Simulation studies of the separation of Kr-85 radionuclide gas from nitrogen and oxygen across nanoporous graphene membranes in different pore configurations

SM Fatemi and H Sepehrian and M Arabieh, EUROPEAN PHYSICAL JOURNAL PLUS, 131, 131 (2016).

DOI: 10.1140/epjp/i2016-16131-6

Separating molecular species is an important precursor for various applications. In this work, we have utilized molecular dynamics (MD) simulations to examine how pore radius and structure affect the separation process. We show from MD simulations that 2-D graphene sheets with designed sub-nanometer pores can efficiently separate the Kr-85 radionuclide gas from an N-2/O-2 mixture. Three species of gases (Kr-85, N-2 and O-2) were considered in the simulation box in which different sizes and geometries of pores were modeled on the graphene sheet. The (30 x 30 x 80) angstrom(3) simulation box contains a nanoporous graphene membrane in the middle of the box and two fixed walls with equal distances on both sides of the nanoporous graphene. The results revealed that Kr-85 separation was improved by using an optimized pore structure. It was also found that the Kr-85 gas radionuclides could be completely separated from nitrogen and oxygen molecules in the pore-7 configuration. Restriction of the molecular orientation largely prohibited the permeation of nitrogen molecules. It was also found that nitrogen was more strongly adsorbed onto the membrane than oxygen, while krypton was not adsorbed.

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