الفهرس 
Review of LiteratureOnly 14 pages are availabe for public view
Abstract
In this study, three rock samples were collected from Um Bogma formation, East Abu Zenema, southwestern Sinai, Egypt. Two samples (I and II) were collected from two different locations in Wadi Nasab and one sample (III) was collected from Um Hamd mountain. Sample’s physical and chemical properties were analyzed using many techniques and instruments such as X-Ray Diffraction, SEM-EDX, Flame Atomic Absorption, spectrophotometer and ICP-OES. The samples were rich in heavy metals and radionuclides. They also showed low organic matter content.
Total count of the microorganisms present in the studied samples was done at 37 °C and 55 °C and the microbial count was low and was inversely proportional to heavy metals’ content and directly proportional to organic matter content. A number of 10 actinobacterial isolates (all belong to the genus Streptomyces) and 10 fungal isolates (all belong to the genus Aspergillus) were isolated from the studied rock samples.
Sample III (collected from Um Hamd mountain) showed the highest uranium concentration and was chosen for the biotransfer studies. Biotransfer studies were conducted which included bioleaching, biosorption, biomineralization and bioaccumulation. Two-step agitation bioleaching experiments were done using cells and cell metabolites. Isolate FII-5 showed the highest bioleaching efficiency (85 %) using the indirect technique. It was identified as Aspergillus niveus EGY2. In case of actinobacteria, isolate AII-6 also showed the highest bioleaching efficiency (64 %) using the indirect technique. It was identified as Streptomyces sp. EGY1. There was a weak positive correlation between U-bioleaching efficiency in case of the indirect and direct techniques.
Biosorption of U was measured after desorption from cells used in the direct bioleaching experiments. The highest fungal isolate in U-biosorption was Aspergillus candidus (FII-1) and the highest actinobacterium was Streptomyces sp. (AII-7) that could make biosorption of U up to 33.5 and 12.41 ppm g-1 dry weight, respectively.
Streptomyces sp. (AII-6) and A. medius (FII-2) were subjected to microscopic examination using light microscope and SEM-EDX analysis. They formed biogenic mineral crystals which didn’t have a definite shape or composition.
Aspergillus niveus EGY2 accumulated U inside their cells along with other elements such as Si, Ca and Fe, which was observed after examination of the pellets obtained from one-step agitation bioleaching experiment using TEM-EDX. U was also found adsorbed on the surface of the cells and precipitated beside them as a part of a biogenic mineral.
The twenty isolates were tested for acid production on a basal medium. All the tested fungi and actinobacteria produced acid(s) except isolates AI-1, AII-2 and AIII-2. All the tested fungi have higher API than most of the tested actinobacteria. Isolate A. candidus (FII-4) had the highest API which was 4.76. There was a weak to moderate positive correlation between acid production and U-bioleaching efficiency in case of the indirect and direct techniques, respectively.
The tested actinobacteria and fungi were screened for their phosphate solubilization activity on Pikovskaya’s agar and their efficiencies were compared by means of PSI. Only 5 actinobacterial isolates (AII-1, AII-4, AII-5, AII-7 and Streptomyces sp. EGY1) and 2 fungal isolates (FII-2; A. medius and FII-4; A. candidus) were phosphate solubilizers. There was a very weak to weak negative correlation between PSI and U-bioleaching efficiency in case of the indirect and direct techniques, respectively.
Different variables were tested for their effect on U-bioleaching using culture filtrate of Aspergillus niveus EGY2. The conditions that yielded the highest bioleaching efficiency were pH 9, 160 rpm of both the culturing and the bioleaching steps, particle size of above 700 µm and 1% pulp density. The highest U-bioleaching efficiency obtained was 97.1% (1818 ppm).
A waste (sugar cane molasses) was tested for suitability to use in the indirect bioleaching of U using Aspergillus niveus EGY2. It proved to be suitable and the optimal concentration of molasses for U-bioleaching was 4% where U-dissolution efficiency reached 89.19%.
A bench-scale column reactor was designed and set up for U-bioleaching using Aspergillus niveus EGY2. It showed smaller efficiency (19.78% within 48h) than agitation leaching.
One-step direct bioleaching experiment was conducted using Streptomyces sp. EGY1 and Aspergillus niveus EGY2, then leach liquor was analyzed for the concentration of radionuclides using gamma ray spectroscopy. The results indicated the presence of a different concentrations of the isotopes of U and the biotransfer percentage of the lighter isotope of U was greater than the heavier isotopes in case of Streptomyces sp. EGY1 vice versa in case of Aspergillus niveus EGY2.
A direct measurement of the isotopic composition of uranium in uranyl acetate solution treated with the tested microorganisms and a control sample (Natural Isotopic composition 238U 99.3% and 235U 0.7%) was done using MGAU code. The results showed a bias toward the declared 235U value with a very low effect of the used isolates on the percentage of 235U. There was a certain trend undertaken by the tested actinobacteria opposite to that by the tested fungi which caused the estimated 235U values to shift above and below the declare value, respectively.
Uranium was recovered from leach liquor using sodium hydroxide. The precipitate showed co-precipitation of many contaminating elements. U was precipitated in the form of autunite (instead of sodium urinate) and its concentration was high (64.35%). Calcium oxalate mineral crystals were also present in the precipitate.