(30b) Advanced Sorbent Materials for Noble Gas Separation

Separation of volatile radionuclides (noble gases) from the off-gas streams of a used nuclear fuel reprocessing facility has been a topic of significant research. The current technology uses energy intensive cryogenic distillation, which is expensive. Another downside of this technology is the accumulation of ozone due to radiolysis of oxygen. Therefore alternate materials/technologies are needed for separation of Xe/Kr from process off-gases at near room temperature. In this regard, Pacific Northwest National Laboratory is exploring organic (porous organic cages), inorganic (Zeolites) and hybrid materials (metal organic frameworks, covalent organic frameworks and porous organic polymers) for separation of Xe and Kr at near room temperature. Our laboratory results demonstrate the removal Xe and Kr with high adsorption capacity and selectivity compared to benchmark materials such as activated carbons. The extraordinary selectivity towards Xe/Kr at low concentration indicates the perfect match between the pore size and the kinetic diameter of the gas molecule. Though these materials shown to be very promising for removal of noble gases from off-gas, one fundamental issue impeding the large-scale deployment of MOFs in commercial and industrial applications is the high pulverulent properties. In general, shaping of sorbents for off-gas processes improves handling and reduces the pressure drop for flow systems. Our recent work shows how to shape MOF powders into engineered form.