SORPTION AND DESORPTION BEHAVIOR OF CO-60, SR-85, AND CS-137 IN A POROUS TUFF - MECHANISMS AND KINETICS

Abstract

Sorption experiments of Co-60, Sr-85 and Cs-137 were carried out to study sorption characteristics onto a porous tuff. Sorption kinetics and rate controlling step were examined. The effects of Particle size on sorption and distribution ratio were also investigated. Desorption experiments were carried out by using extracting reagents to distinguish sorption mechanisms such as reversible sorption in groundwater condition, ion exchange, association with ferro-manganese oxides or oxyhydroxides, and irreversible fixation. Strontium sorbed onto the tuff surface mainly by the ion exchange reaction which was fast and reversible. Cobalt and cesium do not sorb by simple step. The main sorptive binding of cobalt was the association with ferro-manganese oxides and the secondary one was the irreversible fixation. Diffusion into the lattice of rock minerals controlled the sorption rate of cobalt. The main sorption of cesium was the irreversible fixation, secondary one was the ion exchange.