Sorption and desorption of radioselenium on calcareous soil and its solid components studied by batch and column experiments

The effect of different calcareous soil solid components on the sorption and desorption of radioselenium was investigated by using a selective extraction method. The distribution coefficients, the breakthrough curves and the displacement curves were experimentally determined by batch and column experiments. The experiments were carried out at pH 7.8±0.2, T=20±1°C and in the presence of 0.001 M CaCl2. It is found that all sorption isotherms are linear, the sorption-desorption hysteresis for untreated and treated soils to remove organic matter, CaCO3 and organic matter plus CaCO3 is obvious; and the retention of radioselenium can probably be attributed to clay and oxides. The contributions of organic matter and CaCO3 to the sorption of radioselenium are significant, and the interaction effects among organic matter, CaCO3 and other components play an important role in the sorption of radioselenium in calcareous soil. The content of interlaminary space of compacted soil plays an important role in the sorption of radioselenium in compacted soil. The presence of CaCO3 retards the transport of radioselenium in soils, CaCO3 is an important trap of radioselenium. It is very difficult for the effluent concentration to reach the influent concentration, although radioselenium is very quickly detected in the effluent solution. The breakthrough curves (BTCs) can be simulated by a one-dimensional convection-dispersion transport model.