H. N. Erten

Thermodynamic parameters of Cs+ sorption on natural clays

The sorption behavior of Cs+ on kaolinite, chlorite-illite, and bentonite clays as a function of time, cation concentration, and temperature was studied using the radiotracer method. Sorption data were well represented by Freundlich and Dubinin-Radushkevich type isotherms. Bentonite was found to have the highest sorption capacity and the highest exchange affinity to Cs+. In all three cases Cs+ sorption was found to be exothermic with DH° (kJ/mol) –13, –8, –19 and DS° (J/mol.K) –15, 31, and –3 for kaolinite, chlorite-illite, and bentonite, respectively. Negative DG° values were obtained in all cases, indicating the spontaneity of sorption. The magnitudes of DG° suggest that ion exchange is the primary sorption mechanism.

Sorption of radioiodine on organic rich soil, clay minerals and alumina

Batch method was used to investigate the sorption behavior of radioiodine on organic rich soil, alumina, chlorite-illite clay mixture and bentonite.131I was used as tracer. The grain sizes of the samples used were all below 38 μm. A rather slow kinetics was observed for the adsorption of radioiodine on organic rich soil. The distribution ratio increased with increasing solution/solid (V/m) ratio, and the contact time. The pH of the synthetic groundwater did not change the distribution ratio appreciably. The soil biomass however, showed a striking effect on the adsorption of radioiodine. Among the clay minerals, the highest distribution ratio value was found for chlorite-illite clay mixture. All the values were however well below those of the organic rich soil. The sorption data were fitted to Freundlich and Dubinin-Radushkevich types isotherms. Means energies of adsorption, as well as the affinity ratios of the sorption sites to iodine and chlorine were calculated.

RADIOCHEMICAL STUDY OF CO2+ SORPTION ON CHLORITE AND KAOLINITE

In this work, the sorption behavior of Co(II) ions on natural chlorite and kaolinite as a function of time, concentration and temperature was studied.60Co radiotracer method and the batch technique were used. The kinetic results indicated that about one day of contact time was enough to achieve equilibrium. The sorption process was described by Freundlich type isotherms. Sorption of Co(II) ions on both clays was found to be endothermic with ΔH0 (kJ/mol) and ΔS0 (kJ/mol·K) being 33 and 0.14 for kaolinite and 17 and 0.102 for chlorite, respectively. The magnitudes of the corresponding ΔG0 values suggest that sorption occur mainly via an ion exchange mechanism on both clays.

Radiochemical studies of the sorption behavior of strontium and barium

The sorption behavior of strontium and barium on kaolinite, bentonite and chlorite-illite mixed clay was studied by radioanalytical techniques using the batch method.90Sr (29.1 y) and133Ba (10.5 y) were used as radiotracers. Characterization of the solid matrices was done by FTIR and XRD spectrometries and specific surface area measurements. Synthetic groundwater was used as the aqueous phase. The variation of the distribution ratioRd, as a function of metal ion loading was examined. The sorption isotherms were fitted to various isotherm models. The sorption energies were calculated to be in the range of 8–10 kJ/mol suggesting an ion exchange type of sorption mechanism. In detailed experiments, chlorite-illite mixed clay was first presaturated with K+, Sr2+, Ca2+ and Al3+ ions, respectively, prior to sorption studies with Ba2+ ions. The results of Ca2+ pretreated chlorite-illite were very similar to those of natural chlorite-illite, suggesting that the Ba2+ ion exchanges primarily with the Ca2+ ion on the clay minerals.

Efficiency calibration and summation effects in gamma-ray spectrometry

AbstractPrecise, absolute γ-ray efficiences (∈γ) and total efficiences (∈T), have been measured at various distances from the detector, using a set of standards. The observed linear variation of∈γ and∈T as well as∈γ/∈T with Eγ and

Determination of trace element levels in human scalp hair in occupationally exposed subjects by XRF

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Uptake of Ba2+ ions by natural bentonite and CaCO3: A radiotracer, EDXRF and PXRD study

provides a simple means of interpolation and extrapolation. Experimental coincidence summation effects were determined for various nuclides and compared with calculated values. The results are found to be in good agreement with each other.

Isomeric yields of130Sb,132Sb,134I, and136I in the thermal neutron fission of235U

The210Pb and137Cs profiles of sediment cores from two locations in southern Spain, three locations in southern Turkey and two locations in northern Cyprus were determined by direct γ-ray spectroscopy. Sedimentation rates were derived for all locations using the210Pb data. The rates range from 1.39±0.12 cm · y−1 (0.50±0.04 g · cm−2 · y−1) to 0.08±0.01 cm · y−1 (0.039±0.003 g · cm−2 · y−1). Except for one core, the137Cs profiles were also used to compute sedimentation rates. The results are in good agreement with those of210Pb values. The results of the Constant Initial Concenration and Constant Rate of Supply dating models are in good agreement with each other. The flux of unsupported210Pb varies between 0.11±0.03 to 0.74±0.01 pCi · cm−2. The average depositional flux was found to be considerably lower for cores from the Eastern Mediterranean.