Monte Carlo simulations of adsorption and separation of binary mixtures of CO_2, SO_2, and H_2S by charged single-walled carbon nanotubes

摘要

Grand-canonical Monte Carlo simulations were carried out to investigate the adsorption and separation of the binary mixture of CO2, SO2, and H2S in neutral and charged armchair single-walled carbon nanotubes (SWCNTs) at low pressures and 303 K. SWCNTs with diameter of 2.17, 2.71, and 3.26 nm and intertube distance of 1.0 nm were modeled. Fixed charges of -0.04 e to +0.04 e were placed on each nanotube carbon to investigate the effect of charge. It is found that the behaviors of CO2, SO2, and H2S as a component of the mixture in charged SWCNTs basically obey the same rules as they behave as pure gases. Due to the additional strong Coulomb force between the adsorbate and the charged SWCNTs, the adsorption quantity of the polar molecule (SO2 or H2S) are enhanced remarkably when mixed with CO2, while the adsorption of CO2 is usually suppressed as a result of adsorption competition in a limited space. As for the case of the mixture of SO2 or H2S, either of them can be enhanced or suppressed in the adsorption competition, depending on the sign of SWCNT charge.