Sorption and desorption of radioselenium on red earth and its solid components

The effect of organic matter and iron oxides as solid components of the red earth on the retention of SeO₃ has been investigated by a batch technique and selective extraction method. The sorption and desorption isotherms of SeO₃ on the untreated red earth and the three treated soils were determined at 20°C, pH 6.8 or 7.2 and in the presence of 0.01 M CaCl₂. It was found that the sorption-desorption hysteresis for untreated and treated soils is obvious and the clays play an important role in the sorption-desorption hysteresis, and that the retention of SeO₃ on red earth is attributed to the iron oxides to a great extent.