Understanding The Mechanism Of Gaseous Iodine Capture Using Sodium-Loaded Carbon Foams

This study highlights the potential of using a high specific surface area carbon monolithic foam with sodium as a new approach for capturing 129I, a radioactive volatile emitted during the processing of nuclear waste. Iodine is emitted during the vitrification processing of low activity waste at the Hanford site as the glass melt is heated to above 1,000°C, and iodine incorporated into the nuclear waste vaporizes at 184°C. Monolithic sodium-carbon foams were successfully synthesized from commercially available melamine formaldehyde sodium bisulfite foams. The foams were found to effectively capture iodine as sodium iodide in both a static iodine saturated environment and in a simulated off-gas environment with low concentrations of iodine, high gas velocities, and low resonance times. The synthesized carbon foams contained sodium in the form of sodium carbonate, along with remnants of the original organic polymer, which added mechanical stability to the carbon foam. After aging in nitrogen dioxide, the capture of iodine decreased, as did the mechanical stability, which was attributed to the formation of sodium nitrate. The sodium iodide captured by the carbon foams can be incorporated into a stable final waste form, such as iodasodalite glass, if practical methods of iodine desorption are found. Desorption tests of sodium-carbon foams by a simple water treatment shows the viability of removing the sodium iodide from the foam substrate. To evaluate the sorbent's robustness and compare to other potential iodine capture sorbents, a friability testing system was created using a quartz crystal microbalance, and no apparent mass loss from the sorbent was detected in a flowing gas environment. The widespread commercial availability, one-step carbonization process of the melamine foam, and iodine capture capacity makes monolithic sodium-carbon foams an economically viable replacement for current sorbents used in nuclear waste processing today.

Level thesis:degree_level

Master's Degree

Year dc:date.issued

2022

Author dc:creator

• Elliott, Casey

Advisor dc:contributor.advisor

• Carlson, Krista

Committee members dc:contributor.committeemember

• Chidambaram, Dev
• Menezes, Pradeep

• carbon foam
• hanford
• iodine
• vitrification

Handle dc:identifier.uri

http://hdl.handle.net/11714/8572

OAI identifier oai:identifier

oai:scholarwolf.unr.edu:11714/8572