Cesium Sorption to Illite as Affected by Oxalate

Abstract

Abstract Cesium uptake by plants depends on adsorption/desorption reactions in the soil, as well as root uptake processes controlled by the plant. In this study, sorption and desorption of Cs + on reference illite (IMt-1) was investigated in the presence of oxalate to gain understanding of mechanisms by which plant root exudates may influence Cs + bioavailability in micaceous soils. Cesium sorption on illite decreased significantly as oxalate concentration increased from 0.4 to 2 mM. Cesium desorption from illite increased significantly with increasing oxalate concentration. Desorption of Cs + by exchange with Na + , Ca 2+ and Mg 2+ was significantly enhanced in the presence of oxalate as selectivity for Cs + decreased with respect to these ions in the presence of oxalate. On the other hand, oxalate had little effect on the Cs + /K + selectivity coefficient. This suggests that oxalate treatments increase the relative proportion of exchange sites that are not highly selective for Cs + and K + ; e.g. ‘ planar’ sites. The results indicate that oxalate plays an important role in Cs + binding on illite and, therefore, plant rhizosphere chemistry is likely to alter Cs + bioavailability in micaceous soils.