الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The analytical data of the studied phosphorites analysis show that, phosphorus pentoxide concentration ranges from 17.18% to 32.16% with an average about 25.36%, uranium content reaches 30ppm to 100ppm with an average of about 66.35ppm, total REEs content ranges from 172.44ppm to 291.40 with an average of about 262ppm. The total geological reserve of the Nile Valley region estimated by the Egyptian Minerals Resources Authority (EMRA, 2007) is about 1500 million tons of phosphorites. Data processing using the obtained data show that the Nile Valley phosphorites have phosphorus pentoxide reserves that can be estimated with about 380.400.000 ton, uranium reserves estimated about 99.525 ton and total REEs estimated with about 393.000 ton. The uranium was considered as strategic and economic element, so the leaching and recovery of U represent a main target of this study. Microbial leaching methods are being increasingly introduced for metal recovery from their low-grade ore and concentrates that cannot be processed economically by conventional methods. Bioleaching process including four main mechanisms as acidolysis, complexolysis, redoxolysis and bioaccumulation. Acidolysis is the main principal mechanism in bioleaching of metals where, the fungus and bacterium produce varieties of organic acids as citric acid, oxalic and gluconic acids during the bioleaching. In the present work, the bioleaching process was achieved under the optimized conditions. The U leaching efficiency reaches 85.83%. As a matter of fact, uranium was the first to be directly precipitated from bioleach liquor after a rising its pH to 7.5 using 10% NaOH. The product (U-precipitate) was identified through Environmental Scanning Electron Microscopic investigation.