Environmental Geochemistry for Heavy Metals and Uranium Potentiality in Oil Shale Sediments, Quseir, Red Sea, Egypt

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Environmental Geochemistry for Heavy Metals and Uranium Potentiality in Oil  ShaleSediments, Quseir, Red Sea, Egypt
Hisham K. Fouad and Randa M. El-Rakaiby

Nuclear Materials Authority, P.O box 530Maadi, Cairo, Egypt

Abstract:

The environmental geochemistry of organic-rich uraniferous oil shale from Nakheil phosphate mine, Quseir area, Eastern Desert, Egypt is assessed in the present work. This shale provides an importantexample of natural geological material containing high potentially for uranium and heavy metal concentrations (Cd, Ni, Zn, V and Mo). The content of these metals exceeds the maximum permissible concentration (MPC) limits. As in most other organic-rich sediments, uranium is enriched in the oil shale where its concentration reaches 41ppm, which can be categorized as uraniferous shale. This value ofuranium is higher than the average of the continental crust (.1ppm). However, the reduction potential maintained by the organic matter of the oil shale reduces the soluble hexavalent uranium into the insoluble tetravalent one. Five stages sequential extraction procedure was used to fractionate uranium and the heavy metals; Cd, Zn, Ni, V and Mo. This distinguishes between the different binding forms of elements in oil shale. Conceptually; the solid material can be partitioned into specific fractions, which can be extractedselectively by using appropriate reagents. The sum of most elements present in the individual fractions shows a good agreement with the total elemental concentrations. Sequential extraction procedures (SEP) are operationally defined methods proposed for speciation in solid samples. Detailed scanning-electron microscope (SEM) study was carried out on the separated heavy minerals occurring in the oil shale. This study highlighted the mode of occurrence of the studied metals. Assembly of minerals as zircon of different varieties, non-radioactive monazite, apatite, pyrite, cerusite and gypsum, were also found andmanifested by the SEM.