Presence Of Iron-oxidizing Bacteria Research Articles

Study of Microbially Influenced Corrosion in the Presence of Iron-Oxidizing Bacteria (Strain DASEWM2)

The present study deals with the investigation of microbially influenced corrosion of mild steel by the iron-oxidizing bacterium (IOB), Pseudomonas sp. strain DASEWM2, using electrochemical tests, immersion tests, and surface analysis. The corrosion rate obtained by Tafel plots was higher after exposure of ~ 24 h to 72 h when the concentration of sessile cells and constituents of extracellular polymeric substances were high. In inoculated media, cyclic polarization curves show lower pitting potential, repassivation potential, and large area under the hysteresis loop, indicating higher susceptibility of steel to localized corrosion. Immersion tests show higher corrosion rate (0.252 ± 0.05 mpy) and large deep pits in the open area (maximum pit depth 140 ± 8 µm) and under crevice (maximum pit depth 95 ± 4 µm) indicating a higher degree of corrosion in inoculated media. Corrosion products formed on corroded steel samples were analyzed using EDAX, XRD, and FTIR techniques. Goethite and lepidocrocite are the main corrosion products in the case of inoculated media. In contrast, lepidocrocite and iron hydrogen phosphate are the main corrosion products in the case of control media. The absence of iron hydrogen phosphate, a protective type of corrosion product, on steel exposed to inoculated media may be responsible for observing a higher degree of corrosion due to bacteria.

Corrosion inhibition of carbon steel in CO2-containing oilfield produced water in the presence of iron-oxidizing bacteria and inhibitors

Inhibition effect of an imidazoline derivative, dodecanoic acid and dodecylamine against CO2 corrosion and microbiologically influence corrosion in a CO2-containing oilfield produced water was studied using surface analysis, weight loss and electrochemical measurements. Results indicated that dodecanoic acid could inhibit the adhesion of iron-oxidizing bacteria (IOB) significantly on carbon steel coupons, but had no effect on the planktonic IOB growth. Its inhibition efficiency reached 88.2% after 43 days of incubation. An imidazoline derivative was found to inhibit the adhesion of IOB on the steel surface, and contributed to lower inhibition effect.

Corrosion Behaviors of Carbon Steel in the Presence of Iron Oxidizing Bacteria Cultured in Reclaimed Water

The corrosion behaviors of carbon steel in the presence of iron oxidizingbacteria (IOB) in reclaimed water was investigated mainly using the static hanging piecemethod, electrochemical analysis, SEM, EDAX, FT-IR and XRD. The results showedthat IOB accelerated the corrosion of carbon steel by 50–100% by attaching to its surface;the corrosion potential of the system with IOB was higher (23–36% negative) thanthat without IOB; bacteria grew (biofilm formed) on the surface of carbon steel and pittingcorrosion occurred on the coupons in the reclaimed water inoculated with IOB, whileno pitting corrosion occurred in the system without IOB. The corrosion products mainlyconsisted of FeOOH and CaCO3 whether IOB existed or not but were more complicatedin the presence of IOB.

황철석과 토착미생물이 광미를 활용한 전기 생산에 미치는 영향

Acid mine drainage (AMD) producing mine tailings can be beneficially recycled to generate electricity by applying fuel cell technology. Pyrite-containing mine tailings and indigenous bacteria from abandoned mine areas were used to construct fuel cells to investigate the effect of pyrite contents and the presence of iron-oxidizing bacteria. The results showed an enhanced electrical performance with a higher content of pyrite in mine tailings. The inoculation of the indigenous bacteria also enhanced the current density by about three times, and the power density by about 10 times. Overall, this study shows that the combined use of the ecological function of indigenous bacteria from mine areas and mine-tailings in fuel cells does not only contribute to reducing harmful effects of mine tailings but also generate electricity.

