Sorption Behavior of Cesium in Two Greek Soils: Effects of Cs Initial Concentration, Clay Mineralogy, and Particle-size Fraction

The characteristics of Cs sorption behavior in two soils (soil 1 and soil 2) with nearly the same clay content and exhangeable K concentration, but with different clay mineralogy, were studied by the quantification of the distribution coefficient (kd). It was observed that as the initial Cs concentration increased from 4 to 50 mg L-1, the kd values decreased in both soils, suggesting a progressive saturation of Cs available sorption sites. However, the presence of expansible 2:1 phyllosilicates minerals in the clay fraction of soil 2 maintained a high Cs sorption ability for this soil, even at high Cs concentrations. The experimental data were also fitted to the Freundlich isotherm and the results showed that parameters of the Freundlich equation could be used to estimate the degree of Cs sorption and the nature of the available sorption sites. For the studied soils, the kf and the kd values followed a similar trend and the n Freundlich constant values provided a reliable indicator for the soils clay mineralogy. The removal of the sand fraction enhanced Cs sorption in both soils and the absence of sorbed Cs ions on the quartz minerals, as observed by the SEM analysis, additionally supported the effect of particle-size fraction on Cs sorption.