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

Abstract

The effect of organic matter and iron oxides as solid components of the red earth on the retention of SeO 3 has been investigated by a batch technique and selective extraction method. The sorption and desorption isotherms of SeO 3 on the untreated red earth and the three treated soils were determined at 20 ~ pH 6.8 or 7.2 and in the presence of0.01M CaCI 2. 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 SeO 3 on red earth is attributed to the iron oxides to a great extent.

27 Radiochemistry

“…More detailed studies in which the effect of variation of pH and carbonate ion concentrations upon the adsorption of neptunyl(V) onto hydragilite 213 and neptunyl(V) and cobalt(II) onto titania 214 have also been reported. In some cases the presence of organic matter appears to affect the adsorption of ions such as selenate 215 on soils rich in iron oxides. However, this observation may be due to the tendency of hematite to form colloids which can greatly affect the sorption characteristics of ions, as has been shown for thorium 216 and uranium.…”

Sorption of selenium oxyanions on TiO2 (rutile) studied by batch or column experiments and spectroscopic methods

“…In natural aqueous environments, selenium can be found under two stable oxidation states: Se(IV), generally as a selenite oxyanion SeO 3 2− or in its protonated forms H 2 SeO 3 and HSeO 3 − (pKa 1 = 2.64 and pKa 2 = 8.4 [3]), and Se(VI) as a selenate oxyanion SeO 4 2− . Numerous studies have investigated the sorption of selenium oxyanions on various mineral surfaces such as iron oxyhydroxides [4][5][6][7][8][9][10][11][12][13][14], aluminium oxy-hydroxides [15][16][17][18][19][20], hydrous titanium [21] or manganese [22] oxides, copper(I) oxides [23,24], cements and clays [3,[25][26][27][28][29], soils or complex media [30][31][32][33][34][35], granite [36,37], hydroxyapatite [38], Mg/Fe carbonated layered double hydroxides [39] and iron sulphides [2,40]. In most of these sorption studies , Se(IV) appeared to be more retained by the solid surface than Se(VI).…”