Captura de gases resultantes da queima do carvão por folhas de grafeno: um estudo computacional

Abstract

Multilayer graphene based nanostructures have shown excellent potential as advancing separation membranes. Specifically, the sequestration and sieving of water and air pollutants are promising technologies that can help the future of the humanity. In this way, we employ extensive Molecular Dynamics simulations to study the pressure drive permeation of a mixture of two pollutant gases, carbon dioxide (CO2) and sulfur dioxide (SO2), through a graphene based membrane. The membrane was constructed with three parallel graphene sheets and placed at the center of the simulation box, a parallelepiped with sides 50.0 Å x 50.0 Å x 200.0 Å in x, y and z-directions, respectively. The separation dz between the sheets was varies from 5.0 Å or 20.0 Å, and the pore opening in the sheets was fixed in 10.0 Å. The system is composed by 1000 gas molecules, initially placed at the left of the membrane. and a external force generated by a pressure gradient is applied to create a flow trough the graphene nanosheets. The molecules were modeled using standard atomistic models from the literature, and the simulations were performed using the ESPREsSo package. The temperature was fixed in 300 K using the Langevin thermostat, and the equations of motion were integrated using the Velocity-Verlet algorithm. We study the system with distinct fractions of CO2 and SO2 molecules, and analyze how the nanosheet porosity and the layer separation between the graphene sheets will affect the filtration properties. Our results show that more than 90% of the gas molecules were adsorbed or blocked by the membrane, regardless the fraction of pollutants. Even applying a high pressure difference DP = 0.1 GPa, much higher than the osmotic pressure used in the experiments, the gas molecules were blocked. This indicates that the membranes are highly effective for CO2 and SO2 adsorption regardless the applied pressure.