Fundamentals of vapors adsorption onto activated carbon fibers assessed by the comparative analysis of N2 and CO2 adsorption

The study of the adsorption of gaseous hazardous CH3OH, C6H6 and CCl4 onto activated carbon fibers (ACFs) was analysed by comparative analysis of N2 and CO2 adsorption. The study of the adsorption of the mentioned molecules at low concentrations, with the exception of CO2, has proved the existence of diffusion restrictions to enter inside the narrow microporosity, even at room temperature, which is related with the adsorption process at low pressures. Therefore, due to diffusion restrictions to access the narrow microporosity, the use of ACF to remove vapors a very low concentration must be carefully stretched. On the other hand, CO2 adsorption is a necessary complementary technique for a complete analysis of the porous texture. N2 and CO2 adsorption data constitute the most suitable combination since both molecules have a similar polarizability, size and geometrical form, and thus, for the same adsorption potential, the two of them adsorb in micropores of the same size.

Graphical abstractThe comparison between the characteristic curves corresponding to the adsorption of N2, CO2, C6H6, CCl4 and CH3OH allows us to demonstrate that there are diffusion restrictions for the entering of these molecules, with the exception of CO2, inside the narrow microporosity, even at room temperature. The analysis of the experimental conditions at which diffusion restrictions occur indicates that they can be related with the adsorption at low pressures, because in these conditions the diffusion of molecules inside of micropores is a slow process.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The adsorption gaseous hazardous onto ACF analysed from the adsorption N2 and CO2. ► Gas molecules shows diffusion restrictions to enter inside the narrow microporosity. ► The diffusion of molecules inside of micropores is a slow process at low pressures.