Role of structure and organic contaminants on Cs Sorption by clays

Long-term confinement and isolation of long-lived radionuclides from the biosphere is necessary in view of safety aspects of nuclear reactor activities. Geological materials show favorable sorption characteristics for various radionuclides resulting in their retention for a geological time-scale. In the present study, structural profile of three different clay geosorbents was evaluated using various instrumental techniques and its correlation with Cesium (Cs) sorption was investigated. Structural characterization revealed modal mineralogical variation among the three clay geosorbents. The spectroscopic analysis indicated the signature of organic matter (OM) (in particular polycyclic aromatic hydrocarbons (PAHs)) in one of the samples. Cs retention facilitated by clay geosorbents was found to be rapid, concentration dependent and non-linear. The sorption data correlated better with Freundlich isotherm than Langmuir owing to the heterogeneous nature of the sorbents. The dominance of 2:1 clay geosorbent in the Cs sorption over the 1:1 clay geosorbents was clearly observed from the batch sorption studies. In addition, the organic matter present in the clay found to influence the sorption capacity of the geosorbent. The role of structural aspects in terms of mineralogy and organic matter on the Cs immobilization over the clay geosorbents is discussed.