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Abstract The potential applications of biotechnology like bioleaching, biosorption and bioaccumulation processes in the field of metal extraction from its ores, looks very promising, have an important echo in the world, especially for uranium. Whereas, recent research showed the importance of using microorganisms in the operations of leahing and extracting valuable elements. This study aimed to investigate the effect of radionuclides on the microorganisms, which found naturally in the uraniferous rock samples. Moreover, study the effect of these microorganisms upon the uranium leaching process from its ores, which collected from Um Bogma Formation, southwestern Sinai, Egypt. Therefore, the present study was concerned with the mechanisms of biotransformation of radionuclides and toxic metals were briefly discussed with the view of using such a knowledge-base for developing novel biometallurgy strategies. Microorganisms, in the environment, are needed for a complete life cycle, which many species may be under appropriate circumstances from multicellular structure, sometimes with morphological and metabolic differentiations between the various cells making up a bio-structure. Growth by cell division is the most common way of microorganism propagation. They are characterized by their almost infinite ability to biodegradation and biosynthesis naturally occurring compound in the environment. Microorganism reactions control, partly or fully, the chemical composition of many, very different environments such as sediments, soil, lakes and Abstract xx ground water. Furthermore, they have the ability to adapt to extreme environments such as alkaline and acidic ground water. Modern methods and techniques were used to achieve the aim of this study; after the bioleaching process of uranium by the chemical methods and radiometrically using High purity germanium detector (HPGeD) - Analysis by X-ray Diffraction (XRD) to determine the mineral change of the rock samples through the stages of study – Environmental scanning Electron Microscopy (ESEM) and the Energy Dispersive Analytical X-ray unit (EDAX), also optical and spectral methods were used. The sediment was analyzed by bio-polarized microscope to differentiate between the crystallization and amorphous structures. The identification of the chemical composition was occurred by using ESEM. Moorganisms play an important and a major role in the mobilization and immobilization of radionuclides and toxic metals by direct enzymatic or indirect non-enzymatic actions. They could affect the chemical nature of the radionuclides by altering the speciation, solubility and sorption properties and thus could increase or decrease the concentrations of radionuclides in solution. Nine grapped samples were collected, two samples from the lower member, four samples from the middle member, and three samples from the upper member of lower Carboniferous Um Bogma Formation, southwestern Sinai, Egypt. After isolation and purification processes of microorganisms from the tested samples, nine fungal species were identified according to their morphological features. The fungal strains are belonged to three species and known as Abstract xxi - Aspergillus species, contains five genera were identified, Aspergillus niger, A. fumigatus, A. flavus, A. terreus and A. oryzae. - Penicillium species, contains three genera were Penicillium steckii, P. Italicum, P. diversum - Mucor species, contains one type. In this work, all the fungal strains investigated were found to exhibit lower leaching efficiency except A. niger and A. terreus were achieved high leaching efficiency 57% and 42% respectively. The optimum conditions influencing uranium bioleaching process by both fungi were 7days as the incubation period, 30 ºC as incubation temperature, initial pH value equal 3 and 3% pulp density of the ore material. In these conditions, the uranium leaching efficiency using A. niger and A. terreus reached 80% and 60% respectively. The recovery of uranium using A. niger reached up to 71.4 % of the lowest uranium grade sample. The recovery of uranium has been performed by proper precipitation to obtain a concentrate with high quality containing 98% pure uranium. from the recovery process, the obtained bioprecipitate analyzed by polarized light microscope, which could differentiate between the crystallized and amorphous forms. The chemical composition of each is identified by environmental scanning electron microscope. Examination of the produced bioprecipitate by X-Ray Diffraction (XRD) technique identified as uranyl acetate hydrate (C4H4O6U.2H2O) well, its formation ascribed to the bio-dissolution of uranium from the original sample Abstract xxii (dolomite). Furthermore, the formation of some complexes with acetic acid that secreted from the A. niger and creating the uranyl acetate hydrate. Consequently, the rest of the dolomite complex with the iron (in the original sample) forming ankerite mineral [Ca (MgO.67 FeO.33) (CO3)2]. Under bioleaching condition uranium complexed with organic ligand (acetic acid) are reduced to uranium (IV)-acetate. Distribution of the different radionuclides (i.e. 238U, 226Ra, 232Th, 235U and 40K) under the previous optimum conditions were studied in this work, the bioleaching efficiency was bound to increase with the decreasing uranium concentration. One of the important results is the bioleaching of some radionuclides as 226Ra, 214Bi and 214Pb which did not achieve by the traditional acid leaching technique. Through the bioleaching process, selective leaching for several radionuclides are exhibited; whereas, A. niger able to leach 70-80% 238U, 40-60% 226Ra and 70-78% 235U. on the other hand, A. terreus specified for 232Th, which achieved 32-74% leachability of the studied samples. It appears from our study of uranium bioleaching process, that a reduction in the final pH was occurring from 6.5 to 3. This reduction was accompanied by the production of high quantities of organic acids as a secondary metabolite in the growth media of tested fungal strains, which have an appreciable and effective role in uranium solubility. These organic acids identified as: - Formic; acetic; citric and oxalic acids in the case of A. niger. Abstract xxiii - Citric, oxalic, galic, malonic and ascorbic acids by using A. terreus. The obtained results proved that: (1) The acetic acid has an important role in bioleaching process by using A. niger strain, whereas it increased by increasing the pulp density and could form organo-complex with uranium (uranyl acetate) appeared in XRD of the product. (2) The formic acid decreased by increasing the ore concentrations with A. niger strain. (3) The common agent between the two fungal strains A. niger and A. terreus secretion was oxalic acid, which has slight changes with an increase the ore concentrations for A. terreus strain, on the contrary, for A. niger strain. Moreover, all secreted organic acids decreased except acetic acid has an appreciable increase to 18 mg/ml in case of A. niger. On the other hand, secretions of oxalic acid by A. terreus in the growth media are increased to 19 mg/ml at 1% ore concentration and decreased to 16 mg/ml by increasing the ore concentration to 5%. Furthermore, citric and aascorbic are secreted only at control value which are found to be 6.96 and 7.9 mg/ml, respectively, and disappeared with increasing the ore concentration in the growth media. The adaptation of A. terreus strain with the surrounding medium are achieved by secreting malonic and galic acids, where malonic acid was found with 12.69 mg/ml at 1% sample concentration and decreased to 7.92 mg/ml at 5% sample concentration, while galic acid was secreted with 5.67 mg/ml only at 5% sample concentration. During the bioleaching process, the biosorption take place. from the measuring of the biosorption controlling factors, the Abstract xxiv optimum conditions occurred at 5% ore concentration, 9 days incubation period, 35 ºC and pH 9 were achieved the maximum biosorption efficiency for A. niger and A. terreus. The morphological investigations, in this study, showed several changes of A. niger during their development accordingly in the primary stegmata, it became shorter in their length than the control, while the secondary stegmata are disappeared by increasing the ore concentrations in the growth media. Furthermore, the changes in conidial diameters exhibited to be increased when the fungus grown at 1% and 5% sample (A-3) concentrations, and its number is decreased with increasing ore concentration in the growth media. By using the transmission electron microscope for A. niger is grown upon Dox agar medium containing different ore concentrations (control, 3%, 5%, 7% and 9%); the substantial changes upon the cell membrane permeability for the different metal ions in the surrounding medium occurred. The obtained result showed that: - The ultrastructure changes of the cell wall increase with increasing ore concentration. - High accumulation and precipitation of various elements are displayed in black dense areas around the cell wall - Large vacuoles and partial distortions like inner cell wall irregularity are formed at 3%, 5% and 7%. - The shrinkage of cellular structures is clearly appeared with increasing the ore concentration. Abstract xxv - Finally, at 9% ore concentration, the ability of an organism to tolerate more concentration of toxic metals is decreased and succeeds to diffuse inside the cell causing highly deformation of cellular structure causing their degradation and disappearance. from the obtained results of this work mention that using the microorganisms in the uranium leaching considered as one of the most promising technology to extract the valuable elements from its rich ores than the traditional methods. Consequently; recommended for use the bioleaching process, in addition to increasing the studies in the direction of the effect of microorganisms to dissolve the precious radionuclides. |