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  • Author or Editor: S. Aksoyoglu x
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Abstract  

The sorption-desorption of uranium (VI) on Grimsel granite of Switzerland was studied under oxidizing conditions with an initial uranium concentration range of between 9.7·10–7 and 4.5·10–4M, using a batch technique. The sorption coefficients varied between 8.0 and 0.4 ml/g and sorption was not fully reversible. The data could be fitted to a Freundlich isotherm. By fitting the data with the Dubinin-Radushkevich equation, a mean energy of sorption of 10.7 kJ/mol was calculated, which corresponds to the energy of ion exchange reactions. The kinetic data could be interpreted by assuming diffusion into the crushed granite particles. The calculated pore diffusion coefficient was between 2.0·10–11–7.7·10–11 m2/s.

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Abstract  

As part of the laboratory support program for the field migration experiment at the Grimsel Test Site (GTS) in the Swiss Alps, the sorption behaviour of cesium on Grimsel mylonite was studied. Batch sorption experiments were carried out in N2 atmosphere (<3 ppm O2). The adsorption isotherms were reversible and non-linear for cesium concentrations of between 3.2·10–8 and 5.0·10–4M. Two different sites appear to be involved in sorption depending on whether Cs loading was high (10–6–10–3 meq/g) or low (10–7–10–6 meq/g). At low Cs loadings adsorption was considered to occur mainly at the crystal edges of mica particles. Selectivity coefficients for exchange between cesium and potassium were calculated for different Cs loadings. It was suggestd that by varying the potassium concentration of the solution and by making some assumptions, a Kd value for cesium at the migration site could be estimated. Data were fitted to both Freundlich and Dubinin-Radushkevich isotherms. The empirical Freundlich parameters enabled a site distribution function to be calculated and a mean energy of sorption of about 12 kJ/mol was found using Dubinin-Radushkevich isotherms approach.

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Abstract  

Batch sorption experiments using nickel have been carried out on marl, a sedimentary, carbonaceous rock. All experiments were performed with a synthetic water of pH 7.3 and in an atmosphere of N2/1% CO2. Over the equilibrium nickel concentration range of 10–11–10–5M, sorption was linear and reversible with Rd of 819 ml g–1. Owing to the linear sorption behavior, Rd was independent of rock/water ratio (r/w=1/5–1/100). The data suggested that at [Ni] lower than 10–7M an isotope exchange mechanism operated, whereas at higher [Ni], sorption involved ion exchange. Sorption experiments on some of the components of marl indicated that nickel adsorbs mainly on the clay minerals and on the trace of iron hydroxide present; sorption on calcite and quartz was low.

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Abstract  

Neutron activation analysis was used in the determination of thirteen trace element concentrations in clays from various regions of Turkey. Comparison of results in terms of enrichment factors with those of lignite samples from the same regions revelaed no significant correlation between clay and lignite concentrations. Structural effects as well as local soil composition seem to affect the enrichment.

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Abstract  

Batch sorption experiments with237Np using kaolinite and molasse clays were carried out under oxic conditions. The sorption kinetics and the effects of particle size of clay samples, concentration of neptunium in the solutions and the pH below and above the point of zero charge of the clays on the sorption coefficients were studied. The sorption coefficients of neptunium, on kaolinite were between 23 and 1100 ml/g at pH 1.5 and 7.6, respectively, whereas, sorption on the molasse clay was not affected significantly by pH (Rd 600 ml/g).

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Abstract  

Precise, absolute
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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.
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