scholarly journals Measurement of Changing Ferrous Iron Concentration Using Redox Potential

1990 ◽  
Vol 13 (4) ◽  
pp. 245-254,226 ◽  
Author(s):  
Setuko KOBAYASHI ◽  
Hajime NISHIMURA
Keyword(s):  
Redox Potential ◽  
Ferrous Iron ◽  
Iron Concentration

Laser-Excited Fluorescence of Dityrosine

1995 ◽  
Vol 49 (11) ◽  
pp. 1669-1676 ◽  
Author(s):  
Sahar F. Mahmoud ◽  
Stephen E. Bialkowski
Keyword(s):  
Ferrous Iron ◽  
Ferric Iron ◽  
Iron Concentration ◽  
Fluorescence Emission ◽  
Fluorescence Yield ◽  
Photomultiplier Tube ◽  
Alkaline Solutions ◽  
Array Detector ◽  
Fluorescence Maximum ◽  
Fluorescence Efficiency

In this research, laser-excited fluorescence was examined for sensitive detection of aqueous dityrosine. Samples were excited with a 6.3-mW, 325-nm helium-cadmium laser focused into a small volume-fluorescence cell with a 10-cm lens. The resulting fluorescence emission was collected perpendicular to the excitation and detected with two different schemes. An optical bandpass filter was used with a photomultiplier tube for sensitive quantitative measurement, while a photodiode array detector was used in conjunction with a spectrograph for qualitative characterization of fluorescence emission spectra. Dityrosine detection on the order of 2 × 10−11 M was obtained with the use of the photomultiplier tube with bandpass optical filter. The dityrosine fluorescence yield is found to vary with the solution pH, the relative concentrations of ferric and ferrous iron, and the amount of dissolved oxygen. A maximum fluorescence yield is observed for iron-free, oxygen-free alkaline solutions. Fluorescence quenching by oxygen is a cumulative photolysis effect that diminished fluorescence yield with increased irradiation time. Flowing the solutions minimized photolysis effects in oxygenated solutions. Quenching by ferrous and ferric iron is found to be due primarily to complex formation. The ferrous iron complex appears to have a fluorescence efficiency of ∼20% of the free dityrosine. The ferric iron dityrosine complex appears to have two ferric ions per molecule at low iron concentration. Other complexes may form at different concentrations. Solvent effects on dityrosine absorption and fluorescence spectra were also investigated. A red shift in dityrosine fluorescence maximum was observed in 1 M trichloroacetic acid and in N, N-dimethylformamide. The fluorescence emission maximum was shifted to the blue in acetonitrile and glacial acetic acid. These shifts were attributed to typical solvochromic behavior.

scholarly journals Electrochemically Induced Metal- vs. Ligand-Based Redox Changes in Mackinawite: Identification of a Fe3+- and Polysulfide-Containing Intermediate

2021 ◽  
Author(s):  
Sebastian Sanden ◽  
Robert Szilagyi ◽  
Yamei Li ◽  
Norio Kitadai ◽  
Samuel M Webb ◽  
...  
Keyword(s):  
Redox Potential ◽  
Ferrous Iron ◽  
Maturation Process ◽  
Anaerobic Conditions ◽  
Ph Dependent

Under anaerobic conditions, ferrous iron reacts with sulfide producing FeS, which can then undergo a temperature, redox potential, and pH dependent maturation process resulting in the formation of oxidized mineral...

The effect of certain biochemical factors on well clogging under suboxic and mildly anoxic conditions

2012 ◽  
Vol 65 (12) ◽  
pp. 2206-2212 ◽  
Author(s):  
M. Dimkić ◽  
M. Pušić ◽  
V. Obradović ◽  
S. Kovačević
Keyword(s):  
Redox Potential ◽  
Hydraulic Resistance ◽  
Iron Concentration ◽  
Research Project ◽  
Anoxic Conditions ◽  
Rate Of Increase ◽  
Well Clogging ◽  
Groundwater Source ◽  
Shed Light

Research conducted at the Belgrade Groundwater Source in Serbia has shown that significant well screen clogging processes take place under reduced oxic and initial anoxic conditions. Criteria for the prevention, or deceleration, of clogging are becoming more relevant to well ageing, compared with classical, mechanical clogging criteria and the permissible entrance velocities derived from them. The research project was later expanded to encompass other alluvial sources, which feature distinct oxic conditions. This paper presents some of the outcomes of this project, which shed light on the correlation between certain important indicators of well screen clogging (such as the redox potential and iron concentration) and the rate of increase in local hydraulic resistance at the wells.

