Influence of ageing on the catalytic activity of ferric sludge for oxidation of fe(II)

1998 ◽  
Vol 38 (6) ◽  
pp. 129-137 ◽  
Author(s):  
Nese Tufekci ◽  
Hasan Z. Sarikaya
Keyword(s):  
Catalytic Activity ◽  
Continuous Flow ◽  
Ferrous Iron ◽  
Catalytic Effect ◽  
Ferric Iron ◽  
Iron Oxidation ◽  
Ferric Hydroxide ◽  
Oxidation Rate Constant ◽  
Batch Systems ◽  
Oxygenation Rate

The catalytic effect of freshly formed or added ferric iron on the Fe(II) oxidation has been demonstrated by previous studies. High Fe(III) concentrations significantly accelerate the oxygenation rate. High Fe(III) concentrations can be maintained only by sludge recycle which eventually leads to sludge ages as high as 10 days. Therefore, the aim of this study was to determine whether ageing of ferric hydroxide sludge affects its catalytic effect on the oxidation of ferrous iron by aeration. In order to reach this aim four different groups of experiments were carried out using ferric hydroxide sludge aged for a period of 0 to 10 days. Initial Fe(III) concentrations were varied within the range of 50 mg/l to 200 mg/l. It has been demonstrated that the catalytic effect of ferric hydroxide sludge on the oxidation of ferrous iron by aeration increases with increasing sludge age contrary to what is commonly expected. It has been concluded that, catalytic oxidation rate constant kcat obtained from the batch systems can safely be used in design of continuous flow iron oxidation reactors with sludge recycle.

scholarly journals Ferrous Iron Is a Significant Component of Bioavailable Iron in Cystic Fibrosis Airways

mBio ◽  
2013 ◽  
Vol 4 (4) ◽  
Author(s):  
Ryan C. Hunter ◽  
Fadi Asfour ◽  
Jozef Dingemans ◽  
Brenda L. Osuna ◽  
Tahoura Samad ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Ferrous Iron ◽  
Ferric Iron ◽  
Relative Proportion ◽  
Iron Oxidation ◽  
The United States ◽  
Environmental Parameter ◽  
Content Type

ABSTRACTChronic, biofilm-like infections by the opportunistic pathogenPseudomonas aeruginosaare a major cause of mortality in cystic fibrosis (CF) patients. While much is known aboutP. aeruginosafrom laboratory studies, far less is understood about what it experiencesin vivo. Iron is an important environmental parameter thought to play a central role in the development and maintenance ofP. aeruginosainfections, for both anabolic and signaling purposes. Previous studies have focused on ferric iron [Fe(III)] as a target for antimicrobial therapies; however, here we show that ferrous iron [Fe(II)] is abundant in the CF lung (~39 µM on average for severely sick patients) and significantly correlates with disease severity (ρ = −0.56,P= 0.004), whereas ferric iron does not (ρ = −0.28,P= 0.179). Expression of theP. aeruginosagenesbqsRS, whose transcription is upregulated in response to Fe(II), was high in the majority of patients tested, suggesting that increased Fe(II) is bioavailable to the infectious bacterial population. Because limiting Fe(III) acquisition inhibits biofilm formation byP. aeruginosain various oxicin vitrosystems, we also tested whether interfering with Fe(II) acquisition would improve biofilm control under anoxic conditions; concurrent sequestration of both iron oxidation states resulted in a 58% reduction in biofilm accumulation and 28% increase in biofilm dissolution, a significant improvement over Fe(III) chelation treatment alone. This study demonstrates that the chemistry of infected host environments coevolves with the microbial community as infections progress, which should be considered in the design of effective treatment strategies at different stages of disease.IMPORTANCEIron is an important environmental parameter that helps pathogens thrive in sites of infection, including those of cystic fibrosis (CF) patients. Ferric iron chelation therapy has been proposed as a novel therapeutic strategy for CF lung infections, yet until now, the iron oxidation state has not been measured in the host. In studying mucus from the infected lungs of multiple CF patients from Europe and the United States, we found that ferric and ferrous iron change in concentration and relative proportion as infections progress; over time, ferrous iron comes to dominate the iron pool. This information is relevant to the design of novel CF therapeutics and, more broadly, to developing accurate models of chronic CF infections.

