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Thirty soil samples were collected from different locations in Siwa Oasis, Egypt. The activity was measured with a γ-ray spectrometer using a scintillation detector with a NaI(Tl) crystal, 3 × 3 inch. The average activity concentrations of 226Ra, 232Th, and 40K in the soil are 22 ± 2, 12 ± 0.6, and 158 ± 8 Bq kg–1, respectively. In addition, the radiological hazards were calculated for the investigated samples. The average values of radiological hazards affecting the population were 60 Bq kg–1, 27.5 nGy h–1, 33.7 mSv year–1, 0.16, 0.22, 0.44, and 1.18 × 10–4 for the radium equivalent activity, absorbed γ-dose, effective dose, external and internal hazard indices, gamma index, and excess lifetime cancer risk (ELCR), respectively. According to the results obtained, all samples would not present significant radiological hazards. [ABSTRACT FROM AUTHOR]

The present study focuses on the distribution of natural radionuclides and the determination of radioelement favorability in the Nugrus mylonite rock. The radionuclide contents were measured with a NaI(Tl) detector. The concentrations of U, Th, Ra (in terms of eU), and K in the mylonite studied range from 27 to 247 ppm, from 96 to 377 ppm, from 11 to 166 ppm, and from 1.14 to 3.12%, with the averages of 100 ppm, 201 ppm, 55 ppm, and 2.1%, respectively. The interelement relationships indicate that the radioelement distribution is not only magmatic but also hydrothermal. Variations of migration parameters for uranium indicate fluctuations in physicochemical conditions that lead to U accumulation and leaching processes, which are confirmed by increments and decrements in uranium concentrations. The examined samples demonstrate disequilibrium, with eU/Ra (eU) ranging from 1.32 to 3.26, with an average of 1.95, which suggests uranium addition. Uranium, thorium, and potassium favorability indices of the investigated mylonite rocks indicate moderate favorability of these rocks for uranium and thorium and high favorability for potassium. The F-parameter illustrates the presence of different stages of alterations. Mineralogical investigation indicates the presence of such radioactive minerals as thorite and Uranothorite, of Nb–Ta minerals (columbite and ishikawite), and of zircon and xenotime. [ABSTRACT FROM AUTHOR]

Ferrugination, sericitization, desulfitization, chloritization, and kaolinitization of hydrothermal origin are the main wall rock alterations occurring within the NNW shear zones at Abu Rusheid area. The secondary uranium minerals occur as hair-like radiated spots and thin micaceous flakes with canary and yellow color, which are deposited along the small cracks and microfractures of altered gneiss and lamprophyre dyke and coat surfaces of hematitized rock. The radiometric measurements proved that the uranium content increases from sericitized gneiss (average 317.9 ppm) to ferruginated gneiss (average 863.1 ppm) and then to altered lamprophyre dyke (average 1352.7 ppm). The latter is the most radioactive zone along the NNW shear zones and is considered as a good trap for the uranium leached from the host rock due to the high ability of iron oxides and clays to adsorb radioactive elements from their solutions. Therefore, the present work focuses on the uranium leaching from Abu Rusheid area using sulfuric acid. The effect of sulfuric acid concentration, liquid/solid ratio, contact time, and leaching temperature on the leaching efficiency has been investigated. The data obtained show that about 74.0% of uranium can be leached successfully under the following conditions: sulfuric acid concentration 4 M, liquid/solid ratio 10 mL/g, room temperature, 6.0 h. The leaching kinetics is well interpreted with shrinking core model with control by diffusion through a porous product layer. The diffusion-controlled process is characterized by the activation energy of 6.3 kJ mol–1. [ABSTRACT FROM AUTHOR]

An efficient natural bioextractant, orange peel extractant, was applied to recover uranium as one of hazardous elements. Batch experiments were carried out to determine the effect of various factors on the uranium extraction using a synthetic standard solution. These factors include the diluent type, pH, solvent concentration, contact time, and temperature. Under the optimum conditions (pH 4, A/O = 3/1), the maximum saturation capacity of the orange peel extractant for uranium reaches approximately 54.5 mg/g. The extracted uranium ions were almost completely eluted with NaCl/H2SO4 (1 M each). The procedure was applied to real sulfate leach liquor of a clay stone sample from Southeastern Sinai, Egypt. [ABSTRACT FROM AUTHOR]