EPS Production during Adaptation of Acidithiobacillus ferrooxidans to High Ferric Ion Concentration

2013 ◽  
Vol 825 ◽  
pp. 115-119 ◽  
Author(s):  
Albert Saavedra ◽  
Beatriz Pavez ◽  
Mauricio Diaz ◽  
Juan Carlos Gentina
Keyword(s):  
Acidithiobacillus Ferrooxidans ◽  
Ferrous Iron ◽  
Ferric Iron ◽  
Iron Concentration ◽  
Laser Scanning Microscopy ◽  
Ion Concentration ◽  
Ferric Ion ◽  
Growth Behaviour ◽  
Ion Concentrations ◽  
Iron Concentrations

The ability ofAcidithiobacillus ferrooxidansto get its energy from the oxidation of ferrous iron and the inhibitory effect of high ferric iron concentrations on its growth behaviour has been extensively studied. Furthermore it is known thatA. ferrooxidansexudes organic substances called extracellular polymeric substances (EPS), which could play a role in its protection against adverse environmental conditions. In this context, the aim of this work was to study the production of EPS during adaptation ofA. ferrooxidansto high ferric ion concentrations. The experiments were performed in shake flasks of 250 mL at 30 °C, 200 rpm and at an initial pH of 1.8. In order to establish the natural tolerance of the strain, its growth behaviour was evaluated at high ferric iron concentrations by adding consecutively the equivalent of 9 g/L of ferrous iron each time it was depleted in the broth. Cell growth stopped once ferric iron concentration increased up to 38 g/L. The adaptation consisted in eight sub-cultures run in parallel at initial concentrations of ferrous iron of 18, 27 and 36 g/L. The EPS was quantified as micro volumes using confocal laser scanning microscopy (CLSM), labelling the cells with propidium iodide and EPS carbohydrates with wheat germ agglutinin (WGA). During the adaptation procedure it was observed an increase in the ferric ion volumetric productivity of subcultures run with 27 and 36 g/L, as a result of cell adaptation. The amount of EPS exuded by cells was higher along with those experimental conditions having higher ferric iron concentrations. It was not detected EPS on cells grown on 9 g/L of ferrous iron. This study found that the adapted strain showed higher production of EPS at high ferric ion concentrations and higher ferric ion tolerance than non-adapted ones.

The Effect of Total Iron Concentration and Iron Speciation on the Rate of Ferrous Iron Oxidation Kinetics of Leptospirillum ferriphilum in Continuous Tank Systems

2007 ◽  
Vol 20-21 ◽  
pp. 447-451 ◽  
Author(s):  
Jochen Petersen ◽  
Tunde Victor Ojumu
Keyword(s):  
Oxidation Kinetics ◽  
Ferrous Iron ◽  
Ferric Iron ◽  
Iron Oxidation ◽  
Iron Concentration ◽  
Total Iron ◽  
Ferrous Iron Oxidation ◽  
Utilisation Rate ◽  
Kinetics Of ◽  
Total Iron Concentration

In this study the results from a systematic study of the oxidation kinetics of Leptospirillum ferriphilum in continuous culture at total iron concentrations ranging from 2 to12 g/L are reported. In all experiments the steady-state concentrations of ferrous iron were small and comparable, and at least 97% of was as ferric. Surprisingly, the specific ferrous iron utilisation rate decreased with increasing total iron concentration, while yield coefficients increased. It was noted that the biomass concentration in the reactor (as measured by both CO2 uptake rate and cell counts) dramatically increased with increasing total iron concentrations, whereas it stayed more or less the same over a wide range of dilution rates at a given total iron concentration. The experimental data was re-analysed in terms of ferrous iron kinetics using Monod kinetics with a ferric inhibition term. The results confirm that the maximum specific iron utilisation rate is itself a function of ferric iron concentration, declining with increasing concentration. It thus appears that high concentrations of ferric iron stimulate microbial growth while at the same time inhibiting the rate of ferrous iron oxidation. It is postulated that these phenomena are related, i.e. that more growth occurs to reduce the load on the individual cell, possibly by sharing some metabolic functions.

