraulic retention time was 120 hours. Iron oxidation rates in the experiment with the first solution were 0.5, 0.35, and 0.2 g L-1h-1in first, second and third reactor, respectively. The oxidation rates in the experiment with the second solution were 0.3, 0.2, and 0.185 g L-1h-1in first, second and third reactor, respectively. Iron oxidation efficiencies in the experiments with the first and second solutions were 77% and 47%. Stable continuous iron oxidation at high temperature was successfully demonstrated, but further investigations are required for improving the rate and efficiencies of oxidation.

Biological iron oxidation-reduction and the effects on sulfur oxidation-reduction, denitrification and poly-P accumulation in an anaerobic-oxic activated sludge

2002 ◽  
Vol 46 (1-2) ◽  
pp. 55-60 ◽  
Author(s):  
R. Yamamoto-Ikemoto ◽  
T. Komori ◽  
S. Matsui
Keyword(s):  
Activated Sludge ◽  
Sulfate Reduction ◽  
Iron Reduction ◽  
Iron Oxidation ◽  
Sulfur Oxidation ◽  
Monod Equation ◽  
Oxidation Rates ◽  
Oxidation Reduction ◽  
Initial Iron ◽  
P Accumulation

Iron oxidation and reduction were examined using the activated sludge from a municipal plant. Iron contents of the activated sludge were 1–2%. Iron oxidation rates were correlated with the initial iron concentrations. Iron reducing rates could be described by the Monod equation. The effects of iron reducing bacteria on sulfate reduction, denitrification and poly-P accumulation were examined. Iron reduction suppressed sulfate reduction by competing with hydrogen produced from protein. Denitrification was outcompeted with iron reduction and sulfate reduction. These phenomena could be explained thermodynamically. Poly-P accumulation was also suppressed by denitrification. The activity of iron reduction was relatively high.

scholarly journals Kinetics of iron oxidation-reduction in hydrous silicic melts

2002 ◽  
Vol 87 (7) ◽  
pp. 829-837 ◽  
Author(s):  
Fabrice Gaillard ◽  
Bruno Scaillet ◽  
Michel Pichavant
Keyword(s):  
Iron Oxidation ◽  
Oxidation Reduction ◽  
Kinetics Of

Heat acclimation memory: do the kinetics of the deacclimated transcriptome predispose to rapid reacclimation and cytoprotection?

2014 ◽  
Vol 117 (11) ◽  
pp. 1262-1277 ◽  
Author(s):  
Anna Tetievsky ◽  
Miri Assayag ◽  
Rotem Ben-Hamo ◽  
Sol Efroni ◽  
Gal Cohen ◽  
...  
Keyword(s):  
Heat Acclimation ◽  
Left Ventricular ◽  
Molecular Memory ◽  
Transcriptional Responses ◽  
Linker Histones ◽  
Chromatin Compaction ◽  
Physiological Adaptations ◽  
C 30 ◽  
Kinetics Of ◽  
Mrna Hybridization

Faster reinduction of heat acclimation (AC) after its decline indicates “AC memory.” Our previous results revealed involvement of epigenetic mechanisms of transcriptional regulation. We hypothesized that the decline of AC (DeAC) is a period of “dormant memory” during which many processes are alerted to enable rapid reacclimation (ReAC). Using a genomewide approach we studied the AC, DeAC, and ReAC transcriptomes, to uncover hallmark pathways linked to “molecular memory” in the cardioacclimatome. Fifty rats subjected to heat acclimation [34°C for 2d (AC2d) or 30d (AC30)], DeAC (24°C, 30 days), ReAC (34°C, 2 days), and untreated controls were used. The GeneChip Rat Gene 1.0 ST Array was employed for left ventricular (cardiac) mRNA hybridization. Three independent bioinformatic analyses showed that 1) during AC2d enrichment of DNA impair/repair-linked genes is seen, and this is the molecular on-switch of acclimation; 2) genes activated in AC30 underlie the qualitative physiological adaptations of cardiac performance; 3) particular molecular programs encompassing constitutive upregulation of p38 MAPK, Jak/Stat, and Akt pathways and targets are specifically activated during DeAC and ReAC; and 4) epigenetic markers such as linker histones (histones H1 cluster), associated with nucleosome spacing, transcriptional chromatin modifiers, poly-(ADP-ribose) polymerase-1 (PARP1) linked to chromatin compaction, and microRNAs are only altered during DeAC/ReAC. The latter are newcomers to the AC/DeAC puzzle. We suggest that these transcriptional responses maintain euchromatin and proteostasis and enable faster physiological recovery upon ReAC by rapidly reestablishing the protected acclimated cardiophenotype. We propose that the cardiac AC model can be applied to acclimation processes in general.

scholarly journals Reaction Kinetics of Iron Oxides in Ok Tedi Magnetite Skarn Ore

2020 ◽  
pp. 1-13
Author(s):  
Mary Kama ◽  
Kaul Gena ◽  
Tindi Seje Nuru
Keyword(s):  
Reaction Kinetics ◽  
Papua New Guinea ◽  
Iron Reduction ◽  
New Guinea ◽  
Reaction Rate Constant ◽  
Close Monitoring ◽  
Significant Difference ◽  
Different Temperatures ◽  
C 30 ◽  
Kinetics Of