Continuous biological ferrous iron oxidation in a submerged membrane bioreactor

2005 ◽  
Vol 51 (6-7) ◽  
pp. 59-68 ◽  
Author(s):  
D. Park ◽  
D.S. Lee ◽  
J.M. Park
Keyword(s):  
Ferrous Iron ◽  
Membrane Bioreactor ◽  
Ferric Iron ◽  
Iron Oxidation ◽  
Membrane Module ◽  
Microbial Oxidation ◽  
High Density Culture ◽  
Submerged Membrane Bioreactor ◽  
Ferrous Iron Oxidation ◽  
Iron Oxidizing Bacteria

Microbial oxidation of ferrous iron may be available alternative method of producing ferric iron, which is a reagent used for removal of H2S from biogas. In this study, a submerged membrane bioreactor (MBR) system was employed to oxidize ferrous iron to ferric iron. In the submerged MBR system, we could keep high concentration of iron-oxidizing bacteria and high oxidation rate of ferrous iron. There was membrane fouling caused by chemical precipitates such as K-jarosite and ferric phosphate. However, a strong acidity (pH 1.75) of solution and low ferrous iron concentration (below 3000 mg/l) significantly reduced the fouling of membrane module during the bioreactor operation. A fouled membrane module could be easily regenerated with a 1 M of sulfuric acid solution. In conclusion, the submerged MBR could be used for high-density culture of iron-oxidizing bacteria and for continuous ferrous iron oxidation. As far as our knowledge concerns, this is the first study on the application of a submerged MBR to high acidic conditions (below pH 2).

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 Secreted Pyomelanin of Legionella pneumophila Promotes Bacterial Iron Uptake and Growth under Iron-Limiting Conditions

2013 ◽  
Vol 81 (11) ◽  
pp. 4182-4191 ◽  
Author(s):  
Huaixin Zheng ◽  
Christa H. Chatfield ◽  
Mark R. Liles ◽  
Nicholas P. Cianciotto
Keyword(s):  
Legionella Pneumophila ◽  
Ferrous Iron ◽  
Iron Uptake ◽  
Iron Transport ◽  
Ferric Iron ◽  
Iron Acquisition ◽  
Ferric Hydroxide ◽  
Supernatant Fraction ◽  
Content Type ◽  
Ferrous Iron Transport

ABSTRACTIron acquisition is critical to the growth and virulence ofLegionella pneumophila. Previously, we found thatL. pneumophilauses both a ferrisiderophore pathway and ferrous iron transport to obtain iron. We now report that two molecules secreted byL. pneumophila, homogentisic acid (HGA) and its polymerized variant (HGA-melanin, a pyomelanin), are able to directly mediate the reduction of various ferric iron salts. Furthermore, HGA, synthetic HGA-melanin, and HGA-melanin derived from bacterial supernatants enhanced the ability ofL. pneumophilaand other species ofLegionellato take up radiolabeled iron. Enhanced iron uptake was not observed with a ferrous iron transport mutant. Thus, HGA and HGA-melanin mediate ferric iron reduction, with the resulting ferrous iron being available to the bacterium for uptake. Upon further testing ofL. pneumophilaculture supernatants, we found that significant amounts of ferric and ferrous iron were associated with secreted HGA-melanin. Importantly, a pyomelanin-containing fraction obtained from a wild-type culture supernatant was able to stimulate the growth of iron-starved legionellae. That the corresponding supernatant fraction obtained from a nonpigmented mutant culture did not stimulate growth demonstrated that HGA-melanin is able to both promote iron uptake and enhance growth under iron-limiting conditions. Indicative of a complementary role in iron acquisition, HGA-melanin levels were inversely related to the levels of siderophore activity. Compatible with a role in the ecology and pathogenesis ofL. pneumophila, HGA and HGA-melanin were effective at reducing and releasing iron from both insoluble ferric hydroxide and the mammalian iron chelates ferritin and transferrin.