scholarly journals IRON DYNAMICS AND ITS RELATION TO SOIL REDOX POTENTIAL AND PLANT GROWTH IN ACID SULPHATE SOIL OF SOUTH KALIMANTAN, INDONESIA

2017 ◽  
Vol 17 (1) ◽  
pp. 1 ◽  
Author(s):  
Wahida Annisa ◽  
Dedy Nursyamsi
Keyword(s):  
Organic Matter ◽  
Plant Growth ◽  
Redox Potential ◽  
Rice Straw ◽  
Ferrous Iron ◽  
Block Design ◽  
Soil Redox Potential ◽  
Soil Redox ◽  
Acid Sulphate Soil ◽  
Acid Sulphate

<p>Organic matter has a function to maintain reductive conditions and to chelate toxic elements in acid sulphate soils. The study aimed to assess the dynamics of ferrous iron (Fe2+) in acid sulphate soil and its correlation with soil redox potential (Eh) and plant growth. The experiment was arranged in two factorial randomized block design with three replications. The first factor was two types of organic matter: (1) control (without organic matter), (2) rice straw and (3) rush weed (Eleocharis dulcis). The second factor was time of decomposition of organic matter: I1 = 2 weeks, I2 = 4 weeks, I3 = 8 weeks, and I4 = 12 weeks (farmer practice). The results showed that concentration of ferrous iron in the soil ranged from 782 to 1308 mg kg-1 during the rice growing season. The highest constant rate of iron reduction (k F2+) was observed on application of rice straw and rush weed with decomposition time of 8 weeks with the k Fe2+ value of 0.016 and 0.011 per day, respectively, while the ferrous iron formation without organic matter had the k Fe2+ value of 0.077 per day. The ferric iron (Fe3+) reduction served as a function of soil Eh as indicated by the negative correlation of ferrous iron and Eh (r = -0.856*). Organic matter decreased exchangeable iron due to chelating reaction. Iron concentration in roots was negatively correlated with soil soluble iron (r = -0.62*). Application of rice straw decomposed for 8 weeks increased the height of rice plant up to 105.67 cm. The score of Fe2+ toxicity at 8 weeks after planting ranged from 2 to 3, so rice crop did not show iron toxicity symptoms. </p>

Oxidation of Structural Ferrous Iron in Vermiculites: I. Oxidation by Fe3+

Clay Minerals ◽  
1988 ◽  
Vol 23 (3) ◽  
pp. 261-270 ◽  
Author(s):  
H. Graf ◽  
V. Reichenbach ◽  
B. Beyme
Keyword(s):  
Hydrogen Peroxide ◽  
Electron Transfer ◽  
Redox Potential ◽  
Cation Exchange ◽  
Ferrous Iron ◽  
Activity Ratio ◽  
Redox Potentials ◽  
Interlayer Cation ◽  
Pt Electrode ◽  
Coupled Reactions

AbstractVermiculite prepared from biotite by interlayer cation exchange was reacted with solutions exhibiting redox potentials between 625 and 765 mV. The redox potential was controlled by the Fe2+/Fe3+ activity ratio, measured with a Pt electrode, and kept constant by addition of hydrogen peroxide to balance electron transfer from structural Fe2+ to Fe3+ in solution. Oxidation of structural Fe2+ was followed by Eh-stat titration and the rate of oxidation was shown to depend on the amount of Fe3+ penetrating into interlayer positions. Consequently, it was affected not only by the redox potential, but also by the activity between Fe3+ and all other cations present in solution or in an exchangeable state. Oxidation and cation exchange are coupled reactions. In contrast to the redox potential in solution, the effective redox potential controlling the oxidation of structural Fe2+ was increased by preferential sorption of the Fe3+ ion.

