Canonical Monte Carlo simulation of adsorption of O2 and N2 mixture on single walled carbon nanotube at different temperatures and pressures.

Adsorption of pure and mixtures of O(2) and N(2) on isolated single-walled carbon nanotube (SWCNT) have been investigated at the subcritical (77 K) and different supercritical (273, 293, and 313 K) temperatures for the pressure range between 1 and 31 MPa using (N,V,T) Monte Carlo simulation. Both O(2) and N(2) gravimetric storage capacity exhibit similar behaviors, gas adsorption is higher on outer surface of tube, compared to the inner surface. Results are consistent with the experimental adsorption measurements. All adsorption isotherms for pure and mixture of O(2) and N(2) are characterized by type I (Langmuir shape), indicating enhanced solid-fluid interactions. Comparative studies reveal that, under identical conditions, O(2) adsorption is higher than N(2) adsorption, due to the adsorbate structure. Excess amount of O(2) and N(2) adsorption reach to a maximum at each temperature and specified pressure which can be suggested an optimum pressure for O(2) and N(2) storage. In addition, adsorptions of O(2) and N(2) mixtures have been investigated in two different compositions: (i) an equimolar gas mixture and (ii) air composition. Also, selectivity of nanotube to adsorption of O(2) and N(2) gases has been calculated for air composition at ambient condition.