Authors:Ali El-Atrash, A. Kandil, E. Souaya, and W. Georgy
The extraction of Co2+ from a 0.1M ionic strength acetate buffer by acetylacetone, and a mixture of acetylacetone and pyridine or triethylamine
was investigated at various temperatures. The enthalpy and entropy change data for the synergistic extraction support a model
in which the Co2+ ion in the acetylacetonate complex expands its coordination number from four to six in order to accomodate the two N-base
molecules. The steric hindrance caused by triethylamine is also reflected in the thermodynamic data.
Authors:S. H. Kandil, A. S. El-Kady, M. A. El-Gamal, and S. E. Morsi
Thermomechanical analysis, TMA, was used to evaluate the linear thermal expansion coefficient,α, of four different types of dental amalgams: Conventional lathe-cut alloy, conventional spheralloy, high copper dispersalloy and high copper ternary alloy. Dynamic thermal expansion studies showed an interesting contraction behaviour around 85 °C for conventional amalgams and 105 °C for high copper amalgams which coincided with the endotherms produced by differential scanning calorimetry, DSC, and was attributed to the existence of theγ2 andγ1 phases, respectively. Pure single phases were prepared and characterized by DSC at 210 °C forγ2 and 120 °C forγ1. When theγ2 was enriched with mercury, the decomposition endotherm showed gradual shift to lower temperatures and reached 85 °C. The value of the linear coefficient of thermal expansion ranged between 15 and 35 ppm/°C for all the investigated brands.
Authors:S. Kandil, B. Scholten, Z. Saleh, A. Youssef, S. Qaim, and H. Coenen
The radiochemical separation of no-carrier-added zirconium from proton irradiated yttrium was studied by two techniques, namely,
ion-exchange chromatography using Dowex 50W-X8 and Dowex 21K resins, and solvent extraction using HDEHP and TPPO, the latter
reagent being employed for the first time for separation of radiozirconium from bulk of yttrium. Out of all those techniques,
the solvent extraction using TPPO was found to be the best: the separation yield of radiozirconium was >97%, the time of separation
was short, the contamination from the long-lived 88Y activity was low (10−4%) and the final product was obtained in the form of oxalate. The production of 89Zr and 88Zr of high radionuclidic and chemical purity via irradiation of yttrium targets with protons of energies 12 and 20 MeV, respectively,
is described. The experimental yields of the two radionuclides were found to be 28 MBq/μA·h and 1.63 MBq/μA·h, respectively.
Each value corresponds to about 80% of the respective theoretical yield.
Authors:Ashraf Mohamed, H. Amer, S. Shawky, M. El-Tahawy, and A. Kandil
Water hyacinth (Eichhornia crassipes) is known to accumulate elements from rivers and a good tool for water monitoring. To test the usefulness of such an aquatic
plant as a bioindicator, we have determined the levels of Na, Ca, Cr, Fe, Co, Zn, As, Rb, Zr, Sb, Cs, La, Ce, Nd, Sm, Eu,
Tb, Yb, Hf, Ta, Th, and U in water hyacinth around industrial facilities and along the studied area by instrumental neutron
activation analysis. The concentrations of Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Cd, and Pb were determined in upstream river water
and effluent factories. Contamination factor, and pollution load index was calculated. The results show that higher concentrations
as well as bioaccumulation factors of these elements were observed in water hyacinth samples around the industrial facilities.
On the other hand a decrease in calcium concentration was observed as a result of the thermal pollution of Nile river water.
The pollution load index for the studied area was estimated to be 4.2.