Batch kinetics of ferrous iron oxidation by Leptospirillum ferriphilum at moderate to high total iron concentration

2010 ◽  
Vol 50 (1-2) ◽  
pp. 54-62 ◽  
Author(s):  
Kalin Penev ◽  
Dimitre Karamanev
2009 ◽  
Vol 71-73 ◽  
pp. 255-258 ◽  
Author(s):  
K. Penev ◽  
D. Karamanev

The effects of temperature, pH and iron concentration on the kinetics of ferrous iron biooxidation by a free suspended culture of Leptospirillum ferriphilum were studied in shake flasks and a circulating bed bioreactor at moderate to high total iron concentration. The kinetic study showed that there are two distinct modes of iron biooxidation: growth associated and non-growth associated, depending on the pH of the medium. There were also distinctive maxima of the effect of temperature and pH on the rate of biooxidation. A kinetic model of the process was proposed, based on an electrochemical-enzymatic model. The proposed model indicates that at moderate to high concentrations (above ~12 g/L), the total iron concentration becomes the single most prominent inhibiting factor.


2007 ◽  
Vol 20-21 ◽  
pp. 447-451 ◽  
Author(s):  
Jochen Petersen ◽  
Tunde Victor Ojumu

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.


2009 ◽  
Vol 71-73 ◽  
pp. 259-262 ◽  
Author(s):  
Tunde Victor Ojumu ◽  
Jochen Petersen

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.


2007 ◽  
Vol 20-21 ◽  
pp. 156-159 ◽  
Author(s):  
Tunde Victor Ojumu ◽  
Jochen Petersen ◽  
Geoffrey S. Hansford

In heap bioleaching the dissolution of gangue minerals from igneous ore materials can lead to the build-up of considerable concentrations of Mg and Al sulphates in the recycled leach solution. This may interfere with microbial ferrous iron oxidation, which drives the oxidation of the target minerals. The kinetics of the oxidation process have been well studied for Leptospirillum and Acidithiobacillus species in tank systems. Although not directly comparable, kinetic parameters derived for tank systems do apply also for heap bioleach conditions. In the present study the effect of solution concentrations of Mg and Al as sulphate at individual concentrations of 0 to 10 g/L and combined concentrations 0 to 16 g/L each has been investigated in continuous culture using Leptospirillum ferriphilum. Increasing the concentrations of the salts increasingly depresses the rate of ferrous iron oxidation and also shifts the viable range more and more into the low potential region. Al significantly reduces the amount of carbon maintained in the reactor (assumed to be commensurate with biomass), whereas Mg actually enhances it at low concentrations. In both cases, however, the rate is always depressed. The results indicate that heap cultures are likely to perform sub-optimally in those operations where build-up of dissolved gangue minerals is not controlled.


2007 ◽  
Vol 20-21 ◽  
pp. 465-468 ◽  
Author(s):  
Bestamin Özkaya ◽  
Pauliina Nurmi ◽  
Erkan Sahinkaya ◽  
Anna H. Kaksonen ◽  
Jaakko A. Puhakka

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.


2005 ◽  
Vol 11 (2) ◽  
pp. 59-62 ◽  
Author(s):  
Dragisa Savic ◽  
Miodrag Lazic ◽  
Vlada Veljkovic ◽  
Miroslav Vrvic

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.


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