Variable-temperature MAS NMR spectroscopic study of incorporated and sorbed 133Cs and 23Na in zeolitic minerals
EMSL Project ID
3350
Abstract
This is a continuation of the 133Cs and 23Na NMR work (proposal 2588) have been performed at EMSL through the User Facility program. Several zeolite or zeolite-like minerals have been found in simulated reactions between sediments and the high-level radioactive waste solutions stored in the underground tanks at the Hanford site. The new mineral phases, especially the colloid sized particles, may facilitate the transport of radioactive nuclides in the vadose zone. Linede Type A (LTA) zeolite, cancrinite, sodalite and a short-distance ordered feldspathoid allophane have formed in our previous simulating experiment when Hanford tank waste solutions contacted the underlying sediment. These zeolite or zeolitic materials have negative charges in the structure and therefore they are capable of sorbing and incorporating cations such as Cs+ and Na+ in the unique cages or channel. Radioactive 133Cs has been found as a major radiation source in the tank solutions. They have been detected in much deep depth than predicted. There are several sites inside the cages or channles that Cs+ can occupy and cesium may exist as ion pairs with OH-, NO3-, NO2-, CO32-, Cl-, SO42- in the zeolitic materials. The adsorbed cesium had 40 ppm shift compared to the incorporated cesium in Linde type A zeolite at room temperature and room humidity. Similar shifts were also observed on cancrinite/sodalite lepispheric colloids. Yet the 133Cs and 23Na NMR patterns are generally simple because of the motion averaging effect. In this proposed experiment, we are planning to record the pattern at lower temperature to get the resolved peaks and make more unambiguous peak assignments. We are also going to dehydrate the samples to reduce the motion contribution from included water. A better understanding of the sites and forms of cesium in the minerals will be achieved. We expect this experiment will improve our understanding of the fate and transport of radioactive Cs in the Hanford environment. The results will be combined with our other chemical and spectroscopic data for publications.
Project Details
Project type
Capability Research
Start Date
2003-03-25
End Date
2004-04-05
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Mon J, Y Deng, M Flury, and JB Harsh. 2005. "Cesium Incorporation and Diffusion in Cancrinite, Soalite, Zeolite, and Allophane." Microporous and Mesoporous Materials 86(1-3):277-286.