IMPROVED CHALCOPYRITE LEACHING THROUGH OPTIMIZATION OF REDOX POTENTIAL

In the leaching of chalcopyrite with sulphuric acid solutions, the copper extraction rate reaches a maximum at a given redox potential. This article reviews our studies on the determination of the optimum redox potential for chalcopyrite leaching. Shaking flask and column leaching experiments for a chalcopyrite concentrate were performed under various conditions and the results were analyzed using a normalized redox potential defined from a reaction model assuming the formation of an intermediate Cu2S from chalcopyrite. Factors, such as metal ion concentrations, solid/liquid ratio and the presence of iron-oxidizing bacteria, caused significant variations in the copper extraction versus time plots. However the copper extraction rate versus normalized redox potential plots were independent of the above factors and the copper extraction rate reached a maximum at the normalized redox potentials around 0.43. Converting the normalized redox potential to the solution redox potential gives the optimum redox potential for chalcopyrite leaching as a function of cupric and ferrous ion concentrations. This semi-empirical equation can be used to predict the optimum redox potential during leaching operation and is useful to design the redox-controlled heap leaching for chalcopyrite. Lors de la lixiviation de la chalcopyrite avec des solutions d’acide sulfurique, la vitesse d’extraction du cuivre atteint un maximum à un potentiel rédox donné. Cet article examine notre étude de la détermination du potentiel rédox optimal de lixiviation de la chalcopyrite. On a effectué, sous diverses conditions, des expériences d’agitation du flacon et de lixiviation en colonne d’un concentré de chalcopyrite et l’on a analysé les résultats en utilisant un potentiel rédox normalisé défini à partir d’un modèle de réaction assumant la formation d’une forme active intermédiaire Cu2S à partir de la chalcopyrite. Des facteurs, comme les concentrations de l’ion métal, le rapport solide/liquide et la présence de bactéries oxydantes du fer, avaient pour conséquence des variations importantes dans l’extraction du cuivre par rapport au temps. Cependant, la vitesse d’extraction du cuivre par rapport aux graphes du potentiel rédox normalisé était indépendante des facteurs ci-dessus et elle atteignait un maximum aux potentiels rédox normalisés autour de 0.43. La conversion du potentiel rédox normalisé en potentiel rédox de la solution donne le potentiel rédox optimal pour la lixiviation de la chalcopyrite en fonction de la concentration des ions cuivriques et ferreux. On peut utiliser cette équation semiempirique pour prédire le potentiel rédox optimal lors de l’opération de lixiviation et cette dernière est utile pour concevoir la lixiviation en tas de la chalcopyrite contrôlée par le rédox.

Localized corrosion behavior of 316L stainless steel in the presence of sulfate-reducing and iron-oxidizing bacteria

Localized corrosion behavior of 316L stainless steel was investigated in the presence of sulfate-reducing bacteria (SRB) and iron-oxidizing bacteria (IOB) isolated from cooling water system using polarization measurement, scanning electron microscopy (SEM) examinations and energy dispersive spectrum (EDS) analysis. The results show the corrosion potential ( E corr) and breakdown potential ( E b) of SS decreased in turn with the presence of IOB, SRB and SRB + IOB, indicating decreased relative resistance to localized corrosion. E corr in the sterile medium remained virtually unchanged with exposure time, indicating that localized attack did not occur. However, micrometer-scale pitting was observed on the SS surface in the presence of bacteria. The presence of SRB demonstrated higher corrosion rates than IOB. The combination of SRB and IOB yielded the highest corrosion rate. The presence and metabolic activities of bacteria on SS surface produce environments that can alter rates of partial reactions in corrosion processes and shift corrosion mechanisms. The most severe microbiologically induced corrosion takes place in aquatic solution where physiological groups of aerobic and anaerobic microorganisms interact.

Corrosion of Low Carbon Steel Influenced by the Presence of Iron-oxidizing Bacteria (Leptothrix discophora)

Corrosion of Low Carbon Steel Influenced by the Presence of Iron-oxidizing Bacteria (Leptothrix discophora)

Kinetic model for simultaneous leaching of zinc sulfide and manganese dioxide in the presence of iron-oxidizing bacteria

The effect of iron-oxidizing bacteria on the simultaneous leaching of zinc sulfide and manganese dioxide was studied. Some researchers have reported the enhancement of the leaching rate during the simultaneous leaching of metal oxides and metal sulfides. In the present study, we examined the effect of the presence of Thiobacillus ferrooxidans in the simultaneous leaching. We also examined the reaction rates during the simultaneous leaching in the presence of the bacteria in order to study the reaction kinetics. The rate equation was obtained for each reaction: the oxidation of zinc sulfide by ferric iron, the oxidation of zinc sulfide by ferric iron and by the bacteria, the reductive dissolution of manganese dioxide by ferrous iron, and the simultaneous dissolution of zinc sulfide and manganese dioxide. A kinetic model based on these equations was proposed and the extent of leaching during the simultaneous dissolution with T. ferrooxidans was determined.