(343d) Removal of Low Concentration Radioactive Noble Gases Using Metal-Organic Frameworks-a Column Breakthrough Study

Metal-organic frameworks (MOFs) are novel porous materials which have potential applications in gas adsorption and separation. Radioactive isotopes of xenon (Xe) and krypton (Kr) exist in the off-gases from nuclear power plants and they need to be removed to prevent radiation pollution, especially Kr due to its long half-life isotope ⁸⁵Kr. Two metal-organic framework materials were investigated to determine the removal efficiency and capacity of MOF materials for krypton removal from air at non-cryogenic temperatures. Our two bed breakthrough measurements on the Ni/DOBDC and a partially fluorinated FMOF-Cu indicate these MOF materials can capture and separate parts per million levels of Xe and Kr from air. Moreover, the removal efficiencies and adsorption capacities for Kr on these two MOFs were further increased after Xe was removed in the first bed to reduce competitive adsorption. In addition, the FMOF-Cu showed a Kr adsorption capacity of 1.03 mmol/kg at 40 ppm and 233 K, which is one of the highest values reported in the literature. This extraordinary capacity is possibly due to a temperature gate effect known to the FMOF-Cu. Our results show a promising future for MOFs in a radioactive nuclides separation from spent fuel.