Magnetic skarn ore (MSO) is one of the major copper bearing ore extracted by the Ok Tedi Copper Mine in Papua New Guinea (PNG). Copper minerals are recovered by flotation while the iron not associated with copper are discarded as tailings. The objective of this investigation was to determine the iron ore reduction kinetics for the Ok Tedi MSO and ascertain if it can be processed to produce sponge iron for a mini steel plant in Papua New Guinea. SEM-EDAX analyses of the Ok Tedi MSO indicated 10.1% C, 30% O, 0.6% Mg, 1.1% Si, 21.1% S, 0.8% Ca and 36.2 % Fe. Most of the iron is in sulfide form. Both naturally occurring and roasted sinters of Ok Tedi MSO samples of different particle sizes were reduced by charcoal carbon at three different temperatures and seven different reduction times. Analyses of the reduced products indicated a metallic iron content of more than 65 wt. % on average. Results showed that there was no significant difference in reduction between fluxed and control materials. Only a slight increase in kinetics with reduced particle size, hence the reaction rate constant (K) did not vary much within the temperatures investigated. Reaction kinetics increases with increasing reduction time at 900°C. Therefore, more iron reduction is observed with particles of 106 µm size. In addition, the results also confirmed that the reduction energy used was higher at 800°C and lower at 1000°C. In conclusion, iron reduction can be improved but close monitoring of temperature and reduction times are essential to determine the reaction kinetics of the Ok Tedi MSO.

scholarly journals A kinetic model of ferrous iron oxidation by Acidithiobacillus ferrooxidans in a batch culture

2005 ◽  
Vol 11 (2) ◽  
pp. 59-62 ◽  
Author(s):  
Dragisa Savic ◽  
Miodrag Lazic ◽  
Vlada Veljkovic ◽  
Miroslav Vrvic
Keyword(s):  
Kinetic Model ◽  
Acidithiobacillus Ferrooxidans ◽  
Ferrous Iron ◽  
Bubble Column ◽  
Iron Oxidation ◽  
Yield Coefficient ◽  
Transfer Rates ◽  
Ferrous Iron Oxidation ◽  
Menten Kinetic ◽  
Kinetics Of

The batch oxidation kinetics of ferrous iron by Acidithiobacillus ferrooxidans were examined at different oxygen transfer rates and pH in an aerated stirred tank and a bubble column. The microbial growth, oxygen consumption rate and ferrous and ferric iron were monitored during the biooxidation. A kinetic model was established on the basis of the Michaelis-Menten kinetic equation for bacterial growth and the constants estimated from experimental data (maximum specific growth rate 0.069 h-1, saturation constant 2.9 g/dm3, and biomass yield coefficient based on ferrous iron 0.003 gd.w./gFe). Values calculated from the model agreed well with the experimental ones regardless of the bioreactor type and pH conditions.

scholarly journals Infectious SARS-CoV-2 is emitted in aerosols

2021 ◽  
Author(s):  
Seth A. Hawks ◽  
Aaron J. Prussin ◽  
Sarah C. Kuchinsky ◽  
Jin Pan ◽  
Linsey C. Marr ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Infectious Virus ◽  
Emission Rate ◽  
Clinical Signs ◽  
Respiratory Viruses ◽  
Post Inoculation ◽  
Viral Shedding ◽  
Contact Transmission ◽  
Respiratory Droplets ◽  
Kinetics Of

Respiratory viruses such as SARS-CoV-2 are transmitted in respiratory droplets and aerosols, which are released during talking, breathing, coughing, and sneezing. Non-contact transmission of SARS-CoV-2 has been demonstrated, suggesting transmission in aerosols. Here we demonstrate that golden Syrian hamsters emit infectious SARS-CoV-2 in aerosols, prior to and concurrent with the onset of mild clinical signs of disease. The emission rate is 25 infectious virions/hour on days 1 and 2 post-inoculation, with viral RNA levels 200-fold higher than infectious virus in aerosols. Female hamsters have delayed kinetics of viral shedding in aerosols compared to male hamsters. The majority of virus is contained within aerosols <8 microns in size. Thus, we provide direct evidence that, in hamsters, SARS-CoV-2 is an airborne virus.

scholarly journals The Cyclic Oxidation and Hardness Characteristics of Thermally Exposed Titanium Prepared by Inductive Sintering-Assisted Powder Metallurgy

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 104
Author(s):  
Fahamsyah H. Latief ◽  
El-Sayed M. Sherif ◽  
Agus S. Wismogroho ◽  
Wahyu B. Widayatno ◽  
Hany S. Abdo
Keyword(s):  
Powder Metallurgy ◽  
Single Phase ◽  
Oxide Scales ◽  
Cyclic Tests ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxidation Rates ◽  
Parabolic Law ◽  
Kinetics Of ◽  
Hardness Values

The oxidation and hardness of thermally exposed titanium (Ti) prepared using inductive sintering-assisted powder metallurgy was evaluated through cyclic tests in air at 700–900 °C for 100 h (5 cycles). In general, the oxidation kinetics of the Ti samples followed the parabolic law and their oxidation rates increased with increasing oxidation temperatures. The rutile form of titanium dioxide (TiO2) was detected by X-ray diffraction in the oxide scales after oxidation at 700 °C and 900 °C. Furthermore, the TiO2 grain size and thickness were significantly influenced by an increase in the oxidation temperature. Lastly, the formation of rutile as a single-phase on the surface of oxidized Ti enhanced the hardness of the oxide scales, whereas the substrate had lower hardness values than the oxide scales due to diffusion of Ti atoms at the surface to form the TiO2 oxide scales.

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