ABSTRACT
Speciation of vanadium elements in the presence of δ-alumina in aqueous media was studied to simulate the environmental impact of soil/sediment-water interacted system. Factors affecting this process are pH, presence of humic acid, and δ-alumina concentrations as an abundant sediment/soil components. Different species of both vanadium and surface of δ-alumina were deduced theoretically using MintaqA2 programme. Due to the effect of pH, the anionic species of vanadium at pH 1-3 is prevailed and changed to cationic species at pH range 6-10 at different levels of alumina. Additionally, based on the effect of alumina concertation, high percent uptake, almost 100% was found at 10.0 g/1 concentration of alumina while at level of 0.2 g/1 alumina, the maximum adsorption of vanadium was become 91%. The effect of humic acid on the speciation behavior of vanadium (V) was also studied and compared with that of vanadium (IV) based on XANES (X-ray absorption near edge structure). Adsorption behaviors were studied at concentration 4.71E-4M for vanadium at 0.1M ionic strength. The mechanism of vanadium adsorption in the presence of alumina under the same working conditions was studied and explained based on TLM (Triple layer model) where the results proved good validation and verification of the practically produced data.
ABSTRACT
In Egyptian black sands, monazite is a precious mineral characterized by its composition, which includes crucial constituents such as thorium, trace amounts of uranium, and rare earth elements. It is essential to evaluate and quantify the extent of gamma-ray exposure resulting from the presence of primordial radionuclides. This necessity arises from human activities that extract and retrieve raw materials in uranium and thorium mining operations. The current study focuses on the radiological assessment of Monazite raw material in various grades and calculates the associated hazard indices. A hyper pure Germanium detector (HPGe) determined the particular activity. For grade, 90% Monazite samples, the average activities for 232Th, 238U, and 40K were 348,008 ± 1406, 69,299 ± 2086, and 27,510 ± 245 Bq/kg, respectively. For grade 75% Monazite samples, the average activities were 219,000 ± 901, 55,000 ± 500, and 18,300 ± 86 Bq/kg, while for grade 50% Monazite samples, it was 43,294 ± 1549, 9593 ± 629, and 4000 ± 211 Bq/kg for the same element, respectively. Also, 138La's inherent radioactivity was taken into account. The computed effective and absorbed dosages exceed the worker's exempt limit of 20 mSv/y. The calculated hazard parameters are higher than the maximum recommended limits. Therefore, it is imperative to employ radiation safety measures to mitigate the potential hazards of ionizing radiation.
ABSTRACT
Bagasse pith (BP) has been utilized for activated carbon preparation using H(3)PO(4) (BPH) or KOH (BPK) as a chemical activating agent followed by carbonization at 500 degrees C. The physicochemical properties of activated carbon were carried out. The effectiveness of carbon prepared in adsorption of Rhodamine B (RhB) has been studied as a function of adsorbent type, pH, particle size, agitation time, temperature, initial dye concentration, and desorption. The results obtained showed that the adsorb ability of (RhB) to the BPH is higher than that of the BPK carbon by approximately 10 folds (198.6 and 21.5 mg g(-1), respectively). Kinetic studies show that the adsorption of RhB proceeds according to the pseudo-second-order. The intra-particle diffusion was identified to be the rate-limiting step in addition to the film diffusion. The adsorption was analyzed using 5 isotherm models (Langmuir, Freundlich, Temkin, Harkins-Jura, and Halsey isotherm equations). The highest values of r(2) were obtained with Langmuir (0.997). The adsorption capacity, q(m,) was 263.85 (mgg(-1)) at initial pH 5.7 for the particle size 0.25 nm and equilibrium time of 240 min at a temperature of 20 degrees C and initial dye concentration range of 100-600 (mg l(-1)). Temperature effect proves that the adsorption is endothermic with DeltaH=4.151 (kJ mol(-1)), DeltaS=65.786 (J mol(-1)K(-1)) and a decrease in Gibbs energy (DeltaG=-7.939 to -26.729 kJ mol(-1)). Desorption studies were carried out using water medium, HCl and NaOH with desorption of 2.7, 5.4 and 7.8%, respectively of adsorbed RhB confirming the chemical adsorption mechanism of the dye. This adsorbent was found to be both effective and economically viable.
