Complexation of uranium (VI) by different bacteria recovered from uranium mining waste piles

Radioactive wastes are classified as high-level wastes (spent fuel etc.), transuranic wastes (wastes from spent fuel reprocessing, nuclear weapons), and low- and intermediate-level wastes which are generated from a variety of activities, for instance, uranium mining. The presence of uranium in these wastes, is a major concern because of its potential to migrate from the waste repositories and piles and to long-term contaminate the environment. Therefore, it is becoming increasingly clear that such polluted sites will require a long-term stewardship in addition to remediation. Effective remediation and stewardship will require a better understanding of the environmental chemistry of uranium. Results of experimental investigations of uranium accumulation and studies of microbial ecology in uranium-rich environments strongly imply that microorganisms play significant role in uranium mobilization and immobilization. Biological processes for uranium immobilization in particular, include biosorption, bioaccumulation, precipitation, and biomineralization. In this work, we investigated the uranium sorption efficiency of different bacterial strains isolated from uranium mining wastes such as Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, Pseudomonas stutzeri, Pseudomonas migulae and the corresponding reference strains under various conditions (pH, amount of biomass, temperature). The ability of the above mentioned microorganisms to tolerate uranium and some other heavy metals was studied as well.