Kinetics of Microbial Ferrous-Iron Oxidation by Leptospirillum Ferriphilum: Effect of Ferric-Iron on Biomass Growth

2009 ◽  
Vol 71-73 ◽  
pp. 259-262 ◽  
Author(s):  
Tunde Victor Ojumu ◽  
Jochen Petersen
Keyword(s):  
Ferrous Iron ◽  
Microbial Growth ◽  
Ferric Iron ◽  
Iron Oxidation ◽  
Iron Concentration ◽  
Biomass Concentration ◽  
Reaction Conditions ◽  
Leptospirillum Ferriphilum ◽  
Ferrous Iron Oxidation ◽  
Kinetics Of

The kinetics of microbial ferrous-iron oxidation have been well studied as it is a critical sub-process in bioleaching of sulphide minerals. Exhaustive studies in continuous culture have been carried out recently, investigating the effects of conditions relevant to heap bioleaching on the microbial ferrous-iron oxidation by Leptospirillum ferriphilum [1-3]. It was postulated that ferric-iron, which is known to be inhibitory, also acts as a stress stimulus, promoting microbial growth at higher total iron concentration. This paper investigates this phenomenon further, by comparing tests run with pure ferrous-iron feeds against those where the feed is partially oxidised to ferric at comparable concentrations. The findings clearly suggest that, contrary to reactor theory, it is indeed ferrous iron concentration in the reactor feed that determines biomass concentration and that ferric iron concentration has little effect on microbial growth. Further mathematical analysis shows that the phenomenon can be explained on the basis of the Pirt equation and the particular reaction conditions employed in the test work.

Leaching of Ni and Cu from Mine Wastes (Tailings and Slags) Using Acid Solutions and A. Ferrooxidans

2009 ◽  
Vol 71-73 ◽  
pp. 425-428 ◽  
Author(s):  
Alexa Muñoz ◽  
Denise Bevilaqua ◽  
Oswaldo Garcia Jr.
Keyword(s):  
Redox Potential ◽  
Ferric Iron ◽  
Iron Concentration ◽  
Acid Leaching ◽  
Bacterial Activity ◽  
Mine Wastes ◽  
Bacterial Leaching ◽  
Flotation Tailings ◽  
Acid Consumption ◽  
Leaching Solution

The objective of this work is to evaluate the acidic and biological leaching of tailings containing Ni/Cu from a flotation and smelting plant. Acidithiobacillus ferrooxidans, strain LR, was used for bioleaching at pH 1.8 and chemical controls were run parallel to that. The acidic leaching was done within 48 hours at pH 0.5 and 1.0. In the slag inoculated flasks the redox potential was high (600 mV), thus indicating oxidative bacterial activity, however, the obtained results after 15 days showed only around 13% Ni and 8% Cu extractions, which were not different to those of the controls. For the flotation tailings bioleaching extractions were approximately 45% for Ni and 16% for Cu while differing figures were obtained for the chemical controls. These were 30% and 12% respectively. Here we could observe that the presence of bacterial activity led to a higher solubility of Ni. Acid leaching of slag showed higher nickel and copper extractions: 56% and 24% respectively at pH 0.5 and 21% and 11% at pH 1.0. However, the acid consumption was 320 and 150 Kg/ton of slag, respectively, both much higher than in bacterial assays. These results indicated that Ni and Cu solubilization from the slag is acid dependent no matter the redox potential or ferric iron concentration of the leaching solution. For flotation tailings, acid treatment showed extractions of 23% for Ni and 16% for copper at pH 0.5 and 22% and 28%, respectively at pH 1.0. The acid consumption was also higher: 220 and 120 Kg/ton, at pH 0.5 and 1.0, respectively. Based on own findings we could observe that acid leaching is found to be more effective for slag, though the acid consumption is much higher, while for the flotation tailings, bacterial leaching seems to be the best alternative.

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