Herein, an in-situ DRIFT technique was used to study the reaction mechanism of methanol dehydration to dimethyl ether (DME). Moreover, the effect of silver loading on the catalytic performance of η-Al2O3 was examined in a fixed bed reactor under the reaction conditions where the temperature ranged from 180-300 °C with a WHSV= 48.4 h-1. It was observed that the optimum Ag loading was found to be 10% Ag/η-Al2O3 with this novel catalyst also showing a high degree of stability under steady-state conditions and this is attributed to the enhancement in both the surface Lewis acidity and hydrophobicity.

Radon (222 Rn) generated within the grains of rocks, soils, building materials and other materials by the radioactive decay of radium ( 226 Ra) can migrate to the atmosphere. This paper reviews the emanation coefficient, diffusion coefficient, and exhalation rate, and the factors that control the rate at which radon can enter atmosphere. The emanation coefficient which is the fraction of radon generated within the grains of materials and escaped to the pore space, varied from 2.1 to 32% for rocks, from 0.14 to 80% for soil, and from 0.10 to 58% in case of building materials. In addition, measurement methods used to evaluate emanation coefficient and its influence factors are also reviewed. The diffusion of radon is a process determined by radon concentration gradient across the radon sources and the surrounding air. The effective diffusion coefficient of some materials is summarized. Moreover, the radon exhalation rate process and the main influencing factors on the variation of exhalation rate data are reviewed. The exhalation rate varied in the range of 0.11 to 80 mBq m -2 s -1 , 2.0 10 -3 to 5.0 10 4 mBq m -2 s -1 and 4.0 10 -3 to 5.0 10 1 mBq m -2 s -1 for rocks, soils and building materials, respectively.

No abstract

No abstract

No abstract

Radionuclide concentrations of uranium (238 U), thorium (232 Th) and potassium (40 K) maintained in 10 phosphate ore and 5 fertilizer samples were measured using a high-purity germanium detector. The concentrations of these radionuclides in the phosphate ore samples were relatively high for 226 Ra at 871.37 ± 91.90 Bq kg −1 and relatively low for 232 Th and 40 K at 19.21 ± 2.42 Bq kg −1 and 176.06 ± 17.66 Bq kg −1 , respectively. The concentrations of these radionuclides were low in the fertilizer samples. The radiological hazards of the radium equivalent activity (Ra eq), external (H ex) and internal (H in) indices and annual effective dose due to the presence of these radionuclides in the investigated samples were calculated. The released radon from the selected samples was measured using the Alpha Guard radon monitor. Subsequently, the radon emanation coefficient and its exhalation rate were calculated.

Radionuclide concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in different types of building materials used in Egypt were measured using gamma-ray spectroscopy. The results showed relatively moderate radionuclide concentrations for all samples except granite, which showed extremely high concentrations of 78.75 ± 2.36, 2.82 ± 0.11 and 2.37 ± 0.07 kBq kg⁻¹ for ²²⁶Ra, ²³²Th and ⁴⁰K, respectively. The radiological hazard indexes of radium equivalent activity (Raeq), external hazard index (Hex) and internal hazard index (Hin), due to the presence of those radionuclides in the investigated building materials, were calculated. The released radon from the selected samples was measured using the AlphaGUARD radon monitor in order to use its value to calculate the radon emanation coefficient and the radon exhalation rate. The alpha equivalent dose (dose from indoor radon generated from building materials) was calculated using the measured values of the radium concentration and the radon emanation coefficient.

In this study, in-situ and laboratory γ-ray spectroscopy techniques were compared to evaluate the activity concentration of natural radionuclides in soil. The activity concentrations of U (Ra), Th, andK in the soil in 11 sites were simultaneously measured with in-situ portable HPGe and the NaI(Tl) detectors. In parallel, 55 soil samples collected from these sites were analyzed with a laboratory γ-ray spectroscopy technique (HPGe). A strong correlation was observed between the in-situ and laboratory HPGe techniques with a linear correlation coefficient (R) of 0.99 for Ra andTh and 0.975 for K, respectively. The in-situ HPGe technique shows a strong correlation with the NaI(Tl) detector. γ-Rays cps ofRa, Th, andK of the NaI (Tl) detector were then converted to specific activities (Bq kg unit) in soil using the empirical formulas obtained in this study. The absorbed dose rate in air at 1 m height above ground due to these radionuclides was calculated using the Beck's formula and the results were compared with measured values obtained with an high pressure ionization chamber. The results of the calculated and measured dose rate show a strong correlation of R = 0.96. The reliability and precision of analytical spectroscopy techniques of radioactivity and radiation dose were confirmed in this work.