Study of the effect of functionalization of carbon nanotubes on gas separation

In order to improve the adsorption capacity and selectivity of CO₂/CH₄ and CO₂/N₂ , we have functionalized multi-walled carbon nanotubes (MWCNT) with 3-aminopropyltriethoxysilane (APTES). The functionalized MWCNT was characterized by Fourier transform infrared (FT-IR), energy dispersive X-ray spectroscopy (EDX) and BET analysis. CO₂, CH₄ and N₂ adsorption at two different temperatures and P < 5 bar on the functionalized MWCNTs was investigated by the volumetric method. The selectivity of the functionalized MWCNTs for CO₂/CH₄ and CO₂/N₂ was studied and compared with MWCNTs. The functionalized MWCNTs show higher adsorption capacity of CO₂ and selectivity of CO₂/CH₄ and CO₂/N₂ in comparison with the MWCNTs at different pressures. The highest CO₂/CH₄ and CO₂/N₂ selectivities for the functionalized MWCNTs were 6.78 and 26.14, respectively, at a pressure of 0.2 bar and at 298 K. Two of the most common adsorption models, the Langmuir and Sips isotherms, were used to correlate the experimental data of CO₂ and CH₄ adsorption on the adsorbents. The results confirm that the functionalized MWCNTs are promising materials for the separation and purification of gases. (author)