An experimental study on iron removal with ferric sludge recycling

2000 ◽  
Vol 42 (1-2) ◽  
pp. 393-397 ◽  
Author(s):  
N. Tufekci ◽  
H.Z. Sarikaya ◽  
I. Ozturk
Keyword(s):  
Reaction Kinetics ◽  
Ferrous Iron ◽  
Natural Waters ◽  
Ferric Iron ◽  
Ferric Hydroxide ◽  
Iron Removal ◽  
Aeration Tank ◽  
Batch Reactors ◽  
High Concentration ◽  
Activated Sludge Processes

An iron removal process, which makes use of the catalytic effect of ferric iron, is proposed. For this purpose, the reaction kinetics derived from the data of the batch experiments was applied to the continuous flow system. Based upon this reaction kinetics, it has been theoretically demonstrated that the volumes of aeration tanks can be significantly reduced by keeping a high concentration of ferric iron in the reactor. However, in natural waters, Fe(II) is found commonly to be in the range of 0.01–10 mg/l. These ferrous iron concentrations are not high enough to maintain the high concentrations of ferric iron in the aeration tank. Therefore, similar to the activated sludge processes used in wastewater treatment, it is suggested that the required Fe(III) concentrations can be maintained by recycling Fe(OH)3 sludge back to the aeration tank. It is known that the oxygenation of ferrous iron is catalyzed by the reaction product, ferric hydroxide. Catalytic action of the ferric iron sludges on the oxidation of ferrous iron by aeration has been identified and the kinetics of this catalytic reaction has been formulated by the authors. The oxidation of Fe(II) was studied in batch reactors in which the concentration of Fe(III) was in the range of 0–600 mg/l. The oxygenation rate increased linearly with the increasing Fe(III) concentrations up to 50 mg/l and a second-order polynomial relationship was found between the reaction rate and the Fe(III) concentrations in the range of 50–600 mg/l. The required volume (V) of the aeration tank and the effluent Fe(II) concentrations were determined as a function of the Fe(III) concentration. The volume of the aeration tank required for the same Fe(II) conversion was reduced by a factor of 15 when the Fe(III) concentration was raised from 0 to 600 mg/l at pH=6.7. No incremental benefit of the increase of Fe(III) concentration was observed at Fe(III) levels beyond the 600 mg/l. This study has experimentally demonstrated that significant savings can be achieved in iron removal systems by recirculating the Fe(III) sludges back to the aeration tank.

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.

Resistance of Moderately Thermophilic Acidophilic Microorganisms to Ferric Iron Ions

2017 ◽  
Vol 262 ◽  
pp. 471-475
Author(s):  
Aleksander Bulaev
Keyword(s):  
Ferrous Iron ◽  
Ferric Iron ◽  
Iron Oxidation ◽  
Iron Concentration ◽  
Iron Ions ◽  
Moderately Thermophilic ◽  
Ferrous Iron Oxidation ◽  
Low Concentrations ◽  
The Media ◽  
High Concentrations

Resistance of microorganisms predominating in biohydrometallurgical processes including bacteria of the genus Sulfobaсillus and archaea of the genus Acidiplasma to ferric iron ions was studied. Capabilities of the strains for growth and ferrous iron oxidation in the media containing high concentrations of ferric iron ions (of 250 to 1000 mM) were evaluated. Ferric iron ions significantly inhibited oxidative activity and growth of the studied microorganisms. It was revealed that bacteria of the genus Sulfobacillus were not able to oxidize ferrous iron actively when ferric iron concentration exceeded 500 mM, whereas archaea of the genus Acidiplasma completely oxidized ferrous iron in the medium containing 1000 mM of Fe3+. Growth of the microorganisms was inhibited by relatively low concentrations of ferric iron. Microorganisms did not grow in the medium containing more than 750 mM of Fe3+ and cells of all studied strains lysed in presence of high concentrations of ferric iron. It was shown, that archaea of the genus Acidiplasma of the family Ferroplasmaceae were more resistant to high concentrations of ferric iron than bacteria of the genus Sulfobacillus. The results obtained are important for understanding of the regularities of the formation of microbial communities performing technological processes.

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