A study was made of the resistance of incorporated Cs+ to ion exchange and of the mobility and diffusion coefficient of Cs in minerals. The minerals were synthesized in solutions and were washed with de-ionized water. Two sets of experiments were conducted to test the resistance of Cs+ to ion exchange. In the first set, Cs+ was exchanged three times at 80C by 0.5N Na+, K+ or Ca2+. The Cs remaining in minerals was quantified after acid digestion. In the second set, the Cs+ desorption kinetics were studied using 0.1M Na+ as the ion exchanger. The Cs concentration in the solution phase was measured as a function of time for 23 days. Most of the incorporated Cs+ (94-99%) in LTA zeolite and allophane was readily exchangeable with Na+ or K+. The fraction of desorbed Cs+ was also affected by the exchanging ions; the ion with lowest dehydration energy (K+) was the most effective in replacing Cs+. The ions had to partially dehydrate to access the cages of the minerals. The results of the desorption kinetics experiments showed that Cs+ desorbed quickly from LTA zeolite and the Cs+ diffusion coefficient was close to that in solution; i.e., about 10-9m2/s. Solid-state NMR analysis also provided evidence for the high mobility of Cs+ in LTA zeolite.

Cesium Incorporation and Diffusion in Cancrinite, Sodalite, Zeolite, and Allophane. J.Mon, Y.Deng, M.Flury, J.B.Harsh: Microporous and Mesoporous Materials, 2005, 86[1-3], 277-86