Xenon storage in porous material

Abstract

Due to its applications in electronics, commercial lighting, medical applications, and ion propulsion, Xenon (Xe) is expected to emerge as a high demand noble gas over the next few years. There are two different states in which Xenon noble gas can exist and be extracted: radioactive and non-radioactive. When the used nuclear fuel is reprocessed, radioactive Xenon gases are released as one of the volatile radionuclides. As opposed to this, non-radioactive Xenon gases are found in extremely low concentrations in the earth's atmosphere. Conventional methods of extracting Xenon gas from these states involve cryogenic distillation, which is energy-intensive and expensive. Therefore to extract Xenon gas effectively, alternative methods using adsorptive separation through Metal Organic Frameworks (MOFs) are investigated and studied. The report mainly deals with the understanding of xenon storage in porous adsorbents employing adsorption and its thermodynamic property fields. The derivations of entropy and enthalpy along with the other properties such as specific heat capacity, adsorbed phase volume and isosteric heat of adsorption help facilitate a better understanding of the adsorption process of the Xenon-MOF system beyond the usual scope of adsorption isotherms, kinetics, and pore size distribution. Based on the modified Langmuir Equation (LE) proposed by Sun and Chakraborty, parameters such as isosteric heat of adsorption at zero coverage and pre-exponential coefficient which were essential for tabulating the derived properties, were then extracted from the experimentally measured isotherms data. The project provides a theoretical insight to understand the thermal energy storage in a confined space including the entropy flow and generation, which are required to design the proposed Xe storage system. The thermodynamic property surfaces are presented graphically with respect to the changes in pressures, temperatures, and uptakes. In addition, the temperature-entropy maps show a closed loop indicating continuous thermal storage during charging and discharging of Xe gas.