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Uranium Bioleaching from a Low Grade Ore

Rashidi, Abbas | 2012

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 42835 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Roosta Azad, Reza; Safdari, Jaber
  7. Abstract:
  8. In this work, bioleaching was used to extract valuable uranium from a low grade ore. Bioleaching experiments were carried out in batch cultures using a native strain of Acidithiobacillus ferrooxidans. Experiments were conducted to investigate the effects of rotation speed, initial redox potential, initially added Fe concentration, particle size, pH, temperature, pulp density, and culture type. In the shake flask systems, over 99% of the uranium was bioleached in 48 hours at some conditions. Uninoculated flasks gave only around 25% leaching. At each study, uranium and iron concentrations, solution oxidation– reduction potential and pH were measured. The results showed that 150 rpm, d80=100 m, pH=2.0, 35oC, and pure culture of Acidithiobacillus ferrooxidans were the optimum level of studied factors. Initial redox potential didn't any effect for the high recovery achievement. Optimum initial Fe concentration was depended on pulp density. 100% uranium recovery was achievable at the studied range of pulp density. The effect of pH, pulp density and time on uranium recovery was also investigated with response surface methodology. Analysis of these results showed that a modified quadratic model was significant for consideration of these three parameters effects. Interaction of pH and pulp density was appeared in the model. Kinetics of uranium bioleaching was formulated as an electrochemical process. An equation for uranium bioleaching rate was achieved and rate constants were calculated based on experimental data. A mathematical model based on the experimental data was developed for the process. The model assumes ferric ion mediated leaching of uraninite, and cell growth with ferrous ion as substrate. The model predictions were compared with the experimental data.

  9. Keywords:
  10. Bioleaching ; Oranium ; Response Surface Methodology ; Kinetics Study ; Modeling

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