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Showing 2 results for Acidithiobacillus Ferrooxidans
Cu biorecovery from electronic wastes without daily pH adjusting using Acidithiobacillus Ferrooxidans

Volume 2, Issue 1 (6-2018)
Abstract
Electronic wastes are known as the most important solid wastes in 21th century. They are producing two or three time faster than other solid waste streams. Many researchers studied bioleaching of e-wastes using Acidithiobacillus ferrooxidans. The presence of alkaline metals cause e-wastes show an alkalinity nature. By adding e-wastes to the environment the pH of solution increases sensibly. Many researchers supposed the optimal pH range of A. ferrooxidans which is 1.5-2.5 as the optimal pH range to reach maximum recovery. So in the bioleaching process by daily pH adjusting in the range and using sensible amount of sulfuric acid, control the pH of solution about 2. In this research two same experiments, just the pH of one of them was adjusted daily, were done. In both experiments the environmental situation including pulp density of 15 g/l, inoculum 10% (v/v), the temperature of 30ºC, and shaking rate of 130 rpm was the same. For 25 days Cu recovery, bacterial count, pH, and Eh were examined. The results showed the maximum Cu recovery at the sample without pH adjusting was about 100% but at the sample with pH adjusting recovery was reduced to 90%. The bacterial count diagram showed the bacterium is well active in both experiments. To maximize recovery, reducing acid consumption, and increasing process economy there is no need to adjust the pH of solution.
Assessment of Optimal Iron Concentration in the Precipitation of Jarosite and the Activity of Acidithiobacillus Ferrooxidans
N. Eftekhari , M. Kargar ,
Volume 9, Issue 4 (12-2018)
Abstract
Aims: Acidithiobacillus ferrooxidans is one of the most important microorganism in bioleaching. During this process, biooxidation of iron leads to precipitation of jarosite. Jarosite decreases copper bioleaching efficiency. The aim of this study was to investigate the iron concentration in the precipitation of jarosite and the activity of Acidithiobacillus ferrooxidans.
Materials and Methods: Acidithiobacillus ferrooxidans was cultivated in 9k medium containing ferrous sulfate (Fe2+) with concentrations of 5, 10, 20, 30, and 50g/100ml and also jarosite seed medium with concentrations of 5 and 10g/l. The iron concentration was assessed by atomic absorption. Jarosite was analyzed by Fourier-transform infrared spectroscopy (FTIR) and X-ray crystallography (XRD) methods.
Findings: The cell count of Acidithiobacillus ferrooxidans, in Fe2+ concentrations of 5, 10, 20, 30, and 50g/100ml was 5×107, 2.5×108, 1.5‍×107, 10×107, and 7×107cell/ml, respectively. The jarosite precipitation rate in concentrations of 5, 10, 20, 30, 50g/100ml was 1.80, 6.09, 10.90, 16.65, and 28.8g. The minimum rate of jarosite precipitation was in 10g/100ml of Fe2+ concentration. Jarosite precipitation rate increased by increment of Fe2+ concentration and it was parallel with decrease of Acidithiobacillus ferrooxidans cell count in concentrations of 5 and 10g/l of jarosite seed; the jarosite precipitation rate was 3.13 , 3.68g. However the growth of Acidithiobacillus ferrooxidans was better than the absence of jarosite seed.
Conclusion: The optimal concentration of Fe2+ in 9K medium is 10g/100 ml. In this condition, the maximum growth rate of Acidithiobacillus ferrooxidans and minimal precipitation of jarosite exist.
 

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