Optimizing Isolated Nanotubes for Noble Gas Storage and Separation Applications

The adsorption performance of 2169 types of nanotubes for noble gas (Xe, Rn, Kr, and Ar) storage and separation (Kr/Ar, Rn/Xe, Xe/Ar, and Xe/Kr) was evaluated using grand canonical ensemble molecular simulations, through adsorption isotherms, adsorption heats, and selectivity analysis under varying pressures and nanotube types. Boron nitride nanotubes (BNNTs) and silicon carbide nanotubes (SiCNTs) demonstrated the highest adsorption capacities and selectivity across most gas systems. For instance, the Xe adsorption capacity in BNNTs ranges from 5.7 to 8.8 mmol/g at 1.0 MPa, while Rn adsorption in SiNTs reaches 17-20 mmol/g. For Kr and Ar, BNNTs also perform exceptionally, with capacities of 3.3-6 and 1.8-4.1 mmol/g, respectively. Adsorption heat analysis shows Rn having the highest adsorption heat (17-33 kJ/mol), followed by Xe, Kr, and Ar. In binary gas separation systems, BNNTs and SiCNTs exhibit significantly higher selectivity for Xe/Ar and Xe/Kr systems compared to other nanotubes. Adsorption configuration analysis reveals capillary condensation in the Rn/Xe system at low pressures, while the Xe/Ar and Xe/Kr systems remain unsaturated, indicating room for further optimization. These findings offer valuable insights for improving nanotube designs in noble gas storage and separation applications.